Hematology

CHICAGO – In 2014, the average time from diagnosis to treatment initiation for new cancer patients at the Cleveland Clinic was 29-41 days, depending on whether the patient was diagnosed internally or externally. That figure was not acceptable, said Brian J. Bolwell, MD, chairman of the Cleveland Clinic’s Taussig Cancer Institute.

Since then, the time-to-treat metric has improved dramatically, dropping 33%. Today, time to treat for new cancer patients is 25-31 days, depending on the site of diagnosis.

To get there, leaders at the cancer center examined the causes of delay within each of their disease programs. The analysis revealed that less than 20% of the time it was patient preferences that slowed down the initiation of treatment, but that more than 80% of the time the delay was on the part of their institution.

Dr. Bolwell said this led them to start tracking every newly diagnosed patient who came through the cancer center to ensure they didn’t fall through the cracks, and that they were treated as rapidly as possible.

But figuring out how to get patients to treatment quicker depended on the type of cancer they had, since each type of cancer had different challenges and different points of entry to the health care system.

“So for breast cancer, it turns out a lot of the challenges might be coordination of surgery because sometimes a general surgeon has to work with a reconstructive-plastic surgeon and coordinating the surgical schedules might drastically lengthen time to treat,” he said during an interview at the annual meeting of the American Society of Clinical Oncology.

They helped address that problem by scheduling breast cancer patients for surgery by the next available operating room slot, rather than doing the scheduling by surgeon.

There are additional barriers to achieving a rapid time to treat standard, including prior authorization, Dr. Bolwell said. But they are continuing to chip away at the metric, working within each cancer type to lower the obstacles to treatment. “I don’t think we’ll ever be satisfied with where we are,” Dr. Bolwell said.

Dr. Bolwell reported having no relevant financial disclosures.

mschneider@mdedge.com

CHICAGO – In 2014, the average time from diagnosis to treatment initiation for new cancer patients at the Cleveland Clinic was 29-41 days, depending on whether the patient was diagnosed internally or externally. That figure was not acceptable, said Brian J. Bolwell, MD, chairman of the Cleveland Clinic’s Taussig Cancer Institute.

Since then, the time-to-treat metric has improved dramatically, dropping 33%. Today, time to treat for new cancer patients is 25-31 days, depending on the site of diagnosis.

To get there, leaders at the cancer center examined the causes of delay within each of their disease programs. The analysis revealed that less than 20% of the time it was patient preferences that slowed down the initiation of treatment, but that more than 80% of the time the delay was on the part of their institution.

Dr. Bolwell said this led them to start tracking every newly diagnosed patient who came through the cancer center to ensure they didn’t fall through the cracks, and that they were treated as rapidly as possible.

But figuring out how to get patients to treatment quicker depended on the type of cancer they had, since each type of cancer had different challenges and different points of entry to the health care system.

“So for breast cancer, it turns out a lot of the challenges might be coordination of surgery because sometimes a general surgeon has to work with a reconstructive-plastic surgeon and coordinating the surgical schedules might drastically lengthen time to treat,” he said during an interview at the annual meeting of the American Society of Clinical Oncology.

They helped address that problem by scheduling breast cancer patients for surgery by the next available operating room slot, rather than doing the scheduling by surgeon.

There are additional barriers to achieving a rapid time to treat standard, including prior authorization, Dr. Bolwell said. But they are continuing to chip away at the metric, working within each cancer type to lower the obstacles to treatment. “I don’t think we’ll ever be satisfied with where we are,” Dr. Bolwell said.

Dr. Bolwell reported having no relevant financial disclosures.

mschneider@mdedge.com

CHICAGO – In 2014, the average time from diagnosis to treatment initiation for new cancer patients at the Cleveland Clinic was 29-41 days, depending on whether the patient was diagnosed internally or externally. That figure was not acceptable, said Brian J. Bolwell, MD, chairman of the Cleveland Clinic’s Taussig Cancer Institute.

Since then, the time-to-treat metric has improved dramatically, dropping 33%. Today, time to treat for new cancer patients is 25-31 days, depending on the site of diagnosis.

To get there, leaders at the cancer center examined the causes of delay within each of their disease programs. The analysis revealed that less than 20% of the time it was patient preferences that slowed down the initiation of treatment, but that more than 80% of the time the delay was on the part of their institution.

Dr. Bolwell said this led them to start tracking every newly diagnosed patient who came through the cancer center to ensure they didn’t fall through the cracks, and that they were treated as rapidly as possible.

But figuring out how to get patients to treatment quicker depended on the type of cancer they had, since each type of cancer had different challenges and different points of entry to the health care system.

“So for breast cancer, it turns out a lot of the challenges might be coordination of surgery because sometimes a general surgeon has to work with a reconstructive-plastic surgeon and coordinating the surgical schedules might drastically lengthen time to treat,” he said during an interview at the annual meeting of the American Society of Clinical Oncology.

They helped address that problem by scheduling breast cancer patients for surgery by the next available operating room slot, rather than doing the scheduling by surgeon.

There are additional barriers to achieving a rapid time to treat standard, including prior authorization, Dr. Bolwell said. But they are continuing to chip away at the metric, working within each cancer type to lower the obstacles to treatment. “I don’t think we’ll ever be satisfied with where we are,” Dr. Bolwell said.

Dr. Bolwell reported having no relevant financial disclosures.

mschneider@mdedge.com

Should clinicians abandon the activated partial thromboplastin time (aPTT) for monitoring heparin therapy in favor of tests that measure the activity of the patient’s plasma against activated factor X (anti-Xa assays)?

Although other anticoagulants are now available for preventing and treating arterial and venous thromboembolism, unfractionated heparin—which requires laboratory monitoring of therapy—is still widely used. And this monitoring can be challenging. Despite its wide use, the aPTT lacks standardization, and the role of alternative monitoring assays such as the anti-Xa assay is not well defined.

This article reviews the advantages, limitations, and clinical applicability of anti-Xa assays for monitoring therapy with unfractionated heparin and other anticoagulants.

UNFRACTIONATED HEPARIN AND WARFARIN ARE STILL WIDELY USED

Until the mid-1990s, unfractionated heparin and oral vitamin K antagonists (eg, warfarin) were the only anticoagulants widely available for clinical use. These agents have complex pharmacokinetic and pharmacodynamic properties, resulting in highly variable dosing requirements (both between patients and in individual patients) and narrow therapeutic windows, making frequent laboratory monitoring and dose adjustments mandatory.

Over the past 3 decades, other anticoagulants have been approved, including low-molecular-weight heparins, fondaparinux, parenteral direct thrombin inhibitors, and direct oral anticoagulants. While these agents have expanded the options for preventing and treating thromboembolism, unfractionated heparin and warfarin are still the most appropriate choices for many patients, eg, those with stage 4 chronic kidney disease and end-stage renal disease on dialysis, and those with mechanical heart valves.

In addition, unfractionated heparin remains the anticoagulant of choice during procedures such as hemodialysis, percutaneous transluminal angioplasty, and cardiopulmonary bypass, as well as in hospitalized and critically ill patients, who often have acute kidney injury or require frequent interruptions of therapy for invasive procedures. In these scenarios, unfractionated heparin is typically preferred because of its short plasma half-life, complete reversibility by protamine, safety regardless of renal function, and low cost compared with parenteral direct thrombin inhibitors.

As long as unfractionated heparin and warfarin remain important therapies, the need for their laboratory monitoring continues. For warfarin monitoring, the prothrombin time and international normalized ratio are validated and widely reproducible methods. But monitoring unfractionated heparin therapy remains a challenge.

UNFRACTIONATED HEPARIN’S EFFECT IS UNPREDICTABLE

Unfractionated heparin, a negatively charged mucopolysaccharide, inhibits coagulation by binding to antithrombin through the high-affinity pentasaccharide sequence.^1–6 Such binding induces a conformational change in the antithrombin molecule, converting it to a rapid inhibitor of several coagulation proteins, especially factors IIa and Xa.^2–4

Unfractionated heparin inhibits factors IIa and Xa in a 1:1 ratio, but low-molecular-weight heparins inhibit factor Xa more than factor IIa, with IIa-Xa inhibition ratios ranging from 1:2 to 1:4, owing to their smaller molecular size.⁷

One of the most important reasons for the unpredictable and highly variable individual responses to unfractionated heparin is that, infused into the blood, the large and negatively charged unfractionated heparin molecules bind nonspecifically to positively charged plasma proteins.⁷ In patients who are critically ill, have acute infections or inflammatory states, or have undergone major surgery, unfractionated heparin binds to acute-phase proteins that are elevated, particularly factor VIII. This results in fewer free heparin molecules and a variable anticoagulant effect.⁸

In contrast, low-molecular-weight heparins have longer half-lives and bind less to plasma proteins, resulting in more predictable plasma levels following subcutaneous injection.⁹

 

 

MONITORING UNFRACTIONATED HEPARIN IMPROVES OUTCOMES

In 1960, Barritt and Jordan¹⁰ conducted a small but landmark trial that established the clinical importance of unfractionated heparin for treating venous thromboembolism. None of the patients who received unfractionated heparin for acute pulmonary embolism developed a recurrence during the subsequent 2 weeks, while 50% of those who did not receive it had recurrent pulmonary embolism, fatal in half of the cases.

The importance of achieving a specific aPTT therapeutic target was not demonstrated until a 1972 study by Basu et al,¹¹ in which 162 patients with venous thromboembolism were treated with heparin with a target aPTT of 1.5 to 2.5 times the control value. Patients who suffered recurrent events had subtherapeutic aPTT values on 71% of treatment days, while the rest of the patients, with no recurrences, had subtherapeutic aPTT values only 28% of treatment days. The different outcomes could not be explained by the average daily dose of unfractionated heparin, which was similar in the patients regardless of recurrence.

Subsequent studies showed that the best outcomes occur when unfractionated heparin is given in doses high enough to rapidly achieve a therapeutic prolongation of the aPTT,^12–14 and that the total daily dose is also important in preventing recurrences.^15,16 Failure to achieve a target aPTT within 24 hours of starting unfractionated heparin is associated with increased risk of recurrent venous thromboembolism.^13,17

Raschke et al¹⁷ found that patients prospectively randomized to weight-based doses of intravenous unfractionated heparin (bolus plus infusion) achieved significantly higher rates of therapeutic aPTT within 6 hours and 24 hours after starting the infusion, and had significantly lower rates of recurrent venous thromboembolism than those randomized to a fixed unfractionated heparin protocol, without an increase in major bleeding.

Smith et al,¹⁸ in a study of 400 consecutive patients with acute pulmonary embolism treated with unfractionated heparin, found that patients who achieved a therapeutic aPTT within 24 hours had lower in-hospital and 30-day mortality rates than those who did not achieve the first therapeutic aPTT until more than 24 hours after starting unfractionated heparin infusion.

Such data lend support to the widely accepted practice and current guideline recommendation⁸ of using laboratory assays to adjust the dose of unfractionated heparin to achieve and maintain a therapeutic target. The use of dosing nomograms significantly reduces the time to achieve a therapeutic aPTT while minimizing subtherapeutic and supratherapeutic unfractionated heparin levels.^19,20

THE aPTT REFLECTS THROMBIN INHIBITION

The aPTT has a log-linear relationship with plasma concentrations of unfractionated heparin,²¹ but it was not developed specifically for monitoring unfractionated heparin therapy. Originally described in 1953 as a screening tool for hemophilia,^22–24 the aPTT is prolonged in the setting of factor deficiencies (typically with levels < 45%, except for factors VII and XIII), as well as lupus anticoagulants and therapy with parenteral direct thrombin inhibitors.^8,25,26

Because thrombin (factor IIa) is 10 times more sensitive than factor Xa to inhibition by the heparin-antithrombin complex,^4,7 thrombin inhibition appears to be the most likely mechanism by which unfractionated heparin prolongs the aPTT. In contrast, aPTT is minimally or not at all prolonged by low-molecular-weight heparins, which are predominantly factor Xa inhibitors.⁷

HEPARIN ASSAYS MEASURE UNFRACTIONATED HEPARIN ACTIVITY

While the aPTT is a surrogate marker of unfractionated heparin activity in plasma, unfractionated heparin activity can be measured more precisely by so-called heparin assays, which are typically not direct measures of the plasma concentration of heparins, but rather functional assays that provide indirect estimates. They include protamine sulfate titration assays and anti-Xa assays.

Protamine sulfate titration assays measure the amount of protamine sulfate required to neutralize heparin: the more protamine required, the greater the estimated concentration of unfractionated heparin in plasma.^8,27–29 Protamine titration assays are technically demanding, so they are rarely used clinically.

Anti-Xa assays provide a measure of the functional level of heparins in plasma.^29–33 Chromogenic anti-Xa assays are available on automated analyzers with standardized kits^29,33,34 and may be faster to perform than the aPTT.³⁵

Experiments in rabbits show that unfractionated heparin inhibits thrombus formation and extension at concentrations of 0.2 to 0.4 U/mL as measured by the protamine titration assay,²⁷ which correlated with an anti-Xa activity of 0.35 to 0.67 U/mL in a randomized controlled trial.³²

Assays that directly measure the plasma concentration of heparin exist but are not clinically relevant because they also measure heparin molecules lacking the pentasaccharide sequence, which have no anticoagulant activity.³⁶

 

 

ANTI-Xa ASSAY VS THE aPTT

Anti-Xa assays are more expensive than the aPTT and are not available in all hospitals. For these reasons, the aPTT remains the most commonly used laboratory assay for monitoring unfractionated heparin therapy.

However, the aPTT correlates poorly with the activity level of unfractionated heparin in plasma. In one study, an anti-Xa level of 0.3 U/mL corresponded to aPTT results ranging from 47 to 108 seconds.³¹ Furthermore, in studies that used a heparin therapeutic target based on an aPTT ratio 1.5 to 2.5 times the control aPTT value, the lower end of that target range was often associated with subtherapeutic plasma unfractionated heparin activity measured by anti-Xa and protamine titration assays.^28,31

Because of these limitations, individual laboratories should determine their own aPTT therapeutic target ranges for unfractionated heparin based on the response curves obtained with the reagent and coagulometer used. The optimal therapeutic aPTT range for treating acute venous thromboembolism should be defined as the aPTT range (in seconds) that correlates with a plasma activity level of unfractionated heparin of 0.3 to 0.7 U/mL based on a chromogenic anti-Xa assay, or 0.2 to 0.4 U/mL based on a protamine titration assay.^32,34–36

Nevertheless, the anticoagulant effect of unfractionated heparin as measured by the aPTT can be unpredictable and can vary widely among individuals and in the same patient.⁷ This wide variability can be explained by a number of technical and biologic variables. Different commercial aPTT reagents, different lots of the same reagent, and different reagent and instrument combinations have different sensitivities to unfractionated heparin, which can lead to variable aPTT results.³⁷ Moreover, high plasma levels of acute-phase proteins, low plasma antithrombin levels, consumptive coagulopathies, liver failure, and lupus anticoagulants may also affect the aPTT.^{7,25,32,36–41} These variables account for the poor correlation—ranging from 25% to 66%—reported between aPTT and anti-Xa assays.^32,42–48

Such discrepancies may have serious clinical implications: if a patient’s aPTT is low (subtherapeutic) or high (supratherapeutic) but the anti-Xa assay result is within the therapeutic range (0.3–0.7 units/mL), changing the dose of unfractionated heparin (guided by an aPTT nomogram) may increase the risk of bleeding or of recurrent thromboembolism.

CLINICAL APPLICABILITY OF THE ANTI-Xa ASSAY

Neither anti-Xa nor protamine titration assays are standardized across reference laboratories, but chromogenic anti-Xa assays have better interlaboratory correlation than the aPTT^49,50 and can be calibrated specifically for unfractionated or low-molecular-weight heparins.^29,33

Although reagent costs are higher for chromogenic anti-Xa assays than for the aPTT, some technical variables (described below) may partially offset the cost difference.^29,33,41 In addition, unlike the aPTT, anti-Xa assays do not need local calibration; the therapeutic range for unfractionated heparin is the same (0.3–0.7 U/mL) regardless of instrument or reagent.^33,41

Most important, studies have found that patients monitored by anti-Xa assay achieve significantly higher rates of therapeutic anticoagulation within 24 and 48 hours after starting unfractionated heparin infusion than those monitored by the aPTT. Fewer dose adjustments and repeat tests are required, which may also result in lower cost.^32,51–55

While these studies found chromogenic anti-Xa assays better for achieving laboratory end points, data regarding relevant clinical outcomes are more limited. In a retrospective, observational cohort study,⁵¹ the rate of venous thromboembolism or bleeding-related death was 2% in patients receiving unfractionated heparin therapy monitored by anti-Xa assay and 6% in patients monitored by aPTT (P = .62). Rates of major hemorrhage were also not significantly different.

In a randomized controlled trial³² in 131 patients with acute venous thromboembolism and heparin resistance, rates of recurrent venous thromboembolism were 4.6% and 6.1% in the groups randomized to anti-Xa and aPTT monitoring, respectively, whereas overall bleeding rates were 1.5% and 6.1%, respectively. Again, the differences were not statistically significant.

Heparin resistance. Some patients require unusually high doses of unfractionated heparin to achieve a therapeutic aPTT: typically, more than 35,000 U over 24 hours,^7,8,32 or total daily doses that exceed their estimated weight-based requirements. Heparin resistance has been observed in various clinical settings.^{7,8,32,37–40,59–61} Patients with heparin resistance monitored by anti-Xa had similar rates of recurrent venous thromboembolism while receiving significantly lower doses of unfractionated heparin than those monitored by the aPTT.³²

Lupus anticoagulant. Patients with the specific antiphospholipid antibody known as lupus anticoagulant frequently have a prolonged baseline aPTT,²⁵ making it an unreliable marker of anticoagulant effect for intravenous unfractionated heparin therapy.

Critically ill infants and children. Arachchillage et al³⁵ found that infants (< 1 year old) treated with intravenous unfractionated heparin in an intensive care department had only a 32.4% correlation between aPTT and anti-Xa levels, which was lower than that found in children ages 1 to 15 (66%) and adults (52%). In two-thirds of cases of discordant aPTT and anti-Xa levels, the aPTT was elevated (supratherapeutic) while the anti-Xa assay was within the therapeutic range (0.3–0.7 U/mL). Despite the lack of data on clinical outcomes (eg, rates of thrombosis and bleeding) with the use of an anti-Xa assay, it has been considered the method of choice for unfractionated heparin monitoring in critically ill children, and especially in those under age 1.^{41,44,62–64}

While anti-Xa assays may also be better for unfractionated heparin monitoring in critically ill adults, the lack of clinical outcome data from large-scale randomized trials has precluded evidence-based recommendations favoring them over the aPTT.^8,34

 

 

LIMITATIONS OF ANTI-Xa ASSAYS

Anti-Xa assays are hampered by some technical limitations:

Samples must be processed within 1 hour to avoid heparin neutralization.³⁴

Samples must be clear. Hemolyzed or opaque samples (eg, due to bilirubin levels > 6.6 mg/dL or triglyceride levels > 360 mg/dL) cannot be processed, as they can cause falsely low levels.

Exposure to other anticoagulants can interfere with the results. The anti-Xa assay may be unreliable for unfractionated heparin monitoring in patients who are transitioned from low-molecular-weight heparins, fondaparinux, or an oral factor Xa inhibitor (apixaban, betrixaban, edoxaban, rivaroxaban) to intravenous unfractionated heparin, eg, due to hospitalization or acute kidney injury.^65,66 Different reports have found that anti-Xa assays may be elevated for as long as 63 to 96 hours after the last dose of oral Xa inhibitors,^67–69 potentially resulting in underdosing of unfractionated heparin. In such settings, unfractionated heparin therapy should be monitored by the aPTT.

ANTI-Xa ASSAYS AND LOW-MOLECULAR-WEIGHT HEPARINS

Most patients receiving low-molecular-weight heparins do not need laboratory monitoring.⁸ Alhenc-Gelas et al⁷⁰ randomized patients to receive dalteparin in doses either based on weight or guided by anti-Xa assay results, and found that dose adjustments were rare and lacked clinical benefit.

The suggested therapeutic anti-Xa levels for low-molecular-weight heparins are:

• 0.5–1.2 U/mL for twice-daily enoxaparin
• 1.0–2.0 U/mL for once-daily enoxaparin or dalteparin.

Levels should be measured at peak plasma level (ie, 3–4 hours after subcutaneous injection, except during pregnancy, when it is 4–6 hours), and only after at least 3 doses of low-molecular-weight heparin.^8,71 Unlike the anti-Xa therapeutic range recommended for unfractionated heparin therapy, these ranges are not based on prospective data, and if the assay result is outside the suggested therapeutic target range, current guidelines offer no advice on safely adjusting the dose.^8,71

Measuring anti-Xa activity is particularly important for pregnant women with a mechanical prosthetic heart valve who are treated with low-molecular-weight heparins. In this setting, valve thrombosis and cardioembolic events have been reported in patients with peak low-molecular-weight heparin anti-Xa assay levels below or even at the lower end of the therapeutic range, and increased bleeding risk has been reported with elevated anti-Xa levels.^71–74 Measuring trough low-molecular-weight heparin anti-Xa levels has been suggested to guide dose adjustments during pregnancy.⁷⁵

Clearance of low-molecular-weight heparins as measured by the anti-Xa assay is highly correlated with creatinine clearance.^76,77 A strong linear correlation has been demonstrated between creatine clearance and anti-Xa levels of enoxaparin after multiple therapeutic doses, and low-molecular-weight heparins accumulate in the plasma, especially in patients with creatine clearance less than 30 mL/min.⁷⁸ The risk of major bleeding is significantly increased in patients with severe renal insufficiency (creatinine clearance < 30 mL/min) not on dialysis who are treated with either prophylactic or therapeutic doses of low-molecular-weight heparin.^79–81 In a meta-analysis, the risk of bleeding with therapeutic-intensity doses of enoxaparin was 4 times higher than with prophylactic-intensity doses.⁷⁹ Although bleeding risk appears to be reduced when the enoxaparin dose is reduced by 50%,⁸ the efficacy and safety of this strategy has not been determined by prospective trials.

ANTI-Xa ASSAYS IN PATIENTS RECEIVING DIRECT ORAL ANTICOAGULANTS

Direct oral factor Xa inhibitors cannot be measured accurately by heparin anti-Xa assays. Nevertheless, such assays may be useful to assess whether clinically relevant plasma levels are present in cases of major bleeding, suspected anticoagulant failure, or patient noncompliance.⁸²

Intense research has focused on developing drug-specific chromogenic anti-Xa assays using calibrators and standards for apixaban, edoxaban, and rivaroxaban,^82,83 and good linear correlation has been shown with some assays.^82,84 In patients treated with oral factor Xa inhibitors who need to undergo an urgent invasive procedure associated with high bleeding risk, use of a specific reversal agent may be considered with drug concentrations more than 30 ng/mL measured by a drug-specific anti-Xa assay. A similar suggestion has been made for drug concentrations more than 50 ng/mL in the setting of major bleeding.⁸⁵ Unfortunately, such assays are not widely available at this time.^82,86

While drug-specific anti-Xa assays could become clinically important to guide reversal strategies, their relevance for drug monitoring remains uncertain. This is because no therapeutic target ranges have been established for any of the direct oral anticoagulants, which were approved on the basis of favorable clinical trial outcomes that neither measured nor were correlated with specific drug levels in plasma. Therefore, a specific anti-Xa level cannot yet be used as a marker of clinical efficacy for any specific oral direct Xa inhibitor.

Should clinicians abandon the activated partial thromboplastin time (aPTT) for monitoring heparin therapy in favor of tests that measure the activity of the patient’s plasma against activated factor X (anti-Xa assays)?

Although other anticoagulants are now available for preventing and treating arterial and venous thromboembolism, unfractionated heparin—which requires laboratory monitoring of therapy—is still widely used. And this monitoring can be challenging. Despite its wide use, the aPTT lacks standardization, and the role of alternative monitoring assays such as the anti-Xa assay is not well defined.

This article reviews the advantages, limitations, and clinical applicability of anti-Xa assays for monitoring therapy with unfractionated heparin and other anticoagulants.

UNFRACTIONATED HEPARIN AND WARFARIN ARE STILL WIDELY USED

Until the mid-1990s, unfractionated heparin and oral vitamin K antagonists (eg, warfarin) were the only anticoagulants widely available for clinical use. These agents have complex pharmacokinetic and pharmacodynamic properties, resulting in highly variable dosing requirements (both between patients and in individual patients) and narrow therapeutic windows, making frequent laboratory monitoring and dose adjustments mandatory.

Over the past 3 decades, other anticoagulants have been approved, including low-molecular-weight heparins, fondaparinux, parenteral direct thrombin inhibitors, and direct oral anticoagulants. While these agents have expanded the options for preventing and treating thromboembolism, unfractionated heparin and warfarin are still the most appropriate choices for many patients, eg, those with stage 4 chronic kidney disease and end-stage renal disease on dialysis, and those with mechanical heart valves.

In addition, unfractionated heparin remains the anticoagulant of choice during procedures such as hemodialysis, percutaneous transluminal angioplasty, and cardiopulmonary bypass, as well as in hospitalized and critically ill patients, who often have acute kidney injury or require frequent interruptions of therapy for invasive procedures. In these scenarios, unfractionated heparin is typically preferred because of its short plasma half-life, complete reversibility by protamine, safety regardless of renal function, and low cost compared with parenteral direct thrombin inhibitors.

As long as unfractionated heparin and warfarin remain important therapies, the need for their laboratory monitoring continues. For warfarin monitoring, the prothrombin time and international normalized ratio are validated and widely reproducible methods. But monitoring unfractionated heparin therapy remains a challenge.

UNFRACTIONATED HEPARIN’S EFFECT IS UNPREDICTABLE

Unfractionated heparin, a negatively charged mucopolysaccharide, inhibits coagulation by binding to antithrombin through the high-affinity pentasaccharide sequence.^1–6 Such binding induces a conformational change in the antithrombin molecule, converting it to a rapid inhibitor of several coagulation proteins, especially factors IIa and Xa.^2–4

Unfractionated heparin inhibits factors IIa and Xa in a 1:1 ratio, but low-molecular-weight heparins inhibit factor Xa more than factor IIa, with IIa-Xa inhibition ratios ranging from 1:2 to 1:4, owing to their smaller molecular size.⁷

One of the most important reasons for the unpredictable and highly variable individual responses to unfractionated heparin is that, infused into the blood, the large and negatively charged unfractionated heparin molecules bind nonspecifically to positively charged plasma proteins.⁷ In patients who are critically ill, have acute infections or inflammatory states, or have undergone major surgery, unfractionated heparin binds to acute-phase proteins that are elevated, particularly factor VIII. This results in fewer free heparin molecules and a variable anticoagulant effect.⁸

In contrast, low-molecular-weight heparins have longer half-lives and bind less to plasma proteins, resulting in more predictable plasma levels following subcutaneous injection.⁹

 

 

MONITORING UNFRACTIONATED HEPARIN IMPROVES OUTCOMES

In 1960, Barritt and Jordan¹⁰ conducted a small but landmark trial that established the clinical importance of unfractionated heparin for treating venous thromboembolism. None of the patients who received unfractionated heparin for acute pulmonary embolism developed a recurrence during the subsequent 2 weeks, while 50% of those who did not receive it had recurrent pulmonary embolism, fatal in half of the cases.

The importance of achieving a specific aPTT therapeutic target was not demonstrated until a 1972 study by Basu et al,¹¹ in which 162 patients with venous thromboembolism were treated with heparin with a target aPTT of 1.5 to 2.5 times the control value. Patients who suffered recurrent events had subtherapeutic aPTT values on 71% of treatment days, while the rest of the patients, with no recurrences, had subtherapeutic aPTT values only 28% of treatment days. The different outcomes could not be explained by the average daily dose of unfractionated heparin, which was similar in the patients regardless of recurrence.

Subsequent studies showed that the best outcomes occur when unfractionated heparin is given in doses high enough to rapidly achieve a therapeutic prolongation of the aPTT,^12–14 and that the total daily dose is also important in preventing recurrences.^15,16 Failure to achieve a target aPTT within 24 hours of starting unfractionated heparin is associated with increased risk of recurrent venous thromboembolism.^13,17

Raschke et al¹⁷ found that patients prospectively randomized to weight-based doses of intravenous unfractionated heparin (bolus plus infusion) achieved significantly higher rates of therapeutic aPTT within 6 hours and 24 hours after starting the infusion, and had significantly lower rates of recurrent venous thromboembolism than those randomized to a fixed unfractionated heparin protocol, without an increase in major bleeding.

Smith et al,¹⁸ in a study of 400 consecutive patients with acute pulmonary embolism treated with unfractionated heparin, found that patients who achieved a therapeutic aPTT within 24 hours had lower in-hospital and 30-day mortality rates than those who did not achieve the first therapeutic aPTT until more than 24 hours after starting unfractionated heparin infusion.

Such data lend support to the widely accepted practice and current guideline recommendation⁸ of using laboratory assays to adjust the dose of unfractionated heparin to achieve and maintain a therapeutic target. The use of dosing nomograms significantly reduces the time to achieve a therapeutic aPTT while minimizing subtherapeutic and supratherapeutic unfractionated heparin levels.^19,20

THE aPTT REFLECTS THROMBIN INHIBITION

The aPTT has a log-linear relationship with plasma concentrations of unfractionated heparin,²¹ but it was not developed specifically for monitoring unfractionated heparin therapy. Originally described in 1953 as a screening tool for hemophilia,^22–24 the aPTT is prolonged in the setting of factor deficiencies (typically with levels < 45%, except for factors VII and XIII), as well as lupus anticoagulants and therapy with parenteral direct thrombin inhibitors.^8,25,26

Because thrombin (factor IIa) is 10 times more sensitive than factor Xa to inhibition by the heparin-antithrombin complex,^4,7 thrombin inhibition appears to be the most likely mechanism by which unfractionated heparin prolongs the aPTT. In contrast, aPTT is minimally or not at all prolonged by low-molecular-weight heparins, which are predominantly factor Xa inhibitors.⁷

HEPARIN ASSAYS MEASURE UNFRACTIONATED HEPARIN ACTIVITY

While the aPTT is a surrogate marker of unfractionated heparin activity in plasma, unfractionated heparin activity can be measured more precisely by so-called heparin assays, which are typically not direct measures of the plasma concentration of heparins, but rather functional assays that provide indirect estimates. They include protamine sulfate titration assays and anti-Xa assays.

Protamine sulfate titration assays measure the amount of protamine sulfate required to neutralize heparin: the more protamine required, the greater the estimated concentration of unfractionated heparin in plasma.^8,27–29 Protamine titration assays are technically demanding, so they are rarely used clinically.

Anti-Xa assays provide a measure of the functional level of heparins in plasma.^29–33 Chromogenic anti-Xa assays are available on automated analyzers with standardized kits^29,33,34 and may be faster to perform than the aPTT.³⁵

Experiments in rabbits show that unfractionated heparin inhibits thrombus formation and extension at concentrations of 0.2 to 0.4 U/mL as measured by the protamine titration assay,²⁷ which correlated with an anti-Xa activity of 0.35 to 0.67 U/mL in a randomized controlled trial.³²

Assays that directly measure the plasma concentration of heparin exist but are not clinically relevant because they also measure heparin molecules lacking the pentasaccharide sequence, which have no anticoagulant activity.³⁶

 

 

ANTI-Xa ASSAY VS THE aPTT

Anti-Xa assays are more expensive than the aPTT and are not available in all hospitals. For these reasons, the aPTT remains the most commonly used laboratory assay for monitoring unfractionated heparin therapy.

However, the aPTT correlates poorly with the activity level of unfractionated heparin in plasma. In one study, an anti-Xa level of 0.3 U/mL corresponded to aPTT results ranging from 47 to 108 seconds.³¹ Furthermore, in studies that used a heparin therapeutic target based on an aPTT ratio 1.5 to 2.5 times the control aPTT value, the lower end of that target range was often associated with subtherapeutic plasma unfractionated heparin activity measured by anti-Xa and protamine titration assays.^28,31

Because of these limitations, individual laboratories should determine their own aPTT therapeutic target ranges for unfractionated heparin based on the response curves obtained with the reagent and coagulometer used. The optimal therapeutic aPTT range for treating acute venous thromboembolism should be defined as the aPTT range (in seconds) that correlates with a plasma activity level of unfractionated heparin of 0.3 to 0.7 U/mL based on a chromogenic anti-Xa assay, or 0.2 to 0.4 U/mL based on a protamine titration assay.^32,34–36

Nevertheless, the anticoagulant effect of unfractionated heparin as measured by the aPTT can be unpredictable and can vary widely among individuals and in the same patient.⁷ This wide variability can be explained by a number of technical and biologic variables. Different commercial aPTT reagents, different lots of the same reagent, and different reagent and instrument combinations have different sensitivities to unfractionated heparin, which can lead to variable aPTT results.³⁷ Moreover, high plasma levels of acute-phase proteins, low plasma antithrombin levels, consumptive coagulopathies, liver failure, and lupus anticoagulants may also affect the aPTT.^{7,25,32,36–41} These variables account for the poor correlation—ranging from 25% to 66%—reported between aPTT and anti-Xa assays.^32,42–48

Such discrepancies may have serious clinical implications: if a patient’s aPTT is low (subtherapeutic) or high (supratherapeutic) but the anti-Xa assay result is within the therapeutic range (0.3–0.7 units/mL), changing the dose of unfractionated heparin (guided by an aPTT nomogram) may increase the risk of bleeding or of recurrent thromboembolism.

CLINICAL APPLICABILITY OF THE ANTI-Xa ASSAY

Neither anti-Xa nor protamine titration assays are standardized across reference laboratories, but chromogenic anti-Xa assays have better interlaboratory correlation than the aPTT^49,50 and can be calibrated specifically for unfractionated or low-molecular-weight heparins.^29,33

Although reagent costs are higher for chromogenic anti-Xa assays than for the aPTT, some technical variables (described below) may partially offset the cost difference.^29,33,41 In addition, unlike the aPTT, anti-Xa assays do not need local calibration; the therapeutic range for unfractionated heparin is the same (0.3–0.7 U/mL) regardless of instrument or reagent.^33,41

Most important, studies have found that patients monitored by anti-Xa assay achieve significantly higher rates of therapeutic anticoagulation within 24 and 48 hours after starting unfractionated heparin infusion than those monitored by the aPTT. Fewer dose adjustments and repeat tests are required, which may also result in lower cost.^32,51–55

While these studies found chromogenic anti-Xa assays better for achieving laboratory end points, data regarding relevant clinical outcomes are more limited. In a retrospective, observational cohort study,⁵¹ the rate of venous thromboembolism or bleeding-related death was 2% in patients receiving unfractionated heparin therapy monitored by anti-Xa assay and 6% in patients monitored by aPTT (P = .62). Rates of major hemorrhage were also not significantly different.

In a randomized controlled trial³² in 131 patients with acute venous thromboembolism and heparin resistance, rates of recurrent venous thromboembolism were 4.6% and 6.1% in the groups randomized to anti-Xa and aPTT monitoring, respectively, whereas overall bleeding rates were 1.5% and 6.1%, respectively. Again, the differences were not statistically significant.

Heparin resistance. Some patients require unusually high doses of unfractionated heparin to achieve a therapeutic aPTT: typically, more than 35,000 U over 24 hours,^7,8,32 or total daily doses that exceed their estimated weight-based requirements. Heparin resistance has been observed in various clinical settings.^{7,8,32,37–40,59–61} Patients with heparin resistance monitored by anti-Xa had similar rates of recurrent venous thromboembolism while receiving significantly lower doses of unfractionated heparin than those monitored by the aPTT.³²

Lupus anticoagulant. Patients with the specific antiphospholipid antibody known as lupus anticoagulant frequently have a prolonged baseline aPTT,²⁵ making it an unreliable marker of anticoagulant effect for intravenous unfractionated heparin therapy.

Critically ill infants and children. Arachchillage et al³⁵ found that infants (< 1 year old) treated with intravenous unfractionated heparin in an intensive care department had only a 32.4% correlation between aPTT and anti-Xa levels, which was lower than that found in children ages 1 to 15 (66%) and adults (52%). In two-thirds of cases of discordant aPTT and anti-Xa levels, the aPTT was elevated (supratherapeutic) while the anti-Xa assay was within the therapeutic range (0.3–0.7 U/mL). Despite the lack of data on clinical outcomes (eg, rates of thrombosis and bleeding) with the use of an anti-Xa assay, it has been considered the method of choice for unfractionated heparin monitoring in critically ill children, and especially in those under age 1.^{41,44,62–64}

While anti-Xa assays may also be better for unfractionated heparin monitoring in critically ill adults, the lack of clinical outcome data from large-scale randomized trials has precluded evidence-based recommendations favoring them over the aPTT.^8,34

 

 

LIMITATIONS OF ANTI-Xa ASSAYS

Anti-Xa assays are hampered by some technical limitations:

Samples must be processed within 1 hour to avoid heparin neutralization.³⁴

Samples must be clear. Hemolyzed or opaque samples (eg, due to bilirubin levels > 6.6 mg/dL or triglyceride levels > 360 mg/dL) cannot be processed, as they can cause falsely low levels.

Exposure to other anticoagulants can interfere with the results. The anti-Xa assay may be unreliable for unfractionated heparin monitoring in patients who are transitioned from low-molecular-weight heparins, fondaparinux, or an oral factor Xa inhibitor (apixaban, betrixaban, edoxaban, rivaroxaban) to intravenous unfractionated heparin, eg, due to hospitalization or acute kidney injury.^65,66 Different reports have found that anti-Xa assays may be elevated for as long as 63 to 96 hours after the last dose of oral Xa inhibitors,^67–69 potentially resulting in underdosing of unfractionated heparin. In such settings, unfractionated heparin therapy should be monitored by the aPTT.

ANTI-Xa ASSAYS AND LOW-MOLECULAR-WEIGHT HEPARINS

Most patients receiving low-molecular-weight heparins do not need laboratory monitoring.⁸ Alhenc-Gelas et al⁷⁰ randomized patients to receive dalteparin in doses either based on weight or guided by anti-Xa assay results, and found that dose adjustments were rare and lacked clinical benefit.

The suggested therapeutic anti-Xa levels for low-molecular-weight heparins are:

• 0.5–1.2 U/mL for twice-daily enoxaparin
• 1.0–2.0 U/mL for once-daily enoxaparin or dalteparin.

Levels should be measured at peak plasma level (ie, 3–4 hours after subcutaneous injection, except during pregnancy, when it is 4–6 hours), and only after at least 3 doses of low-molecular-weight heparin.^8,71 Unlike the anti-Xa therapeutic range recommended for unfractionated heparin therapy, these ranges are not based on prospective data, and if the assay result is outside the suggested therapeutic target range, current guidelines offer no advice on safely adjusting the dose.^8,71

Measuring anti-Xa activity is particularly important for pregnant women with a mechanical prosthetic heart valve who are treated with low-molecular-weight heparins. In this setting, valve thrombosis and cardioembolic events have been reported in patients with peak low-molecular-weight heparin anti-Xa assay levels below or even at the lower end of the therapeutic range, and increased bleeding risk has been reported with elevated anti-Xa levels.^71–74 Measuring trough low-molecular-weight heparin anti-Xa levels has been suggested to guide dose adjustments during pregnancy.⁷⁵

Clearance of low-molecular-weight heparins as measured by the anti-Xa assay is highly correlated with creatinine clearance.^76,77 A strong linear correlation has been demonstrated between creatine clearance and anti-Xa levels of enoxaparin after multiple therapeutic doses, and low-molecular-weight heparins accumulate in the plasma, especially in patients with creatine clearance less than 30 mL/min.⁷⁸ The risk of major bleeding is significantly increased in patients with severe renal insufficiency (creatinine clearance < 30 mL/min) not on dialysis who are treated with either prophylactic or therapeutic doses of low-molecular-weight heparin.^79–81 In a meta-analysis, the risk of bleeding with therapeutic-intensity doses of enoxaparin was 4 times higher than with prophylactic-intensity doses.⁷⁹ Although bleeding risk appears to be reduced when the enoxaparin dose is reduced by 50%,⁸ the efficacy and safety of this strategy has not been determined by prospective trials.

ANTI-Xa ASSAYS IN PATIENTS RECEIVING DIRECT ORAL ANTICOAGULANTS

Direct oral factor Xa inhibitors cannot be measured accurately by heparin anti-Xa assays. Nevertheless, such assays may be useful to assess whether clinically relevant plasma levels are present in cases of major bleeding, suspected anticoagulant failure, or patient noncompliance.⁸²

Intense research has focused on developing drug-specific chromogenic anti-Xa assays using calibrators and standards for apixaban, edoxaban, and rivaroxaban,^82,83 and good linear correlation has been shown with some assays.^82,84 In patients treated with oral factor Xa inhibitors who need to undergo an urgent invasive procedure associated with high bleeding risk, use of a specific reversal agent may be considered with drug concentrations more than 30 ng/mL measured by a drug-specific anti-Xa assay. A similar suggestion has been made for drug concentrations more than 50 ng/mL in the setting of major bleeding.⁸⁵ Unfortunately, such assays are not widely available at this time.^82,86

While drug-specific anti-Xa assays could become clinically important to guide reversal strategies, their relevance for drug monitoring remains uncertain. This is because no therapeutic target ranges have been established for any of the direct oral anticoagulants, which were approved on the basis of favorable clinical trial outcomes that neither measured nor were correlated with specific drug levels in plasma. Therefore, a specific anti-Xa level cannot yet be used as a marker of clinical efficacy for any specific oral direct Xa inhibitor.

Should clinicians abandon the activated partial thromboplastin time (aPTT) for monitoring heparin therapy in favor of tests that measure the activity of the patient’s plasma against activated factor X (anti-Xa assays)?

Although other anticoagulants are now available for preventing and treating arterial and venous thromboembolism, unfractionated heparin—which requires laboratory monitoring of therapy—is still widely used. And this monitoring can be challenging. Despite its wide use, the aPTT lacks standardization, and the role of alternative monitoring assays such as the anti-Xa assay is not well defined.

This article reviews the advantages, limitations, and clinical applicability of anti-Xa assays for monitoring therapy with unfractionated heparin and other anticoagulants.

UNFRACTIONATED HEPARIN AND WARFARIN ARE STILL WIDELY USED

Until the mid-1990s, unfractionated heparin and oral vitamin K antagonists (eg, warfarin) were the only anticoagulants widely available for clinical use. These agents have complex pharmacokinetic and pharmacodynamic properties, resulting in highly variable dosing requirements (both between patients and in individual patients) and narrow therapeutic windows, making frequent laboratory monitoring and dose adjustments mandatory.

Over the past 3 decades, other anticoagulants have been approved, including low-molecular-weight heparins, fondaparinux, parenteral direct thrombin inhibitors, and direct oral anticoagulants. While these agents have expanded the options for preventing and treating thromboembolism, unfractionated heparin and warfarin are still the most appropriate choices for many patients, eg, those with stage 4 chronic kidney disease and end-stage renal disease on dialysis, and those with mechanical heart valves.

In addition, unfractionated heparin remains the anticoagulant of choice during procedures such as hemodialysis, percutaneous transluminal angioplasty, and cardiopulmonary bypass, as well as in hospitalized and critically ill patients, who often have acute kidney injury or require frequent interruptions of therapy for invasive procedures. In these scenarios, unfractionated heparin is typically preferred because of its short plasma half-life, complete reversibility by protamine, safety regardless of renal function, and low cost compared with parenteral direct thrombin inhibitors.

As long as unfractionated heparin and warfarin remain important therapies, the need for their laboratory monitoring continues. For warfarin monitoring, the prothrombin time and international normalized ratio are validated and widely reproducible methods. But monitoring unfractionated heparin therapy remains a challenge.

UNFRACTIONATED HEPARIN’S EFFECT IS UNPREDICTABLE

Unfractionated heparin, a negatively charged mucopolysaccharide, inhibits coagulation by binding to antithrombin through the high-affinity pentasaccharide sequence.^1–6 Such binding induces a conformational change in the antithrombin molecule, converting it to a rapid inhibitor of several coagulation proteins, especially factors IIa and Xa.^2–4

Unfractionated heparin inhibits factors IIa and Xa in a 1:1 ratio, but low-molecular-weight heparins inhibit factor Xa more than factor IIa, with IIa-Xa inhibition ratios ranging from 1:2 to 1:4, owing to their smaller molecular size.⁷

One of the most important reasons for the unpredictable and highly variable individual responses to unfractionated heparin is that, infused into the blood, the large and negatively charged unfractionated heparin molecules bind nonspecifically to positively charged plasma proteins.⁷ In patients who are critically ill, have acute infections or inflammatory states, or have undergone major surgery, unfractionated heparin binds to acute-phase proteins that are elevated, particularly factor VIII. This results in fewer free heparin molecules and a variable anticoagulant effect.⁸

In contrast, low-molecular-weight heparins have longer half-lives and bind less to plasma proteins, resulting in more predictable plasma levels following subcutaneous injection.⁹

 

 

MONITORING UNFRACTIONATED HEPARIN IMPROVES OUTCOMES

In 1960, Barritt and Jordan¹⁰ conducted a small but landmark trial that established the clinical importance of unfractionated heparin for treating venous thromboembolism. None of the patients who received unfractionated heparin for acute pulmonary embolism developed a recurrence during the subsequent 2 weeks, while 50% of those who did not receive it had recurrent pulmonary embolism, fatal in half of the cases.

The importance of achieving a specific aPTT therapeutic target was not demonstrated until a 1972 study by Basu et al,¹¹ in which 162 patients with venous thromboembolism were treated with heparin with a target aPTT of 1.5 to 2.5 times the control value. Patients who suffered recurrent events had subtherapeutic aPTT values on 71% of treatment days, while the rest of the patients, with no recurrences, had subtherapeutic aPTT values only 28% of treatment days. The different outcomes could not be explained by the average daily dose of unfractionated heparin, which was similar in the patients regardless of recurrence.

Subsequent studies showed that the best outcomes occur when unfractionated heparin is given in doses high enough to rapidly achieve a therapeutic prolongation of the aPTT,^12–14 and that the total daily dose is also important in preventing recurrences.^15,16 Failure to achieve a target aPTT within 24 hours of starting unfractionated heparin is associated with increased risk of recurrent venous thromboembolism.^13,17

Raschke et al¹⁷ found that patients prospectively randomized to weight-based doses of intravenous unfractionated heparin (bolus plus infusion) achieved significantly higher rates of therapeutic aPTT within 6 hours and 24 hours after starting the infusion, and had significantly lower rates of recurrent venous thromboembolism than those randomized to a fixed unfractionated heparin protocol, without an increase in major bleeding.

Smith et al,¹⁸ in a study of 400 consecutive patients with acute pulmonary embolism treated with unfractionated heparin, found that patients who achieved a therapeutic aPTT within 24 hours had lower in-hospital and 30-day mortality rates than those who did not achieve the first therapeutic aPTT until more than 24 hours after starting unfractionated heparin infusion.

Such data lend support to the widely accepted practice and current guideline recommendation⁸ of using laboratory assays to adjust the dose of unfractionated heparin to achieve and maintain a therapeutic target. The use of dosing nomograms significantly reduces the time to achieve a therapeutic aPTT while minimizing subtherapeutic and supratherapeutic unfractionated heparin levels.^19,20

THE aPTT REFLECTS THROMBIN INHIBITION

The aPTT has a log-linear relationship with plasma concentrations of unfractionated heparin,²¹ but it was not developed specifically for monitoring unfractionated heparin therapy. Originally described in 1953 as a screening tool for hemophilia,^22–24 the aPTT is prolonged in the setting of factor deficiencies (typically with levels < 45%, except for factors VII and XIII), as well as lupus anticoagulants and therapy with parenteral direct thrombin inhibitors.^8,25,26

Because thrombin (factor IIa) is 10 times more sensitive than factor Xa to inhibition by the heparin-antithrombin complex,^4,7 thrombin inhibition appears to be the most likely mechanism by which unfractionated heparin prolongs the aPTT. In contrast, aPTT is minimally or not at all prolonged by low-molecular-weight heparins, which are predominantly factor Xa inhibitors.⁷

HEPARIN ASSAYS MEASURE UNFRACTIONATED HEPARIN ACTIVITY

While the aPTT is a surrogate marker of unfractionated heparin activity in plasma, unfractionated heparin activity can be measured more precisely by so-called heparin assays, which are typically not direct measures of the plasma concentration of heparins, but rather functional assays that provide indirect estimates. They include protamine sulfate titration assays and anti-Xa assays.

Protamine sulfate titration assays measure the amount of protamine sulfate required to neutralize heparin: the more protamine required, the greater the estimated concentration of unfractionated heparin in plasma.^8,27–29 Protamine titration assays are technically demanding, so they are rarely used clinically.

Anti-Xa assays provide a measure of the functional level of heparins in plasma.^29–33 Chromogenic anti-Xa assays are available on automated analyzers with standardized kits^29,33,34 and may be faster to perform than the aPTT.³⁵

Experiments in rabbits show that unfractionated heparin inhibits thrombus formation and extension at concentrations of 0.2 to 0.4 U/mL as measured by the protamine titration assay,²⁷ which correlated with an anti-Xa activity of 0.35 to 0.67 U/mL in a randomized controlled trial.³²

Assays that directly measure the plasma concentration of heparin exist but are not clinically relevant because they also measure heparin molecules lacking the pentasaccharide sequence, which have no anticoagulant activity.³⁶

 

 

ANTI-Xa ASSAY VS THE aPTT

Anti-Xa assays are more expensive than the aPTT and are not available in all hospitals. For these reasons, the aPTT remains the most commonly used laboratory assay for monitoring unfractionated heparin therapy.

However, the aPTT correlates poorly with the activity level of unfractionated heparin in plasma. In one study, an anti-Xa level of 0.3 U/mL corresponded to aPTT results ranging from 47 to 108 seconds.³¹ Furthermore, in studies that used a heparin therapeutic target based on an aPTT ratio 1.5 to 2.5 times the control aPTT value, the lower end of that target range was often associated with subtherapeutic plasma unfractionated heparin activity measured by anti-Xa and protamine titration assays.^28,31

Because of these limitations, individual laboratories should determine their own aPTT therapeutic target ranges for unfractionated heparin based on the response curves obtained with the reagent and coagulometer used. The optimal therapeutic aPTT range for treating acute venous thromboembolism should be defined as the aPTT range (in seconds) that correlates with a plasma activity level of unfractionated heparin of 0.3 to 0.7 U/mL based on a chromogenic anti-Xa assay, or 0.2 to 0.4 U/mL based on a protamine titration assay.^32,34–36

Nevertheless, the anticoagulant effect of unfractionated heparin as measured by the aPTT can be unpredictable and can vary widely among individuals and in the same patient.⁷ This wide variability can be explained by a number of technical and biologic variables. Different commercial aPTT reagents, different lots of the same reagent, and different reagent and instrument combinations have different sensitivities to unfractionated heparin, which can lead to variable aPTT results.³⁷ Moreover, high plasma levels of acute-phase proteins, low plasma antithrombin levels, consumptive coagulopathies, liver failure, and lupus anticoagulants may also affect the aPTT.^{7,25,32,36–41} These variables account for the poor correlation—ranging from 25% to 66%—reported between aPTT and anti-Xa assays.^32,42–48

Such discrepancies may have serious clinical implications: if a patient’s aPTT is low (subtherapeutic) or high (supratherapeutic) but the anti-Xa assay result is within the therapeutic range (0.3–0.7 units/mL), changing the dose of unfractionated heparin (guided by an aPTT nomogram) may increase the risk of bleeding or of recurrent thromboembolism.

CLINICAL APPLICABILITY OF THE ANTI-Xa ASSAY

Neither anti-Xa nor protamine titration assays are standardized across reference laboratories, but chromogenic anti-Xa assays have better interlaboratory correlation than the aPTT^49,50 and can be calibrated specifically for unfractionated or low-molecular-weight heparins.^29,33

Although reagent costs are higher for chromogenic anti-Xa assays than for the aPTT, some technical variables (described below) may partially offset the cost difference.^29,33,41 In addition, unlike the aPTT, anti-Xa assays do not need local calibration; the therapeutic range for unfractionated heparin is the same (0.3–0.7 U/mL) regardless of instrument or reagent.^33,41

Most important, studies have found that patients monitored by anti-Xa assay achieve significantly higher rates of therapeutic anticoagulation within 24 and 48 hours after starting unfractionated heparin infusion than those monitored by the aPTT. Fewer dose adjustments and repeat tests are required, which may also result in lower cost.^32,51–55

While these studies found chromogenic anti-Xa assays better for achieving laboratory end points, data regarding relevant clinical outcomes are more limited. In a retrospective, observational cohort study,⁵¹ the rate of venous thromboembolism or bleeding-related death was 2% in patients receiving unfractionated heparin therapy monitored by anti-Xa assay and 6% in patients monitored by aPTT (P = .62). Rates of major hemorrhage were also not significantly different.

In a randomized controlled trial³² in 131 patients with acute venous thromboembolism and heparin resistance, rates of recurrent venous thromboembolism were 4.6% and 6.1% in the groups randomized to anti-Xa and aPTT monitoring, respectively, whereas overall bleeding rates were 1.5% and 6.1%, respectively. Again, the differences were not statistically significant.

Heparin resistance. Some patients require unusually high doses of unfractionated heparin to achieve a therapeutic aPTT: typically, more than 35,000 U over 24 hours,^7,8,32 or total daily doses that exceed their estimated weight-based requirements. Heparin resistance has been observed in various clinical settings.^{7,8,32,37–40,59–61} Patients with heparin resistance monitored by anti-Xa had similar rates of recurrent venous thromboembolism while receiving significantly lower doses of unfractionated heparin than those monitored by the aPTT.³²

Lupus anticoagulant. Patients with the specific antiphospholipid antibody known as lupus anticoagulant frequently have a prolonged baseline aPTT,²⁵ making it an unreliable marker of anticoagulant effect for intravenous unfractionated heparin therapy.

Critically ill infants and children. Arachchillage et al³⁵ found that infants (< 1 year old) treated with intravenous unfractionated heparin in an intensive care department had only a 32.4% correlation between aPTT and anti-Xa levels, which was lower than that found in children ages 1 to 15 (66%) and adults (52%). In two-thirds of cases of discordant aPTT and anti-Xa levels, the aPTT was elevated (supratherapeutic) while the anti-Xa assay was within the therapeutic range (0.3–0.7 U/mL). Despite the lack of data on clinical outcomes (eg, rates of thrombosis and bleeding) with the use of an anti-Xa assay, it has been considered the method of choice for unfractionated heparin monitoring in critically ill children, and especially in those under age 1.^{41,44,62–64}

While anti-Xa assays may also be better for unfractionated heparin monitoring in critically ill adults, the lack of clinical outcome data from large-scale randomized trials has precluded evidence-based recommendations favoring them over the aPTT.^8,34

 

 

LIMITATIONS OF ANTI-Xa ASSAYS

Anti-Xa assays are hampered by some technical limitations:

Samples must be processed within 1 hour to avoid heparin neutralization.³⁴

Samples must be clear. Hemolyzed or opaque samples (eg, due to bilirubin levels > 6.6 mg/dL or triglyceride levels > 360 mg/dL) cannot be processed, as they can cause falsely low levels.

Exposure to other anticoagulants can interfere with the results. The anti-Xa assay may be unreliable for unfractionated heparin monitoring in patients who are transitioned from low-molecular-weight heparins, fondaparinux, or an oral factor Xa inhibitor (apixaban, betrixaban, edoxaban, rivaroxaban) to intravenous unfractionated heparin, eg, due to hospitalization or acute kidney injury.^65,66 Different reports have found that anti-Xa assays may be elevated for as long as 63 to 96 hours after the last dose of oral Xa inhibitors,^67–69 potentially resulting in underdosing of unfractionated heparin. In such settings, unfractionated heparin therapy should be monitored by the aPTT.

ANTI-Xa ASSAYS AND LOW-MOLECULAR-WEIGHT HEPARINS

Most patients receiving low-molecular-weight heparins do not need laboratory monitoring.⁸ Alhenc-Gelas et al⁷⁰ randomized patients to receive dalteparin in doses either based on weight or guided by anti-Xa assay results, and found that dose adjustments were rare and lacked clinical benefit.

The suggested therapeutic anti-Xa levels for low-molecular-weight heparins are:

• 0.5–1.2 U/mL for twice-daily enoxaparin
• 1.0–2.0 U/mL for once-daily enoxaparin or dalteparin.

Levels should be measured at peak plasma level (ie, 3–4 hours after subcutaneous injection, except during pregnancy, when it is 4–6 hours), and only after at least 3 doses of low-molecular-weight heparin.^8,71 Unlike the anti-Xa therapeutic range recommended for unfractionated heparin therapy, these ranges are not based on prospective data, and if the assay result is outside the suggested therapeutic target range, current guidelines offer no advice on safely adjusting the dose.^8,71

Measuring anti-Xa activity is particularly important for pregnant women with a mechanical prosthetic heart valve who are treated with low-molecular-weight heparins. In this setting, valve thrombosis and cardioembolic events have been reported in patients with peak low-molecular-weight heparin anti-Xa assay levels below or even at the lower end of the therapeutic range, and increased bleeding risk has been reported with elevated anti-Xa levels.^71–74 Measuring trough low-molecular-weight heparin anti-Xa levels has been suggested to guide dose adjustments during pregnancy.⁷⁵

Clearance of low-molecular-weight heparins as measured by the anti-Xa assay is highly correlated with creatinine clearance.^76,77 A strong linear correlation has been demonstrated between creatine clearance and anti-Xa levels of enoxaparin after multiple therapeutic doses, and low-molecular-weight heparins accumulate in the plasma, especially in patients with creatine clearance less than 30 mL/min.⁷⁸ The risk of major bleeding is significantly increased in patients with severe renal insufficiency (creatinine clearance < 30 mL/min) not on dialysis who are treated with either prophylactic or therapeutic doses of low-molecular-weight heparin.^79–81 In a meta-analysis, the risk of bleeding with therapeutic-intensity doses of enoxaparin was 4 times higher than with prophylactic-intensity doses.⁷⁹ Although bleeding risk appears to be reduced when the enoxaparin dose is reduced by 50%,⁸ the efficacy and safety of this strategy has not been determined by prospective trials.

ANTI-Xa ASSAYS IN PATIENTS RECEIVING DIRECT ORAL ANTICOAGULANTS

Direct oral factor Xa inhibitors cannot be measured accurately by heparin anti-Xa assays. Nevertheless, such assays may be useful to assess whether clinically relevant plasma levels are present in cases of major bleeding, suspected anticoagulant failure, or patient noncompliance.⁸²

Intense research has focused on developing drug-specific chromogenic anti-Xa assays using calibrators and standards for apixaban, edoxaban, and rivaroxaban,^82,83 and good linear correlation has been shown with some assays.^82,84 In patients treated with oral factor Xa inhibitors who need to undergo an urgent invasive procedure associated with high bleeding risk, use of a specific reversal agent may be considered with drug concentrations more than 30 ng/mL measured by a drug-specific anti-Xa assay. A similar suggestion has been made for drug concentrations more than 50 ng/mL in the setting of major bleeding.⁸⁵ Unfortunately, such assays are not widely available at this time.^82,86

While drug-specific anti-Xa assays could become clinically important to guide reversal strategies, their relevance for drug monitoring remains uncertain. This is because no therapeutic target ranges have been established for any of the direct oral anticoagulants, which were approved on the basis of favorable clinical trial outcomes that neither measured nor were correlated with specific drug levels in plasma. Therefore, a specific anti-Xa level cannot yet be used as a marker of clinical efficacy for any specific oral direct Xa inhibitor.

A 69-year-old woman was admitted to the hospital with double vision, weakness in the lower extremities, sensory loss, pain, and falls. Her symptoms started with sudden onset of horizontal diplopia 6 weeks before, followed by gradually worsening lower-extremity weakness, as well as ataxia and patchy and bilateral radicular burning leg pain more pronounced on the right. Her medical history included narcolepsy, obstructive sleep apnea, hypertension, hyperlipidemia, and bilateral knee replacements for osteoarthritis.

Neurologic examination showed inability to abduct the right eye, bilateral hip flexion weakness, decreased pinprick response, decreased proprioception, and diminished muscle stretch reflexes in the lower extremities. Magnetic resonance imaging (MRI) of the brain without contrast and magnetic resonance angiography of the brain and carotid arteries showed no evidence of acute stroke. No abnormalities were noted on electrocardiography and echocardiography.

A diagnosis of idiopathic peripheral neuropathy was made, and outpatient physical therapy was recommended. Over the subsequent 2 weeks, her condition declined to the point where she needed a walker. She continued to have worsening leg weakness with falls, prompting hospital readmission.

INITIAL EVALUATION

In addition to her diplopia and weakness, she said she had lost 15 pounds since the onset of symptoms and had experienced symptoms suggesting urinary retention.

Physical examination

Her temperature was 37°C (98.6°F), heart rate 79 beats per minute, blood pressure 117/86 mm Hg, respiratory rate 14 breaths per minute, and oxygen saturation 98% on room air. Examination of the head, neck, heart, lung, abdomen, lymph nodes, and extremities yielded nothing remarkable except for chronic venous changes in the lower extremities.

The neurologic examination showed incomplete lateral gaze bilaterally (cranial nerve VI dysfunction). Strength in the upper extremities was normal. In the legs, the Medical Research Council scale score for proximal muscle strength was 2 to 3 out of 5, and for distal muscles 3 to 4 out of 5, with the right side worse than the left and flexors and extensors affected equally. Muscle stretch reflexes were absent in both lower extremities and the left upper extremity, but intact in the right upper extremity. No abnormal corticospinal tract reflexes were elicited.

Sensory testing revealed diminished pin-prick perception in a length-dependent fashion in the lower extremities, reduced 50% compared with the hands. Gait could not be assessed due to weakness.

Initial laboratory testing

Results of initial laboratory tests—complete blood cell count, complete metabolic panel, erythrocyte sedimentation rate, C-reactive protein, thyroid-stimulating hormone, and hemoglobin A_1c—were unremarkable.

 

 

FURTHER EVALUATION AND DIFFERENTIAL DIAGNOSIS

1. Which of the following is the most likely diagnosis at this point?

• Cerebral infarction
• Guillain-Barré syndrome
• Progressive polyneuropathy
• Transverse myelitis
• Polyradiculopathy

In the absence of definitive diagnostic tests, all of the above options were considered in the differential diagnosis for this patient.

Cerebral infarction

Although acute-onset diplopia can be explained by brainstem stroke involving cranial nerve nuclei or their projections, the onset of diplopia with progressive bilateral lower-extremity weakness makes stroke unlikely. Flaccid paralysis, areflexia of the lower extremities, and sensory involvement can also be caused by acute anterior spinal artery occlusion leading to spinal cord infarction; however, the deficits are usually maximal at onset.

Guillain-Barré syndrome

The combination of acute-subacute progressive ascending weakness, sensory involvement, and diminished or absent reflexes is typical of Guillain-Barré syndrome. Cranial nerve involvement can overlap with the more typical features of the syndrome. However, most patients reach the nadir of their disease by 4 weeks after initial symptom onset, even without treatment.¹ This patient’s condition continued to worsen over 8 weeks. In addition, the asymmetric lower-extremity weakness and sparing of the arms are atypical for Guillain-Barré syndrome.

Given the progression of symptoms, chronic inflammatory demyelinating polyneuropathy is also a consideration, typically presenting as a relapsing or progressive neuropathy in proximal and distal muscles and worsening over at least an 8-week period.²

The initial workup for Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy includes lumbar puncture to assess for albuminocytologic dissociation (elevated protein with normal white blood cell count) in cerebrospinal fluid (CSF), and electromyography (EMG) to assess for neuro­physiologic evidence of peripheral nerve demyelination. In Miller-Fisher syndrome, a rare variant of Guillain-Barré syndrome characterized by ataxia, ophthalmoparesis, and areflexia, serum ganglioside antibodies to GQ1b are found in over 90% of patients.^3,4 Although MRI of the spine is not necessary to diagnose Guillain-Barré syndrome, it is often done to exclude other causes of lower-extremity weakness such as spinal cord or cauda equina compression that would require urgent neurosurgical consultation. MRI can support the diagnosis of Guillain-Barré syndrome when it reveals enhancement of the spinal nerve roots or cauda equina.

Other polyneuropathies

Polyneuropathy is caused by a variety of diseases that affect the function of peripheral motor, sensory, or autonomic nerves. The differential diagnosis is broad and involves inflammatory diseases (including autoimmune and paraneoplastic causes), hereditary disorders, infection, toxicity, and ischemic and nutritional deficiencies.⁵ Polyneuropathy can present in a distal-predominant, generalized, or asymmetric pattern involving individual nerve trunks termed “mononeuropathy multiplex,” as in our patient’s presentation. The initial workup includes EMG and a battery of serologic tests. In cases of severe and progressive polyneuropathy, nerve biopsy can assess for the presence of vasculitis, amyloidosis, and paraprotein deposition.

Transverse myelitis

Transverse myelitis is an inflammatory myelopathy that usually presents with acute or subacute weakness of the upper extremities or lower extremities, or both, corresponding to the level of the lesion, hyperreflexia, bladder and bowel dysfunction, spinal level of sensory loss, and autonomic involvement.⁶ The differential diagnosis of acute myelopathy includes:

• Infection (eg, herpes simplex virus, West Nile virus, Lyme disease, Mycoplasma pneumoniae, human immunodeficiency virus)
• Systemic inflammatory disease (systemic lupus erythematosus, sarcoidosis, Sjögren syndrome, scleroderma, paraneoplastic syndrome)
• Central nervous system demyelinating disease (acute disseminated encephalomyelitis, multiple sclerosis, neuromyelitis optica)
• Vascular malformation (dural arteriovenous fistula)
• Compression due to tumor, bleeding, disc herniation, infection, or abscess.

The workup involves laboratory tests to exclude systemic inflammatory and infectious causes, as well as MRI of the spine with and without contrast to identify a causative lesion. Lumbar puncture and CSF analysis may show pleocytosis, elevated protein concentration, and increased intrathecal immunoglobulin G (IgG) index.⁷

Although our patient’s presentation with subacute lower-extremity weakness, sensory changes, and bladder dysfunction were consistent with transverse myelitis, her cranial nerve abnormalities would be atypical for it.

Polyradiculopathy


Polyradiculopathy has many possible causes. In the United States, the most common causes are lumbar spondylosis, lumbar canal stenosis, and diabetic polyradiculoneuropathy.

When multiple spinal segments are affected, leptomeningeal disease involving the arachnoid and pia mater should be considered. Causes include malignant invasion, inflammatory cell accumulation, and protein deposition, leading to patchy but widespread dysfunction of spinal nerve roots and cranial nerves. Specific causes are myriad and include carcinomatous meningitis,⁸ syphilis, tuberculosis, sarcoidosis, and paraproteinemias. CSF and MRI changes are often nonspecific, leading to the need for meningeal biopsy for diagnosis.

 

 

CASE CONTINUED

During her hospitalization, our patient developed acute right upper and lower facial weakness consistent with peripheral facial mononeuropathy. Bilateral lower-extremity weakness progressed to disabling paraparesis.

She underwent lumbar puncture and CSF analysis (Table 1). The most notable findings were significant pleocytosis (72% lymphocytic predominance), protein elevation, and elevated IgG index (indicative of elevated intrathecal immunoglobulin synthesis in the central nervous system). Viral, bacterial, and fungal studies were negative. Guillain-Barré syndrome, other polyneuropathies, and spinal cord infarction would not be expected with these CSF features.

Surface EMG demonstrated normal sensory responses, and needle EMG showed chronic and active motor axon loss in the L3 and S1 root distributions, suggesting polyradiculopathy without polyneuropathy. These findings would not be expected in typical acute transverse myelitis but could be seen with spinal cord infarction.

MRI of the entire spine with and without contrast showed cauda equina nerve root thickening and enhancement, especially involving the L5 and S1 roots (Figure 1). The spinal cord appeared normal. These findings further supported polyradiculopathy and a leptomeningeal process.

Further evaluation included chest radiography, erythrocyte sedimentation rate, C-reactive protein, hemoglobin A_1c, human immunodeficiency virus testing, antinuclear antibody, antineutrophil cytoplasmic antibody, extractable nuclear antibody, GQ1b antibody, serum and CSF paraneoplastic panels, levels of vitamin B₁, B₁₂, and B₆, copper, and ceruloplasmin, and a screen for heavy metals. All results were within normal ranges.

ESTABLISHING THE DIAGNOSIS

Serum monoclonal protein analysis with immunofixation revealed IgM kappa monoclonal gammopathy with an IgM level of 1,570 (reference range 53–334 mg/dL) and M-spike 0.75 (0.00 mg/dL), serum free kappa light chains 61.1 (3.30–19.40 mg/L), lambda 9.3 (5.7–26.3 mg/L), and kappa-lambda ratio 6.57 (0.26–1.65).

2. Which is the best next step in this patient’s neurologic evaluation?

• Test CSF angiotensin-converting enzyme level
• CSF cytology
• Meningeal biopsy
• Peripheral nerve biopsy

Given the high suspicion for malignancy, CSF cytology was performed and showed increased numbers of mononuclear chronic inflammatory cells, including a mixture of lymphocytes and monocytes, favoring a reactive lymphoid pleocytosis. Flow cytometry indicated the presence of a monoclonal, CD5- and CD10- negative, B-cell lymphoproliferative disorder. The immunophenotypic findings were not specific for a single diagnosis. The differential diagnosis included marginal zone lymphoma and lymphoplasmacytic lymphoma.

3. Given the presence of serum IgM monoclonal gammopathy in this patient, which is the most likely diagnosis?

• Neurosarcoidosis
• Multiple myeloma
• Waldenström macroglobulinemia
• Carcinomatous meningitis

Study of bone marrow biopsy demonstrated limited bone marrow involvement (1%) by a lymphoproliferative disorder with plasmacytoid features, and DNA testing detected an MYD88 L265P mutation, reported to be present in 90% of patients with Waldenström macroglobulinemia.⁹ This finding confirmed the diagnosis of Waldenström macroglobulinemia with central nervous system involvement. Our patient began therapy with rituximab and methotrexate, which resulted in some improvement in strength, gait, and vision.

 

 

WALDENSTRÖM MACROGLOBULINEMIA AND BING-NEEL SYNDROME

Waldenström macroglobulinemia is a lympho­plasmacytic lymphoma associated with a monoclonal IgM protein.¹⁰ It is considered a paraproteinemic disorder, similar to multiple myeloma. The presenting symptoms and complications are related to direct tumor infiltration, hyperviscosity syndrome, and deposition of IgM in various tissues.^11,12

Waldenström macroglobulinemia is usually indolent, and treatment is reserved for patients with symptoms.^13,14 It includes rituximab, usually in combination with chemotherapy or other targeted agents.^15,16

Paraneoplastic antibody-mediated polyneuropathy may occur in these patients. However, the pattern is usually symmetrical clinically, with demyelination on EMG, and is not associated with cranial nerve or meningeal involvement. Management with plasmapheresis, corticosteroids, and intravenous immunoglobulin has not been shown to be effective.¹⁷

Involvement of the central nervous system as a complication of Waldenström macroglobulinemia has been described as Bing-Neel syndrome. It can present as diffuse malignant cell infiltration of the leptomeningeal space, white matter, or spinal cord, or in a tumoral form presenting as intraparenchymal masses or nodular lesions. The distinction between the tumoral and diffuse forms is based primarily on imaging findings.¹⁸

In a report of 44 patients with Bing-Neel syndrome, 36% presented with the disorder as the initial manifestation of Waldenström macroglobulinemia.¹⁸ The primary presenting symptoms were imbalance and gait difficulty (48%) and cranial nerve involvement (36%), which presented as predominantly facial or oculomotor nerve palsy. Cauda equina syndrome with motor involvement (seen in our patient) occurred in 14% of patients. Other presenting symptoms included cognitive impairment, sensory deficits, headache, dysarthria, aphasia, and seizures.

LEARNING POINTS

The differential diagnosis for patients presenting with multifocal neurologic symptoms can be broad, and a systematic approach to the diagnosis is necessary. Localizing the lesion is important in determining the diagnosis for patients presenting with neurologic symptoms. The process of localization begins with taking the history, is further refined during the examination, and is confirmed with diagnostic studies. Atypical presentations of relatively common neurologic diseases such as Guillain-Barré syndrome, transverse myelitis, and peripheral polyneuropathy do occur, but uncommon diagnoses need to be considered when support for the initial diagnosis is lacking.

A 69-year-old woman was admitted to the hospital with double vision, weakness in the lower extremities, sensory loss, pain, and falls. Her symptoms started with sudden onset of horizontal diplopia 6 weeks before, followed by gradually worsening lower-extremity weakness, as well as ataxia and patchy and bilateral radicular burning leg pain more pronounced on the right. Her medical history included narcolepsy, obstructive sleep apnea, hypertension, hyperlipidemia, and bilateral knee replacements for osteoarthritis.

Neurologic examination showed inability to abduct the right eye, bilateral hip flexion weakness, decreased pinprick response, decreased proprioception, and diminished muscle stretch reflexes in the lower extremities. Magnetic resonance imaging (MRI) of the brain without contrast and magnetic resonance angiography of the brain and carotid arteries showed no evidence of acute stroke. No abnormalities were noted on electrocardiography and echocardiography.

A diagnosis of idiopathic peripheral neuropathy was made, and outpatient physical therapy was recommended. Over the subsequent 2 weeks, her condition declined to the point where she needed a walker. She continued to have worsening leg weakness with falls, prompting hospital readmission.

INITIAL EVALUATION

In addition to her diplopia and weakness, she said she had lost 15 pounds since the onset of symptoms and had experienced symptoms suggesting urinary retention.

Physical examination

Her temperature was 37°C (98.6°F), heart rate 79 beats per minute, blood pressure 117/86 mm Hg, respiratory rate 14 breaths per minute, and oxygen saturation 98% on room air. Examination of the head, neck, heart, lung, abdomen, lymph nodes, and extremities yielded nothing remarkable except for chronic venous changes in the lower extremities.

The neurologic examination showed incomplete lateral gaze bilaterally (cranial nerve VI dysfunction). Strength in the upper extremities was normal. In the legs, the Medical Research Council scale score for proximal muscle strength was 2 to 3 out of 5, and for distal muscles 3 to 4 out of 5, with the right side worse than the left and flexors and extensors affected equally. Muscle stretch reflexes were absent in both lower extremities and the left upper extremity, but intact in the right upper extremity. No abnormal corticospinal tract reflexes were elicited.

Sensory testing revealed diminished pin-prick perception in a length-dependent fashion in the lower extremities, reduced 50% compared with the hands. Gait could not be assessed due to weakness.

Initial laboratory testing

Results of initial laboratory tests—complete blood cell count, complete metabolic panel, erythrocyte sedimentation rate, C-reactive protein, thyroid-stimulating hormone, and hemoglobin A_1c—were unremarkable.

 

 

FURTHER EVALUATION AND DIFFERENTIAL DIAGNOSIS

1. Which of the following is the most likely diagnosis at this point?

• Cerebral infarction
• Guillain-Barré syndrome
• Progressive polyneuropathy
• Transverse myelitis
• Polyradiculopathy

In the absence of definitive diagnostic tests, all of the above options were considered in the differential diagnosis for this patient.

Cerebral infarction

Although acute-onset diplopia can be explained by brainstem stroke involving cranial nerve nuclei or their projections, the onset of diplopia with progressive bilateral lower-extremity weakness makes stroke unlikely. Flaccid paralysis, areflexia of the lower extremities, and sensory involvement can also be caused by acute anterior spinal artery occlusion leading to spinal cord infarction; however, the deficits are usually maximal at onset.

Guillain-Barré syndrome

The combination of acute-subacute progressive ascending weakness, sensory involvement, and diminished or absent reflexes is typical of Guillain-Barré syndrome. Cranial nerve involvement can overlap with the more typical features of the syndrome. However, most patients reach the nadir of their disease by 4 weeks after initial symptom onset, even without treatment.¹ This patient’s condition continued to worsen over 8 weeks. In addition, the asymmetric lower-extremity weakness and sparing of the arms are atypical for Guillain-Barré syndrome.

Given the progression of symptoms, chronic inflammatory demyelinating polyneuropathy is also a consideration, typically presenting as a relapsing or progressive neuropathy in proximal and distal muscles and worsening over at least an 8-week period.²

The initial workup for Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy includes lumbar puncture to assess for albuminocytologic dissociation (elevated protein with normal white blood cell count) in cerebrospinal fluid (CSF), and electromyography (EMG) to assess for neuro­physiologic evidence of peripheral nerve demyelination. In Miller-Fisher syndrome, a rare variant of Guillain-Barré syndrome characterized by ataxia, ophthalmoparesis, and areflexia, serum ganglioside antibodies to GQ1b are found in over 90% of patients.^3,4 Although MRI of the spine is not necessary to diagnose Guillain-Barré syndrome, it is often done to exclude other causes of lower-extremity weakness such as spinal cord or cauda equina compression that would require urgent neurosurgical consultation. MRI can support the diagnosis of Guillain-Barré syndrome when it reveals enhancement of the spinal nerve roots or cauda equina.

Other polyneuropathies

Polyneuropathy is caused by a variety of diseases that affect the function of peripheral motor, sensory, or autonomic nerves. The differential diagnosis is broad and involves inflammatory diseases (including autoimmune and paraneoplastic causes), hereditary disorders, infection, toxicity, and ischemic and nutritional deficiencies.⁵ Polyneuropathy can present in a distal-predominant, generalized, or asymmetric pattern involving individual nerve trunks termed “mononeuropathy multiplex,” as in our patient’s presentation. The initial workup includes EMG and a battery of serologic tests. In cases of severe and progressive polyneuropathy, nerve biopsy can assess for the presence of vasculitis, amyloidosis, and paraprotein deposition.

Transverse myelitis

Transverse myelitis is an inflammatory myelopathy that usually presents with acute or subacute weakness of the upper extremities or lower extremities, or both, corresponding to the level of the lesion, hyperreflexia, bladder and bowel dysfunction, spinal level of sensory loss, and autonomic involvement.⁶ The differential diagnosis of acute myelopathy includes:

• Infection (eg, herpes simplex virus, West Nile virus, Lyme disease, Mycoplasma pneumoniae, human immunodeficiency virus)
• Systemic inflammatory disease (systemic lupus erythematosus, sarcoidosis, Sjögren syndrome, scleroderma, paraneoplastic syndrome)
• Central nervous system demyelinating disease (acute disseminated encephalomyelitis, multiple sclerosis, neuromyelitis optica)
• Vascular malformation (dural arteriovenous fistula)
• Compression due to tumor, bleeding, disc herniation, infection, or abscess.

The workup involves laboratory tests to exclude systemic inflammatory and infectious causes, as well as MRI of the spine with and without contrast to identify a causative lesion. Lumbar puncture and CSF analysis may show pleocytosis, elevated protein concentration, and increased intrathecal immunoglobulin G (IgG) index.⁷

Although our patient’s presentation with subacute lower-extremity weakness, sensory changes, and bladder dysfunction were consistent with transverse myelitis, her cranial nerve abnormalities would be atypical for it.

Polyradiculopathy


Polyradiculopathy has many possible causes. In the United States, the most common causes are lumbar spondylosis, lumbar canal stenosis, and diabetic polyradiculoneuropathy.

When multiple spinal segments are affected, leptomeningeal disease involving the arachnoid and pia mater should be considered. Causes include malignant invasion, inflammatory cell accumulation, and protein deposition, leading to patchy but widespread dysfunction of spinal nerve roots and cranial nerves. Specific causes are myriad and include carcinomatous meningitis,⁸ syphilis, tuberculosis, sarcoidosis, and paraproteinemias. CSF and MRI changes are often nonspecific, leading to the need for meningeal biopsy for diagnosis.

 

 

CASE CONTINUED

During her hospitalization, our patient developed acute right upper and lower facial weakness consistent with peripheral facial mononeuropathy. Bilateral lower-extremity weakness progressed to disabling paraparesis.

She underwent lumbar puncture and CSF analysis (Table 1). The most notable findings were significant pleocytosis (72% lymphocytic predominance), protein elevation, and elevated IgG index (indicative of elevated intrathecal immunoglobulin synthesis in the central nervous system). Viral, bacterial, and fungal studies were negative. Guillain-Barré syndrome, other polyneuropathies, and spinal cord infarction would not be expected with these CSF features.

Surface EMG demonstrated normal sensory responses, and needle EMG showed chronic and active motor axon loss in the L3 and S1 root distributions, suggesting polyradiculopathy without polyneuropathy. These findings would not be expected in typical acute transverse myelitis but could be seen with spinal cord infarction.

MRI of the entire spine with and without contrast showed cauda equina nerve root thickening and enhancement, especially involving the L5 and S1 roots (Figure 1). The spinal cord appeared normal. These findings further supported polyradiculopathy and a leptomeningeal process.

Further evaluation included chest radiography, erythrocyte sedimentation rate, C-reactive protein, hemoglobin A_1c, human immunodeficiency virus testing, antinuclear antibody, antineutrophil cytoplasmic antibody, extractable nuclear antibody, GQ1b antibody, serum and CSF paraneoplastic panels, levels of vitamin B₁, B₁₂, and B₆, copper, and ceruloplasmin, and a screen for heavy metals. All results were within normal ranges.

ESTABLISHING THE DIAGNOSIS

Serum monoclonal protein analysis with immunofixation revealed IgM kappa monoclonal gammopathy with an IgM level of 1,570 (reference range 53–334 mg/dL) and M-spike 0.75 (0.00 mg/dL), serum free kappa light chains 61.1 (3.30–19.40 mg/L), lambda 9.3 (5.7–26.3 mg/L), and kappa-lambda ratio 6.57 (0.26–1.65).

2. Which is the best next step in this patient’s neurologic evaluation?

• Test CSF angiotensin-converting enzyme level
• CSF cytology
• Meningeal biopsy
• Peripheral nerve biopsy

Given the high suspicion for malignancy, CSF cytology was performed and showed increased numbers of mononuclear chronic inflammatory cells, including a mixture of lymphocytes and monocytes, favoring a reactive lymphoid pleocytosis. Flow cytometry indicated the presence of a monoclonal, CD5- and CD10- negative, B-cell lymphoproliferative disorder. The immunophenotypic findings were not specific for a single diagnosis. The differential diagnosis included marginal zone lymphoma and lymphoplasmacytic lymphoma.

3. Given the presence of serum IgM monoclonal gammopathy in this patient, which is the most likely diagnosis?

• Neurosarcoidosis
• Multiple myeloma
• Waldenström macroglobulinemia
• Carcinomatous meningitis

Study of bone marrow biopsy demonstrated limited bone marrow involvement (1%) by a lymphoproliferative disorder with plasmacytoid features, and DNA testing detected an MYD88 L265P mutation, reported to be present in 90% of patients with Waldenström macroglobulinemia.⁹ This finding confirmed the diagnosis of Waldenström macroglobulinemia with central nervous system involvement. Our patient began therapy with rituximab and methotrexate, which resulted in some improvement in strength, gait, and vision.

 

 

WALDENSTRÖM MACROGLOBULINEMIA AND BING-NEEL SYNDROME

Waldenström macroglobulinemia is a lympho­plasmacytic lymphoma associated with a monoclonal IgM protein.¹⁰ It is considered a paraproteinemic disorder, similar to multiple myeloma. The presenting symptoms and complications are related to direct tumor infiltration, hyperviscosity syndrome, and deposition of IgM in various tissues.^11,12

Waldenström macroglobulinemia is usually indolent, and treatment is reserved for patients with symptoms.^13,14 It includes rituximab, usually in combination with chemotherapy or other targeted agents.^15,16

Paraneoplastic antibody-mediated polyneuropathy may occur in these patients. However, the pattern is usually symmetrical clinically, with demyelination on EMG, and is not associated with cranial nerve or meningeal involvement. Management with plasmapheresis, corticosteroids, and intravenous immunoglobulin has not been shown to be effective.¹⁷

Involvement of the central nervous system as a complication of Waldenström macroglobulinemia has been described as Bing-Neel syndrome. It can present as diffuse malignant cell infiltration of the leptomeningeal space, white matter, or spinal cord, or in a tumoral form presenting as intraparenchymal masses or nodular lesions. The distinction between the tumoral and diffuse forms is based primarily on imaging findings.¹⁸

In a report of 44 patients with Bing-Neel syndrome, 36% presented with the disorder as the initial manifestation of Waldenström macroglobulinemia.¹⁸ The primary presenting symptoms were imbalance and gait difficulty (48%) and cranial nerve involvement (36%), which presented as predominantly facial or oculomotor nerve palsy. Cauda equina syndrome with motor involvement (seen in our patient) occurred in 14% of patients. Other presenting symptoms included cognitive impairment, sensory deficits, headache, dysarthria, aphasia, and seizures.

LEARNING POINTS

The differential diagnosis for patients presenting with multifocal neurologic symptoms can be broad, and a systematic approach to the diagnosis is necessary. Localizing the lesion is important in determining the diagnosis for patients presenting with neurologic symptoms. The process of localization begins with taking the history, is further refined during the examination, and is confirmed with diagnostic studies. Atypical presentations of relatively common neurologic diseases such as Guillain-Barré syndrome, transverse myelitis, and peripheral polyneuropathy do occur, but uncommon diagnoses need to be considered when support for the initial diagnosis is lacking.

A 69-year-old woman was admitted to the hospital with double vision, weakness in the lower extremities, sensory loss, pain, and falls. Her symptoms started with sudden onset of horizontal diplopia 6 weeks before, followed by gradually worsening lower-extremity weakness, as well as ataxia and patchy and bilateral radicular burning leg pain more pronounced on the right. Her medical history included narcolepsy, obstructive sleep apnea, hypertension, hyperlipidemia, and bilateral knee replacements for osteoarthritis.

Neurologic examination showed inability to abduct the right eye, bilateral hip flexion weakness, decreased pinprick response, decreased proprioception, and diminished muscle stretch reflexes in the lower extremities. Magnetic resonance imaging (MRI) of the brain without contrast and magnetic resonance angiography of the brain and carotid arteries showed no evidence of acute stroke. No abnormalities were noted on electrocardiography and echocardiography.

A diagnosis of idiopathic peripheral neuropathy was made, and outpatient physical therapy was recommended. Over the subsequent 2 weeks, her condition declined to the point where she needed a walker. She continued to have worsening leg weakness with falls, prompting hospital readmission.

INITIAL EVALUATION

In addition to her diplopia and weakness, she said she had lost 15 pounds since the onset of symptoms and had experienced symptoms suggesting urinary retention.

Physical examination

Her temperature was 37°C (98.6°F), heart rate 79 beats per minute, blood pressure 117/86 mm Hg, respiratory rate 14 breaths per minute, and oxygen saturation 98% on room air. Examination of the head, neck, heart, lung, abdomen, lymph nodes, and extremities yielded nothing remarkable except for chronic venous changes in the lower extremities.

The neurologic examination showed incomplete lateral gaze bilaterally (cranial nerve VI dysfunction). Strength in the upper extremities was normal. In the legs, the Medical Research Council scale score for proximal muscle strength was 2 to 3 out of 5, and for distal muscles 3 to 4 out of 5, with the right side worse than the left and flexors and extensors affected equally. Muscle stretch reflexes were absent in both lower extremities and the left upper extremity, but intact in the right upper extremity. No abnormal corticospinal tract reflexes were elicited.

Sensory testing revealed diminished pin-prick perception in a length-dependent fashion in the lower extremities, reduced 50% compared with the hands. Gait could not be assessed due to weakness.

Initial laboratory testing

Results of initial laboratory tests—complete blood cell count, complete metabolic panel, erythrocyte sedimentation rate, C-reactive protein, thyroid-stimulating hormone, and hemoglobin A_1c—were unremarkable.

 

 

FURTHER EVALUATION AND DIFFERENTIAL DIAGNOSIS

1. Which of the following is the most likely diagnosis at this point?

• Cerebral infarction
• Guillain-Barré syndrome
• Progressive polyneuropathy
• Transverse myelitis
• Polyradiculopathy

In the absence of definitive diagnostic tests, all of the above options were considered in the differential diagnosis for this patient.

Cerebral infarction

Although acute-onset diplopia can be explained by brainstem stroke involving cranial nerve nuclei or their projections, the onset of diplopia with progressive bilateral lower-extremity weakness makes stroke unlikely. Flaccid paralysis, areflexia of the lower extremities, and sensory involvement can also be caused by acute anterior spinal artery occlusion leading to spinal cord infarction; however, the deficits are usually maximal at onset.

Guillain-Barré syndrome

The combination of acute-subacute progressive ascending weakness, sensory involvement, and diminished or absent reflexes is typical of Guillain-Barré syndrome. Cranial nerve involvement can overlap with the more typical features of the syndrome. However, most patients reach the nadir of their disease by 4 weeks after initial symptom onset, even without treatment.¹ This patient’s condition continued to worsen over 8 weeks. In addition, the asymmetric lower-extremity weakness and sparing of the arms are atypical for Guillain-Barré syndrome.

Given the progression of symptoms, chronic inflammatory demyelinating polyneuropathy is also a consideration, typically presenting as a relapsing or progressive neuropathy in proximal and distal muscles and worsening over at least an 8-week period.²

The initial workup for Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy includes lumbar puncture to assess for albuminocytologic dissociation (elevated protein with normal white blood cell count) in cerebrospinal fluid (CSF), and electromyography (EMG) to assess for neuro­physiologic evidence of peripheral nerve demyelination. In Miller-Fisher syndrome, a rare variant of Guillain-Barré syndrome characterized by ataxia, ophthalmoparesis, and areflexia, serum ganglioside antibodies to GQ1b are found in over 90% of patients.^3,4 Although MRI of the spine is not necessary to diagnose Guillain-Barré syndrome, it is often done to exclude other causes of lower-extremity weakness such as spinal cord or cauda equina compression that would require urgent neurosurgical consultation. MRI can support the diagnosis of Guillain-Barré syndrome when it reveals enhancement of the spinal nerve roots or cauda equina.

Other polyneuropathies

Polyneuropathy is caused by a variety of diseases that affect the function of peripheral motor, sensory, or autonomic nerves. The differential diagnosis is broad and involves inflammatory diseases (including autoimmune and paraneoplastic causes), hereditary disorders, infection, toxicity, and ischemic and nutritional deficiencies.⁵ Polyneuropathy can present in a distal-predominant, generalized, or asymmetric pattern involving individual nerve trunks termed “mononeuropathy multiplex,” as in our patient’s presentation. The initial workup includes EMG and a battery of serologic tests. In cases of severe and progressive polyneuropathy, nerve biopsy can assess for the presence of vasculitis, amyloidosis, and paraprotein deposition.

Transverse myelitis

Transverse myelitis is an inflammatory myelopathy that usually presents with acute or subacute weakness of the upper extremities or lower extremities, or both, corresponding to the level of the lesion, hyperreflexia, bladder and bowel dysfunction, spinal level of sensory loss, and autonomic involvement.⁶ The differential diagnosis of acute myelopathy includes:

• Infection (eg, herpes simplex virus, West Nile virus, Lyme disease, Mycoplasma pneumoniae, human immunodeficiency virus)
• Systemic inflammatory disease (systemic lupus erythematosus, sarcoidosis, Sjögren syndrome, scleroderma, paraneoplastic syndrome)
• Central nervous system demyelinating disease (acute disseminated encephalomyelitis, multiple sclerosis, neuromyelitis optica)
• Vascular malformation (dural arteriovenous fistula)
• Compression due to tumor, bleeding, disc herniation, infection, or abscess.

The workup involves laboratory tests to exclude systemic inflammatory and infectious causes, as well as MRI of the spine with and without contrast to identify a causative lesion. Lumbar puncture and CSF analysis may show pleocytosis, elevated protein concentration, and increased intrathecal immunoglobulin G (IgG) index.⁷

Although our patient’s presentation with subacute lower-extremity weakness, sensory changes, and bladder dysfunction were consistent with transverse myelitis, her cranial nerve abnormalities would be atypical for it.

Polyradiculopathy


Polyradiculopathy has many possible causes. In the United States, the most common causes are lumbar spondylosis, lumbar canal stenosis, and diabetic polyradiculoneuropathy.

When multiple spinal segments are affected, leptomeningeal disease involving the arachnoid and pia mater should be considered. Causes include malignant invasion, inflammatory cell accumulation, and protein deposition, leading to patchy but widespread dysfunction of spinal nerve roots and cranial nerves. Specific causes are myriad and include carcinomatous meningitis,⁸ syphilis, tuberculosis, sarcoidosis, and paraproteinemias. CSF and MRI changes are often nonspecific, leading to the need for meningeal biopsy for diagnosis.

 

 

CASE CONTINUED

During her hospitalization, our patient developed acute right upper and lower facial weakness consistent with peripheral facial mononeuropathy. Bilateral lower-extremity weakness progressed to disabling paraparesis.

She underwent lumbar puncture and CSF analysis (Table 1). The most notable findings were significant pleocytosis (72% lymphocytic predominance), protein elevation, and elevated IgG index (indicative of elevated intrathecal immunoglobulin synthesis in the central nervous system). Viral, bacterial, and fungal studies were negative. Guillain-Barré syndrome, other polyneuropathies, and spinal cord infarction would not be expected with these CSF features.

Surface EMG demonstrated normal sensory responses, and needle EMG showed chronic and active motor axon loss in the L3 and S1 root distributions, suggesting polyradiculopathy without polyneuropathy. These findings would not be expected in typical acute transverse myelitis but could be seen with spinal cord infarction.

MRI of the entire spine with and without contrast showed cauda equina nerve root thickening and enhancement, especially involving the L5 and S1 roots (Figure 1). The spinal cord appeared normal. These findings further supported polyradiculopathy and a leptomeningeal process.

Further evaluation included chest radiography, erythrocyte sedimentation rate, C-reactive protein, hemoglobin A_1c, human immunodeficiency virus testing, antinuclear antibody, antineutrophil cytoplasmic antibody, extractable nuclear antibody, GQ1b antibody, serum and CSF paraneoplastic panels, levels of vitamin B₁, B₁₂, and B₆, copper, and ceruloplasmin, and a screen for heavy metals. All results were within normal ranges.

ESTABLISHING THE DIAGNOSIS

Serum monoclonal protein analysis with immunofixation revealed IgM kappa monoclonal gammopathy with an IgM level of 1,570 (reference range 53–334 mg/dL) and M-spike 0.75 (0.00 mg/dL), serum free kappa light chains 61.1 (3.30–19.40 mg/L), lambda 9.3 (5.7–26.3 mg/L), and kappa-lambda ratio 6.57 (0.26–1.65).

2. Which is the best next step in this patient’s neurologic evaluation?

• Test CSF angiotensin-converting enzyme level
• CSF cytology
• Meningeal biopsy
• Peripheral nerve biopsy

Given the high suspicion for malignancy, CSF cytology was performed and showed increased numbers of mononuclear chronic inflammatory cells, including a mixture of lymphocytes and monocytes, favoring a reactive lymphoid pleocytosis. Flow cytometry indicated the presence of a monoclonal, CD5- and CD10- negative, B-cell lymphoproliferative disorder. The immunophenotypic findings were not specific for a single diagnosis. The differential diagnosis included marginal zone lymphoma and lymphoplasmacytic lymphoma.

3. Given the presence of serum IgM monoclonal gammopathy in this patient, which is the most likely diagnosis?

• Neurosarcoidosis
• Multiple myeloma
• Waldenström macroglobulinemia
• Carcinomatous meningitis

Study of bone marrow biopsy demonstrated limited bone marrow involvement (1%) by a lymphoproliferative disorder with plasmacytoid features, and DNA testing detected an MYD88 L265P mutation, reported to be present in 90% of patients with Waldenström macroglobulinemia.⁹ This finding confirmed the diagnosis of Waldenström macroglobulinemia with central nervous system involvement. Our patient began therapy with rituximab and methotrexate, which resulted in some improvement in strength, gait, and vision.

 

 

WALDENSTRÖM MACROGLOBULINEMIA AND BING-NEEL SYNDROME

Waldenström macroglobulinemia is a lympho­plasmacytic lymphoma associated with a monoclonal IgM protein.¹⁰ It is considered a paraproteinemic disorder, similar to multiple myeloma. The presenting symptoms and complications are related to direct tumor infiltration, hyperviscosity syndrome, and deposition of IgM in various tissues.^11,12

Waldenström macroglobulinemia is usually indolent, and treatment is reserved for patients with symptoms.^13,14 It includes rituximab, usually in combination with chemotherapy or other targeted agents.^15,16

Paraneoplastic antibody-mediated polyneuropathy may occur in these patients. However, the pattern is usually symmetrical clinically, with demyelination on EMG, and is not associated with cranial nerve or meningeal involvement. Management with plasmapheresis, corticosteroids, and intravenous immunoglobulin has not been shown to be effective.¹⁷

Involvement of the central nervous system as a complication of Waldenström macroglobulinemia has been described as Bing-Neel syndrome. It can present as diffuse malignant cell infiltration of the leptomeningeal space, white matter, or spinal cord, or in a tumoral form presenting as intraparenchymal masses or nodular lesions. The distinction between the tumoral and diffuse forms is based primarily on imaging findings.¹⁸

In a report of 44 patients with Bing-Neel syndrome, 36% presented with the disorder as the initial manifestation of Waldenström macroglobulinemia.¹⁸ The primary presenting symptoms were imbalance and gait difficulty (48%) and cranial nerve involvement (36%), which presented as predominantly facial or oculomotor nerve palsy. Cauda equina syndrome with motor involvement (seen in our patient) occurred in 14% of patients. Other presenting symptoms included cognitive impairment, sensory deficits, headache, dysarthria, aphasia, and seizures.

LEARNING POINTS

The differential diagnosis for patients presenting with multifocal neurologic symptoms can be broad, and a systematic approach to the diagnosis is necessary. Localizing the lesion is important in determining the diagnosis for patients presenting with neurologic symptoms. The process of localization begins with taking the history, is further refined during the examination, and is confirmed with diagnostic studies. Atypical presentations of relatively common neurologic diseases such as Guillain-Barré syndrome, transverse myelitis, and peripheral polyneuropathy do occur, but uncommon diagnoses need to be considered when support for the initial diagnosis is lacking.

To the Editor: The review by May et al¹ of 3 neglected numbers in the complete blood cell count (CBC) was a good reminder to look more closely at the results of the CBCs we often order in primary care. I was surprised to see no mention of the red cell distribution width in relation to another cardiovascular disorder—obstructive sleep apnea.^2,3 I wonder if the authors would comment on this association?

To the Editor: The review by May et al¹ of 3 neglected numbers in the complete blood cell count (CBC) was a good reminder to look more closely at the results of the CBCs we often order in primary care. I was surprised to see no mention of the red cell distribution width in relation to another cardiovascular disorder—obstructive sleep apnea.^2,3 I wonder if the authors would comment on this association?

To the Editor: The review by May et al¹ of 3 neglected numbers in the complete blood cell count (CBC) was a good reminder to look more closely at the results of the CBCs we often order in primary care. I was surprised to see no mention of the red cell distribution width in relation to another cardiovascular disorder—obstructive sleep apnea.^2,3 I wonder if the authors would comment on this association?

In Reply: We thank Dr. Homler for his question and for highlighting another important disease state, obstructive sleep apnea, in which a high red cell distribution width (RDW) has correlated with disease severity.^1,2 The 2 retrospective studies he mentioned indicated that RDW is negatively correlated with metrics such as oxygen saturation, sleep time, and sleep quality. Interestingly, another retrospective study showed that RDW was significantly higher in patients with concurrent obstructive sleep apnea and cardiovascular disease than in patients with obstructive sleep apnea alone, suggesting that the presence of anisocytosis in obstructive sleep apnea may be due to its link to cardiovascular disease.³

Although we focused on cardiovascular disease in our review, RDW has also shown prognostic significance in many other disorders including ischemic stroke,⁴ pneumonia,^5,6 chronic kidney disease,⁷ and gastrointestinal disorders.⁸ Collectively, these studies indicate that RDW may serve as a red flag for clinicians, raising concern for increased disease severity and potential adverse outcomes. However, further research is needed to determine if and how RDW monitoring should be used to prompt interventions to improve patient outcomes.

In Reply: We thank Dr. Homler for his question and for highlighting another important disease state, obstructive sleep apnea, in which a high red cell distribution width (RDW) has correlated with disease severity.^1,2 The 2 retrospective studies he mentioned indicated that RDW is negatively correlated with metrics such as oxygen saturation, sleep time, and sleep quality. Interestingly, another retrospective study showed that RDW was significantly higher in patients with concurrent obstructive sleep apnea and cardiovascular disease than in patients with obstructive sleep apnea alone, suggesting that the presence of anisocytosis in obstructive sleep apnea may be due to its link to cardiovascular disease.³

Although we focused on cardiovascular disease in our review, RDW has also shown prognostic significance in many other disorders including ischemic stroke,⁴ pneumonia,^5,6 chronic kidney disease,⁷ and gastrointestinal disorders.⁸ Collectively, these studies indicate that RDW may serve as a red flag for clinicians, raising concern for increased disease severity and potential adverse outcomes. However, further research is needed to determine if and how RDW monitoring should be used to prompt interventions to improve patient outcomes.

In Reply: We thank Dr. Homler for his question and for highlighting another important disease state, obstructive sleep apnea, in which a high red cell distribution width (RDW) has correlated with disease severity.^1,2 The 2 retrospective studies he mentioned indicated that RDW is negatively correlated with metrics such as oxygen saturation, sleep time, and sleep quality. Interestingly, another retrospective study showed that RDW was significantly higher in patients with concurrent obstructive sleep apnea and cardiovascular disease than in patients with obstructive sleep apnea alone, suggesting that the presence of anisocytosis in obstructive sleep apnea may be due to its link to cardiovascular disease.³

Although we focused on cardiovascular disease in our review, RDW has also shown prognostic significance in many other disorders including ischemic stroke,⁴ pneumonia,^5,6 chronic kidney disease,⁷ and gastrointestinal disorders.⁸ Collectively, these studies indicate that RDW may serve as a red flag for clinicians, raising concern for increased disease severity and potential adverse outcomes. However, further research is needed to determine if and how RDW monitoring should be used to prompt interventions to improve patient outcomes.

Here are 5 articles from the June issue of Clinician Reviews (individual articles are valid for one year from date of publication—expiration dates below):

1. Expert: There’s no single treatment for fibromyalgia

To take the posttest, go to: https://bit.ly/2EAI5v1
Expires February 3, 2020

2. Mood and behavior are different targets for irritability in children

To take the posttest, go to: https://bit.ly/2wpLS9X
Expires February 6, 2020

3. Biomarkers predict VTE risk with menopausal oral hormone therapy

To take the posttest, go to: https://bit.ly/2JKEQFC
Expires February 6, 2020

4. Mild aerobic exercise speeds sports concussion recovery

To take the posttest, go to: https://bit.ly/30RuYiE
Expires February 4, 2020

5. For CABG, multiple and single arterial grafts show no survival difference

To take the posttest, go to: https://bit.ly/2wtiCiF
Expires January 31, 2020

Here are 5 articles from the June issue of Clinician Reviews (individual articles are valid for one year from date of publication—expiration dates below):

1. Expert: There’s no single treatment for fibromyalgia

To take the posttest, go to: https://bit.ly/2EAI5v1
Expires February 3, 2020

2. Mood and behavior are different targets for irritability in children

To take the posttest, go to: https://bit.ly/2wpLS9X
Expires February 6, 2020

3. Biomarkers predict VTE risk with menopausal oral hormone therapy

To take the posttest, go to: https://bit.ly/2JKEQFC
Expires February 6, 2020

4. Mild aerobic exercise speeds sports concussion recovery

To take the posttest, go to: https://bit.ly/30RuYiE
Expires February 4, 2020

5. For CABG, multiple and single arterial grafts show no survival difference

To take the posttest, go to: https://bit.ly/2wtiCiF
Expires January 31, 2020

Here are 5 articles from the June issue of Clinician Reviews (individual articles are valid for one year from date of publication—expiration dates below):

1. Expert: There’s no single treatment for fibromyalgia

To take the posttest, go to: https://bit.ly/2EAI5v1
Expires February 3, 2020

2. Mood and behavior are different targets for irritability in children

To take the posttest, go to: https://bit.ly/2wpLS9X
Expires February 6, 2020

3. Biomarkers predict VTE risk with menopausal oral hormone therapy

To take the posttest, go to: https://bit.ly/2JKEQFC
Expires February 6, 2020

4. Mild aerobic exercise speeds sports concussion recovery

To take the posttest, go to: https://bit.ly/30RuYiE
Expires February 4, 2020

5. For CABG, multiple and single arterial grafts show no survival difference

To take the posttest, go to: https://bit.ly/2wtiCiF
Expires January 31, 2020

Two recent studies that assess the Food and Drug Administration’s accelerated approval process for cancer drugs suggest the agency is using inadequate measures to determine clinical value for patients.

Artfoliophoto/Thinkstock

In the first study, lead investigator Emerson Y. Chen, MD, of Oregon Health & Science University, Portland, and colleagues conducted a retrospective analysis of all drugs approved by the FDA on the basis of response rate – the percentage of patients who experience tumor shrinkage – from Jan. 1, 2006, to Sept. 30, 2018. The data set consisted of 59 oncology drugs with 85 unique indications approved by the FDA for advanced-stage metastatic cancer on the basis of a response rate (RR) endpoint during the study period.

Of the 85 indications, 32 were granted regular approval immediately with limited postmarketing efficacy requirements and 53 (62%) were granted accelerated approval. Of the accelerated approvals, 29 (55%) were later converted to regular approval.

The median RR for the 85 indications was 41%, and the median sample size of such RR trials was 117 patients, according to the analysis published in JAMA Internal Medicine.

Among all approvals, 14 of 85 (16%) had an RR less than 20%, 28 of 85 (33%) had an RR less than 30%, and 40 of 85 (47%) had an RR less than 40%.

Most approved drugs had an RR ranging from 20% to 59%, the study found. Of 81 available indications, the median complete response rate – defined as the percentage of patients with no visible disease and normalization of lymph nodes – was 6%. (Complete response data were not reported for four drug indications.)

The investigators found that many of the drugs studied have remained on the market for years without subsequent confirmatory data. For example, when the accelerated approvals based on RR were converted to full approval, 23 of 29 were made on the basis of surrogate endpoints (progression-free survival or RR), 7 of 29 were made on the basis of RR, and just 6 of 29 were made on the basis of overall survival (OS).

The findings suggest that most cancer drugs approved by the FDA based on RR have less than transformational response rates, and that such indications do not have confirmed clinical benefit, the study authors wrote.

While in some settings, a response can equal prognostic value regarding overall survival, the authors wrote that “the ability of RR to serve as a validated surrogate for OS varies among cancer types and is generally poor.”

In the second study, researchers found that confirmatory trials for only one-fifth of cancer drug indications approved via the FDA’s accelerated approval route demonstrated improvements in overall patient survival.

Lead investigator Bishal Gyawali, MD, PhD, of Queen’s University, Kingston, Ont., and colleagues examined FDA data on recent drugs and indications that received accelerated approval and were later granted full approval.

For their analysis, the investigators reviewed the FDA’s database of postmarketing requirements and commitments, as well as PubMed, to determine the current status of postmarket trials for indications labeled as “ongoing” in the original FDA data.

Of 93 cancer drug indications for which accelerated approval was granted from Dec. 11, 1992, to May 31, 2017, the FDA reported clinical benefit was adequately confirmed in 51 indications. Of these confirmations, 15 demonstrated improvement in overall survival.

In their updated analysis, the investigators determined that confirmatory trials for 19 of the 93 (20%) cancer drug approvals reported an improvement in OS, 19 trials (20%) reported improvement in the same surrogate used in the preapproval trial, and 20 trials (21%) reported improvement in a different surrogate, according to the study, also published in JAMA Internal Medicine.

Additionally, results showed that 5 confirmatory trials were delayed, 10 trials were pending, and 9 trials were ongoing.

For three recent accelerated approvals, the primary endpoints were not met in the confirmatory trials, but one of the indications still received full approval.

The findings raise several concerns about the accelerated cancer drug pathway, including whether the same surrogate efficacy measure should be used as verification of drug benefit, according to the investigators. Conversely, using a different surrogate endpoint than the original measure can cause confusion among physicians and patients about whether the cancer drug improves survival or quality of life, information that is essential in the benefit-risk evaluation for clinical decision making.

That a number of the confirmatory trials examined were delayed or pending emphasize the considerable time that can elapse between drug approval and confirmatory trial completion, they added.

“Timely planning and completion of postmarketing trials is necessary for proper implementation of the accelerated approval pathway, and the FDA should minimize the period during which patients and physicians are using drugs approved through accelerated pathways without rigorous data on their ultimate clinical benefit,” the authors wrote in the analysis.

Dr. Chen, lead author of the RR study, said both studies call into question what criteria is optimal when assessing cancer drug value, while ensuring such measurements are not too high to achieve – preventing useful drugs to market – but also not too low – allowing drugs with marginal benefit into the market.

“There has been tremendous drug development within the oncology space, and it is always important to look back to reassess and see if the process [matches] the original vision so that we can correct any misuse or concerns,” Dr. Chen said in an interview.

Dr. Chen said his study indicates the RR endpoint has been misused in scenarios with low response rate, common cancer, and/or situations with already available therapies. In the study by Dr. Gyawali, the results suggest many drugs approved on the basis of a surrogate endpoint (RR or progression-free survival) ultimately do not demonstrate survival benefit confirmation or patient-reported benefit, Dr. Chen said.

“We hope that readers of these JAMA IM studies and the accompanying commentaries will recognize that there could be a set of guidance criteria from regulatory agencies or oncology organizations to recommend use of surrogate endpoints in special situations: high response rate of the drug, very rare cancer, or highly innovative therapy not yet seen before,” he said. “The use of surrogate endpoints to justify these therapies must also have postmarketing confirmation of survival or patient-reported benefit.”

The study led by Dr. Chen was supported by the Laura and John Arnold Foundation. Dr Chen reported receiving lecture honorarium from Horizon CME; another coauthor reported receiving honorarium from universities, medical centers, and publishers. The study led by Dr. Gyawali was supported by the Arnold Ventures; one of the coauthors reported receiving grant support from the Harvard-MIT Center for Regulatory Science and the Engelberg Foundation, as well as unrelated research funding from the FDA.

agallegos@mdedge.com

SOURCES: Chen EY et al. JAMA Intern Med. 2019 May 28. doi: 10.1001/jamainternmed.2019.0583; Gyawali B et al. JAMA Intern Med. 2019 May 28. doi: 10.1001/jamainternmed.2019.0462.

Two recent studies that assess the Food and Drug Administration’s accelerated approval process for cancer drugs suggest the agency is using inadequate measures to determine clinical value for patients.

Artfoliophoto/Thinkstock

In the first study, lead investigator Emerson Y. Chen, MD, of Oregon Health & Science University, Portland, and colleagues conducted a retrospective analysis of all drugs approved by the FDA on the basis of response rate – the percentage of patients who experience tumor shrinkage – from Jan. 1, 2006, to Sept. 30, 2018. The data set consisted of 59 oncology drugs with 85 unique indications approved by the FDA for advanced-stage metastatic cancer on the basis of a response rate (RR) endpoint during the study period.

Of the 85 indications, 32 were granted regular approval immediately with limited postmarketing efficacy requirements and 53 (62%) were granted accelerated approval. Of the accelerated approvals, 29 (55%) were later converted to regular approval.

The median RR for the 85 indications was 41%, and the median sample size of such RR trials was 117 patients, according to the analysis published in JAMA Internal Medicine.

Among all approvals, 14 of 85 (16%) had an RR less than 20%, 28 of 85 (33%) had an RR less than 30%, and 40 of 85 (47%) had an RR less than 40%.

Most approved drugs had an RR ranging from 20% to 59%, the study found. Of 81 available indications, the median complete response rate – defined as the percentage of patients with no visible disease and normalization of lymph nodes – was 6%. (Complete response data were not reported for four drug indications.)

The investigators found that many of the drugs studied have remained on the market for years without subsequent confirmatory data. For example, when the accelerated approvals based on RR were converted to full approval, 23 of 29 were made on the basis of surrogate endpoints (progression-free survival or RR), 7 of 29 were made on the basis of RR, and just 6 of 29 were made on the basis of overall survival (OS).

The findings suggest that most cancer drugs approved by the FDA based on RR have less than transformational response rates, and that such indications do not have confirmed clinical benefit, the study authors wrote.

While in some settings, a response can equal prognostic value regarding overall survival, the authors wrote that “the ability of RR to serve as a validated surrogate for OS varies among cancer types and is generally poor.”

In the second study, researchers found that confirmatory trials for only one-fifth of cancer drug indications approved via the FDA’s accelerated approval route demonstrated improvements in overall patient survival.

Lead investigator Bishal Gyawali, MD, PhD, of Queen’s University, Kingston, Ont., and colleagues examined FDA data on recent drugs and indications that received accelerated approval and were later granted full approval.

For their analysis, the investigators reviewed the FDA’s database of postmarketing requirements and commitments, as well as PubMed, to determine the current status of postmarket trials for indications labeled as “ongoing” in the original FDA data.

Of 93 cancer drug indications for which accelerated approval was granted from Dec. 11, 1992, to May 31, 2017, the FDA reported clinical benefit was adequately confirmed in 51 indications. Of these confirmations, 15 demonstrated improvement in overall survival.

In their updated analysis, the investigators determined that confirmatory trials for 19 of the 93 (20%) cancer drug approvals reported an improvement in OS, 19 trials (20%) reported improvement in the same surrogate used in the preapproval trial, and 20 trials (21%) reported improvement in a different surrogate, according to the study, also published in JAMA Internal Medicine.

Additionally, results showed that 5 confirmatory trials were delayed, 10 trials were pending, and 9 trials were ongoing.

For three recent accelerated approvals, the primary endpoints were not met in the confirmatory trials, but one of the indications still received full approval.

The findings raise several concerns about the accelerated cancer drug pathway, including whether the same surrogate efficacy measure should be used as verification of drug benefit, according to the investigators. Conversely, using a different surrogate endpoint than the original measure can cause confusion among physicians and patients about whether the cancer drug improves survival or quality of life, information that is essential in the benefit-risk evaluation for clinical decision making.

That a number of the confirmatory trials examined were delayed or pending emphasize the considerable time that can elapse between drug approval and confirmatory trial completion, they added.

“Timely planning and completion of postmarketing trials is necessary for proper implementation of the accelerated approval pathway, and the FDA should minimize the period during which patients and physicians are using drugs approved through accelerated pathways without rigorous data on their ultimate clinical benefit,” the authors wrote in the analysis.

Dr. Chen, lead author of the RR study, said both studies call into question what criteria is optimal when assessing cancer drug value, while ensuring such measurements are not too high to achieve – preventing useful drugs to market – but also not too low – allowing drugs with marginal benefit into the market.

“There has been tremendous drug development within the oncology space, and it is always important to look back to reassess and see if the process [matches] the original vision so that we can correct any misuse or concerns,” Dr. Chen said in an interview.

Dr. Chen said his study indicates the RR endpoint has been misused in scenarios with low response rate, common cancer, and/or situations with already available therapies. In the study by Dr. Gyawali, the results suggest many drugs approved on the basis of a surrogate endpoint (RR or progression-free survival) ultimately do not demonstrate survival benefit confirmation or patient-reported benefit, Dr. Chen said.

“We hope that readers of these JAMA IM studies and the accompanying commentaries will recognize that there could be a set of guidance criteria from regulatory agencies or oncology organizations to recommend use of surrogate endpoints in special situations: high response rate of the drug, very rare cancer, or highly innovative therapy not yet seen before,” he said. “The use of surrogate endpoints to justify these therapies must also have postmarketing confirmation of survival or patient-reported benefit.”

The study led by Dr. Chen was supported by the Laura and John Arnold Foundation. Dr Chen reported receiving lecture honorarium from Horizon CME; another coauthor reported receiving honorarium from universities, medical centers, and publishers. The study led by Dr. Gyawali was supported by the Arnold Ventures; one of the coauthors reported receiving grant support from the Harvard-MIT Center for Regulatory Science and the Engelberg Foundation, as well as unrelated research funding from the FDA.

agallegos@mdedge.com

SOURCES: Chen EY et al. JAMA Intern Med. 2019 May 28. doi: 10.1001/jamainternmed.2019.0583; Gyawali B et al. JAMA Intern Med. 2019 May 28. doi: 10.1001/jamainternmed.2019.0462.

Two recent studies that assess the Food and Drug Administration’s accelerated approval process for cancer drugs suggest the agency is using inadequate measures to determine clinical value for patients.

Artfoliophoto/Thinkstock

In the first study, lead investigator Emerson Y. Chen, MD, of Oregon Health & Science University, Portland, and colleagues conducted a retrospective analysis of all drugs approved by the FDA on the basis of response rate – the percentage of patients who experience tumor shrinkage – from Jan. 1, 2006, to Sept. 30, 2018. The data set consisted of 59 oncology drugs with 85 unique indications approved by the FDA for advanced-stage metastatic cancer on the basis of a response rate (RR) endpoint during the study period.

Of the 85 indications, 32 were granted regular approval immediately with limited postmarketing efficacy requirements and 53 (62%) were granted accelerated approval. Of the accelerated approvals, 29 (55%) were later converted to regular approval.

The median RR for the 85 indications was 41%, and the median sample size of such RR trials was 117 patients, according to the analysis published in JAMA Internal Medicine.

Among all approvals, 14 of 85 (16%) had an RR less than 20%, 28 of 85 (33%) had an RR less than 30%, and 40 of 85 (47%) had an RR less than 40%.

Most approved drugs had an RR ranging from 20% to 59%, the study found. Of 81 available indications, the median complete response rate – defined as the percentage of patients with no visible disease and normalization of lymph nodes – was 6%. (Complete response data were not reported for four drug indications.)

The investigators found that many of the drugs studied have remained on the market for years without subsequent confirmatory data. For example, when the accelerated approvals based on RR were converted to full approval, 23 of 29 were made on the basis of surrogate endpoints (progression-free survival or RR), 7 of 29 were made on the basis of RR, and just 6 of 29 were made on the basis of overall survival (OS).

The findings suggest that most cancer drugs approved by the FDA based on RR have less than transformational response rates, and that such indications do not have confirmed clinical benefit, the study authors wrote.

While in some settings, a response can equal prognostic value regarding overall survival, the authors wrote that “the ability of RR to serve as a validated surrogate for OS varies among cancer types and is generally poor.”

In the second study, researchers found that confirmatory trials for only one-fifth of cancer drug indications approved via the FDA’s accelerated approval route demonstrated improvements in overall patient survival.

Lead investigator Bishal Gyawali, MD, PhD, of Queen’s University, Kingston, Ont., and colleagues examined FDA data on recent drugs and indications that received accelerated approval and were later granted full approval.

For their analysis, the investigators reviewed the FDA’s database of postmarketing requirements and commitments, as well as PubMed, to determine the current status of postmarket trials for indications labeled as “ongoing” in the original FDA data.

Of 93 cancer drug indications for which accelerated approval was granted from Dec. 11, 1992, to May 31, 2017, the FDA reported clinical benefit was adequately confirmed in 51 indications. Of these confirmations, 15 demonstrated improvement in overall survival.

In their updated analysis, the investigators determined that confirmatory trials for 19 of the 93 (20%) cancer drug approvals reported an improvement in OS, 19 trials (20%) reported improvement in the same surrogate used in the preapproval trial, and 20 trials (21%) reported improvement in a different surrogate, according to the study, also published in JAMA Internal Medicine.

Additionally, results showed that 5 confirmatory trials were delayed, 10 trials were pending, and 9 trials were ongoing.

For three recent accelerated approvals, the primary endpoints were not met in the confirmatory trials, but one of the indications still received full approval.

The findings raise several concerns about the accelerated cancer drug pathway, including whether the same surrogate efficacy measure should be used as verification of drug benefit, according to the investigators. Conversely, using a different surrogate endpoint than the original measure can cause confusion among physicians and patients about whether the cancer drug improves survival or quality of life, information that is essential in the benefit-risk evaluation for clinical decision making.

That a number of the confirmatory trials examined were delayed or pending emphasize the considerable time that can elapse between drug approval and confirmatory trial completion, they added.

“Timely planning and completion of postmarketing trials is necessary for proper implementation of the accelerated approval pathway, and the FDA should minimize the period during which patients and physicians are using drugs approved through accelerated pathways without rigorous data on their ultimate clinical benefit,” the authors wrote in the analysis.

Dr. Chen, lead author of the RR study, said both studies call into question what criteria is optimal when assessing cancer drug value, while ensuring such measurements are not too high to achieve – preventing useful drugs to market – but also not too low – allowing drugs with marginal benefit into the market.

“There has been tremendous drug development within the oncology space, and it is always important to look back to reassess and see if the process [matches] the original vision so that we can correct any misuse or concerns,” Dr. Chen said in an interview.

Dr. Chen said his study indicates the RR endpoint has been misused in scenarios with low response rate, common cancer, and/or situations with already available therapies. In the study by Dr. Gyawali, the results suggest many drugs approved on the basis of a surrogate endpoint (RR or progression-free survival) ultimately do not demonstrate survival benefit confirmation or patient-reported benefit, Dr. Chen said.

“We hope that readers of these JAMA IM studies and the accompanying commentaries will recognize that there could be a set of guidance criteria from regulatory agencies or oncology organizations to recommend use of surrogate endpoints in special situations: high response rate of the drug, very rare cancer, or highly innovative therapy not yet seen before,” he said. “The use of surrogate endpoints to justify these therapies must also have postmarketing confirmation of survival or patient-reported benefit.”

The study led by Dr. Chen was supported by the Laura and John Arnold Foundation. Dr Chen reported receiving lecture honorarium from Horizon CME; another coauthor reported receiving honorarium from universities, medical centers, and publishers. The study led by Dr. Gyawali was supported by the Arnold Ventures; one of the coauthors reported receiving grant support from the Harvard-MIT Center for Regulatory Science and the Engelberg Foundation, as well as unrelated research funding from the FDA.

agallegos@mdedge.com

SOURCES: Chen EY et al. JAMA Intern Med. 2019 May 28. doi: 10.1001/jamainternmed.2019.0583; Gyawali B et al. JAMA Intern Med. 2019 May 28. doi: 10.1001/jamainternmed.2019.0462.

For patients with newly diagnosed multiple myeloma who are ineligible for autologous stem cell transplantation (ASCT), adding daratumumab to lenalidomide and dexamethasone provides better outcomes than standard therapy alone, based on an interim analysis from the phase 3 MAIA trial.

A greater proportion of patients in the daratumumab group had complete responses and were alive without disease progression after a median follow-up of 28 months, reported lead author Thierry Facon, MD, of the University of Lille (France) and colleagues, who also noted that daratumumab was associated with higher rates of grade 3 or 4 pneumonia, neutropenia, and lymphopenia.

“For patients who are ineligible for stem-cell transplantation, multiagent regimens, including alkylating agents, glucocorticoids, immunomodulatory drugs, proteasome inhibitors, and new agents, are the standard of care,” the investigators wrote in the New England Journal of Medicine.

The findings from MAIA add clarity to the efficacy and safety of daratumumab in this setting, building on previous phase 3 myeloma trials in the same area, such as ALCYONE, CASTOR, and POLLUX, the investigators noted.

MAIA was an open-label, international trial involving 737 patients with newly diagnosed multiple myeloma who were ineligible for ASCT. Patients were randomized in a 1:1 ratio to receive either daratumumab, lenalidomide, and dexamethasone (daratumumab group; n = 368) or lenalidomide and dexamethasone alone (control group; n = 369).

On a 28-day cycle, all patients received oral lenalidomide 25 mg on days 1-21 and oral dexamethasone 40 mg on days 1, 8, 15, and 22. Patients in the daratumumab group received intravenous daratumumab dosed at 16 mg/kg once a week for cycles 1 and 2, every 2 weeks for cycles 3-6, and then every 4 weeks thereafter. Treatment was continued until unacceptable toxic effects or disease progression occurred.

The primary end point was progression-free survival (PFS). Various secondary end points were also evaluated, including time to progression, complete responses, overall survival, and others.

Among the 737 randomized patients, 729 ultimately underwent treatment. The median patient age was 73 years.

Generally, efficacy measures favored adding daratumumab. After a median follow-up of 28.0 months, disease progression or death had occurred in 26.4% of patients in the daratumumab group, compared with 38.8% in the control group.

The median PFS was not reached in the daratumumab group, compared with 31.9 months in the control group. There was a 44% lower risk of disease progression or death among patients who received daratumumab, compared with the control group (hazard ratio, 0.56, P less than .001).

This PFS trend was consistent across most subgroups, including those for sex, age, and race, with the exception of patients with baseline hepatic impairment.

Additional efficacy measures added weight to the apparent benefit of adding daratumumab. For instance, more patients in the daratumumab group achieved a complete response or better (47.6% vs. 24.9%) and were negative for minimum residual disease (24.2% vs. 7.3%).

In terms of safety, more patients in the daratumumab group than the control group developed grade 3 or higher neutropenia (50% vs. 35.3%), lymphopenia (15.1% vs. 10.7%), infections (32.1% vs. 23.3%) or pneumonia (13.7% vs. 7.9%).

In contrast, grade 3 or 4 anemia was less common in the daratumumab group than the control group (11.8% vs. 19.7%). Overall, the rate of serious adverse events was similar for both groups (approximately 63%), as was the rate of adverse events resulting in death (approximately 6%-7%).

“In this trial involving patients with newly diagnosed multiple myeloma who were ineligible for stem-cell transplantation, the addition of daratumumab to lenalidomide and dexamethasone resulted in significantly longer progression-free survival, a higher response rate, an increased depth of response, and a longer duration of response than lenalidomide and dexamethasone alone,” the investigators concluded.

The study was funded by Janssen Research and Development. The investigators reported relationships with Janssen, Celgene, Takeda, Sanofi, and other companies.

SOURCE: Facon T et al. N Engl J Med. 2019;380:2104-15.

For patients with newly diagnosed multiple myeloma who are ineligible for autologous stem cell transplantation (ASCT), adding daratumumab to lenalidomide and dexamethasone provides better outcomes than standard therapy alone, based on an interim analysis from the phase 3 MAIA trial.

A greater proportion of patients in the daratumumab group had complete responses and were alive without disease progression after a median follow-up of 28 months, reported lead author Thierry Facon, MD, of the University of Lille (France) and colleagues, who also noted that daratumumab was associated with higher rates of grade 3 or 4 pneumonia, neutropenia, and lymphopenia.

“For patients who are ineligible for stem-cell transplantation, multiagent regimens, including alkylating agents, glucocorticoids, immunomodulatory drugs, proteasome inhibitors, and new agents, are the standard of care,” the investigators wrote in the New England Journal of Medicine.

The findings from MAIA add clarity to the efficacy and safety of daratumumab in this setting, building on previous phase 3 myeloma trials in the same area, such as ALCYONE, CASTOR, and POLLUX, the investigators noted.

MAIA was an open-label, international trial involving 737 patients with newly diagnosed multiple myeloma who were ineligible for ASCT. Patients were randomized in a 1:1 ratio to receive either daratumumab, lenalidomide, and dexamethasone (daratumumab group; n = 368) or lenalidomide and dexamethasone alone (control group; n = 369).

On a 28-day cycle, all patients received oral lenalidomide 25 mg on days 1-21 and oral dexamethasone 40 mg on days 1, 8, 15, and 22. Patients in the daratumumab group received intravenous daratumumab dosed at 16 mg/kg once a week for cycles 1 and 2, every 2 weeks for cycles 3-6, and then every 4 weeks thereafter. Treatment was continued until unacceptable toxic effects or disease progression occurred.

The primary end point was progression-free survival (PFS). Various secondary end points were also evaluated, including time to progression, complete responses, overall survival, and others.

Among the 737 randomized patients, 729 ultimately underwent treatment. The median patient age was 73 years.

Generally, efficacy measures favored adding daratumumab. After a median follow-up of 28.0 months, disease progression or death had occurred in 26.4% of patients in the daratumumab group, compared with 38.8% in the control group.

The median PFS was not reached in the daratumumab group, compared with 31.9 months in the control group. There was a 44% lower risk of disease progression or death among patients who received daratumumab, compared with the control group (hazard ratio, 0.56, P less than .001).

This PFS trend was consistent across most subgroups, including those for sex, age, and race, with the exception of patients with baseline hepatic impairment.

Additional efficacy measures added weight to the apparent benefit of adding daratumumab. For instance, more patients in the daratumumab group achieved a complete response or better (47.6% vs. 24.9%) and were negative for minimum residual disease (24.2% vs. 7.3%).

In terms of safety, more patients in the daratumumab group than the control group developed grade 3 or higher neutropenia (50% vs. 35.3%), lymphopenia (15.1% vs. 10.7%), infections (32.1% vs. 23.3%) or pneumonia (13.7% vs. 7.9%).

In contrast, grade 3 or 4 anemia was less common in the daratumumab group than the control group (11.8% vs. 19.7%). Overall, the rate of serious adverse events was similar for both groups (approximately 63%), as was the rate of adverse events resulting in death (approximately 6%-7%).

“In this trial involving patients with newly diagnosed multiple myeloma who were ineligible for stem-cell transplantation, the addition of daratumumab to lenalidomide and dexamethasone resulted in significantly longer progression-free survival, a higher response rate, an increased depth of response, and a longer duration of response than lenalidomide and dexamethasone alone,” the investigators concluded.

The study was funded by Janssen Research and Development. The investigators reported relationships with Janssen, Celgene, Takeda, Sanofi, and other companies.

SOURCE: Facon T et al. N Engl J Med. 2019;380:2104-15.

For patients with newly diagnosed multiple myeloma who are ineligible for autologous stem cell transplantation (ASCT), adding daratumumab to lenalidomide and dexamethasone provides better outcomes than standard therapy alone, based on an interim analysis from the phase 3 MAIA trial.

A greater proportion of patients in the daratumumab group had complete responses and were alive without disease progression after a median follow-up of 28 months, reported lead author Thierry Facon, MD, of the University of Lille (France) and colleagues, who also noted that daratumumab was associated with higher rates of grade 3 or 4 pneumonia, neutropenia, and lymphopenia.

“For patients who are ineligible for stem-cell transplantation, multiagent regimens, including alkylating agents, glucocorticoids, immunomodulatory drugs, proteasome inhibitors, and new agents, are the standard of care,” the investigators wrote in the New England Journal of Medicine.

The findings from MAIA add clarity to the efficacy and safety of daratumumab in this setting, building on previous phase 3 myeloma trials in the same area, such as ALCYONE, CASTOR, and POLLUX, the investigators noted.

MAIA was an open-label, international trial involving 737 patients with newly diagnosed multiple myeloma who were ineligible for ASCT. Patients were randomized in a 1:1 ratio to receive either daratumumab, lenalidomide, and dexamethasone (daratumumab group; n = 368) or lenalidomide and dexamethasone alone (control group; n = 369).

On a 28-day cycle, all patients received oral lenalidomide 25 mg on days 1-21 and oral dexamethasone 40 mg on days 1, 8, 15, and 22. Patients in the daratumumab group received intravenous daratumumab dosed at 16 mg/kg once a week for cycles 1 and 2, every 2 weeks for cycles 3-6, and then every 4 weeks thereafter. Treatment was continued until unacceptable toxic effects or disease progression occurred.

The primary end point was progression-free survival (PFS). Various secondary end points were also evaluated, including time to progression, complete responses, overall survival, and others.

Among the 737 randomized patients, 729 ultimately underwent treatment. The median patient age was 73 years.

Generally, efficacy measures favored adding daratumumab. After a median follow-up of 28.0 months, disease progression or death had occurred in 26.4% of patients in the daratumumab group, compared with 38.8% in the control group.

The median PFS was not reached in the daratumumab group, compared with 31.9 months in the control group. There was a 44% lower risk of disease progression or death among patients who received daratumumab, compared with the control group (hazard ratio, 0.56, P less than .001).

This PFS trend was consistent across most subgroups, including those for sex, age, and race, with the exception of patients with baseline hepatic impairment.

Additional efficacy measures added weight to the apparent benefit of adding daratumumab. For instance, more patients in the daratumumab group achieved a complete response or better (47.6% vs. 24.9%) and were negative for minimum residual disease (24.2% vs. 7.3%).

In terms of safety, more patients in the daratumumab group than the control group developed grade 3 or higher neutropenia (50% vs. 35.3%), lymphopenia (15.1% vs. 10.7%), infections (32.1% vs. 23.3%) or pneumonia (13.7% vs. 7.9%).

In contrast, grade 3 or 4 anemia was less common in the daratumumab group than the control group (11.8% vs. 19.7%). Overall, the rate of serious adverse events was similar for both groups (approximately 63%), as was the rate of adverse events resulting in death (approximately 6%-7%).

“In this trial involving patients with newly diagnosed multiple myeloma who were ineligible for stem-cell transplantation, the addition of daratumumab to lenalidomide and dexamethasone resulted in significantly longer progression-free survival, a higher response rate, an increased depth of response, and a longer duration of response than lenalidomide and dexamethasone alone,” the investigators concluded.

The study was funded by Janssen Research and Development. The investigators reported relationships with Janssen, Celgene, Takeda, Sanofi, and other companies.

SOURCE: Facon T et al. N Engl J Med. 2019;380:2104-15.

A genetic analysis of patients with chronic lymphocytic leukemia treated with frontline, rituximab-based regimens found that deletion 11q22 and unmutated IgVH status may predict worse prognosis.

Michaela Spunarova, MD, of Masaryk University, Brno, Czech Republic, and colleagues conducted a genetic analysis of 177 patients with chronic lymphocytic leukemia (CLL). The results of the analysis were published in Leukemia Research.

The study focused on patients with CLL with an intact TP53 gene, looking at recurrently muted genes in CLL, genomic aberrations by fluorescence in situ hybridization, and IgVH status, according to the researchers.

The team analyzed the effects of these mutations on progression-free survival (PFS) following frontline treatment with bendamustine and rituximab (BR) or fludarabine, cyclophosphamide, and rituximab (FCR) therapeutic regimens.

Dr. Spunarova and colleagues used next-generation sequencing to analyze DNA from the patient samples. Data on 11q22, 13q14, trisomy 12, and IgVH mutation status were also considered in the analyses of PFS.

After analysis, the researchers validated that unmutated IgVH status is an indicator of poor prognosis in CLL patients with wild-type TP53 treated with frontline FCR.

When looking at both BR and FCR regimens, a single 11q22 deletion, lacking an ATM mutation on the other allele, resulted in the shortest PFS, at a median of just 16 months.

“Based on our data, special attention should be given to CLL patients harboring a sole 11q22 deletion, with no ATM mutation on the other allele, who manifest particularly short PFS,” they noted.

The researchers acknowledged a key limitation of the study was the small sample size. As a result, the results should be interpreted in a careful manner.

The study was funded by the Ministry of Health of the Czech Republic. The authors reported having no conflicts of interest.

SOURCE: Spunarova M et al. Leuk Res. 2019 Jun;81:75-81.

A genetic analysis of patients with chronic lymphocytic leukemia treated with frontline, rituximab-based regimens found that deletion 11q22 and unmutated IgVH status may predict worse prognosis.

Michaela Spunarova, MD, of Masaryk University, Brno, Czech Republic, and colleagues conducted a genetic analysis of 177 patients with chronic lymphocytic leukemia (CLL). The results of the analysis were published in Leukemia Research.

The study focused on patients with CLL with an intact TP53 gene, looking at recurrently muted genes in CLL, genomic aberrations by fluorescence in situ hybridization, and IgVH status, according to the researchers.

The team analyzed the effects of these mutations on progression-free survival (PFS) following frontline treatment with bendamustine and rituximab (BR) or fludarabine, cyclophosphamide, and rituximab (FCR) therapeutic regimens.

Dr. Spunarova and colleagues used next-generation sequencing to analyze DNA from the patient samples. Data on 11q22, 13q14, trisomy 12, and IgVH mutation status were also considered in the analyses of PFS.

After analysis, the researchers validated that unmutated IgVH status is an indicator of poor prognosis in CLL patients with wild-type TP53 treated with frontline FCR.

When looking at both BR and FCR regimens, a single 11q22 deletion, lacking an ATM mutation on the other allele, resulted in the shortest PFS, at a median of just 16 months.

“Based on our data, special attention should be given to CLL patients harboring a sole 11q22 deletion, with no ATM mutation on the other allele, who manifest particularly short PFS,” they noted.

The researchers acknowledged a key limitation of the study was the small sample size. As a result, the results should be interpreted in a careful manner.

The study was funded by the Ministry of Health of the Czech Republic. The authors reported having no conflicts of interest.

SOURCE: Spunarova M et al. Leuk Res. 2019 Jun;81:75-81.

A genetic analysis of patients with chronic lymphocytic leukemia treated with frontline, rituximab-based regimens found that deletion 11q22 and unmutated IgVH status may predict worse prognosis.

Michaela Spunarova, MD, of Masaryk University, Brno, Czech Republic, and colleagues conducted a genetic analysis of 177 patients with chronic lymphocytic leukemia (CLL). The results of the analysis were published in Leukemia Research.

The study focused on patients with CLL with an intact TP53 gene, looking at recurrently muted genes in CLL, genomic aberrations by fluorescence in situ hybridization, and IgVH status, according to the researchers.

The team analyzed the effects of these mutations on progression-free survival (PFS) following frontline treatment with bendamustine and rituximab (BR) or fludarabine, cyclophosphamide, and rituximab (FCR) therapeutic regimens.

Dr. Spunarova and colleagues used next-generation sequencing to analyze DNA from the patient samples. Data on 11q22, 13q14, trisomy 12, and IgVH mutation status were also considered in the analyses of PFS.

After analysis, the researchers validated that unmutated IgVH status is an indicator of poor prognosis in CLL patients with wild-type TP53 treated with frontline FCR.

When looking at both BR and FCR regimens, a single 11q22 deletion, lacking an ATM mutation on the other allele, resulted in the shortest PFS, at a median of just 16 months.

“Based on our data, special attention should be given to CLL patients harboring a sole 11q22 deletion, with no ATM mutation on the other allele, who manifest particularly short PFS,” they noted.

The researchers acknowledged a key limitation of the study was the small sample size. As a result, the results should be interpreted in a careful manner.

The study was funded by the Ministry of Health of the Czech Republic. The authors reported having no conflicts of interest.

SOURCE: Spunarova M et al. Leuk Res. 2019 Jun;81:75-81.

The Food and Drug Administration is alerting laboratories and providers to a class I recall on Beckman Coulter hematology analyzers because of the potential for inaccurate platelet count results.

A class I recall indicates reasonable probability of serious adverse health consequences or death associated with use, according to the FDA.

The recall is related to the devices’ platelet analyzing function; among other uses, these devices help assess patients fitness for surgery, so a faulty reading on platelet counts could result in increased risk for life-threatening bleeding during a procedure in patients who have unidentified severe thrombocytopenia, according to a statement from the agency.

“Because this may cause serious injury, or even death, to a patient, we are urging health care professionals to be aware of the potential for inaccurate diagnostic results with these analyzers and to take appropriate actions including the use of alternative diagnostic testing or confirming analyzer results with manual scanning or estimate of platelets,” Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health, said in the statement.

The recall applies to the UniCel DxH 800 Coulter Cellular Analysis System, UniCel DxH 600 Coulter Cellular Analysis System, and UniCel DxH 900 Coulter Cellular Analysis System. The faulty devices were first identified in 2018, and the manufacturer released an urgent medical device correction letter at that time. The company has more recently released a software patch for the devices, but the FDA has not yet assessed whether it resolves the problem. The agency has released detailed actions and recommendations related to these devices.

At this time, the FDA is unaware of any serious adverse events that have been directly linked to these devices, but the agency recommends that any events be reported through its MedWatch reporting system.

cpalmer@mdedge.com

The Food and Drug Administration is alerting laboratories and providers to a class I recall on Beckman Coulter hematology analyzers because of the potential for inaccurate platelet count results.

A class I recall indicates reasonable probability of serious adverse health consequences or death associated with use, according to the FDA.

The recall is related to the devices’ platelet analyzing function; among other uses, these devices help assess patients fitness for surgery, so a faulty reading on platelet counts could result in increased risk for life-threatening bleeding during a procedure in patients who have unidentified severe thrombocytopenia, according to a statement from the agency.

“Because this may cause serious injury, or even death, to a patient, we are urging health care professionals to be aware of the potential for inaccurate diagnostic results with these analyzers and to take appropriate actions including the use of alternative diagnostic testing or confirming analyzer results with manual scanning or estimate of platelets,” Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health, said in the statement.

The recall applies to the UniCel DxH 800 Coulter Cellular Analysis System, UniCel DxH 600 Coulter Cellular Analysis System, and UniCel DxH 900 Coulter Cellular Analysis System. The faulty devices were first identified in 2018, and the manufacturer released an urgent medical device correction letter at that time. The company has more recently released a software patch for the devices, but the FDA has not yet assessed whether it resolves the problem. The agency has released detailed actions and recommendations related to these devices.

At this time, the FDA is unaware of any serious adverse events that have been directly linked to these devices, but the agency recommends that any events be reported through its MedWatch reporting system.

cpalmer@mdedge.com

The Food and Drug Administration is alerting laboratories and providers to a class I recall on Beckman Coulter hematology analyzers because of the potential for inaccurate platelet count results.

A class I recall indicates reasonable probability of serious adverse health consequences or death associated with use, according to the FDA.

The recall is related to the devices’ platelet analyzing function; among other uses, these devices help assess patients fitness for surgery, so a faulty reading on platelet counts could result in increased risk for life-threatening bleeding during a procedure in patients who have unidentified severe thrombocytopenia, according to a statement from the agency.

“Because this may cause serious injury, or even death, to a patient, we are urging health care professionals to be aware of the potential for inaccurate diagnostic results with these analyzers and to take appropriate actions including the use of alternative diagnostic testing or confirming analyzer results with manual scanning or estimate of platelets,” Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health, said in the statement.

The recall applies to the UniCel DxH 800 Coulter Cellular Analysis System, UniCel DxH 600 Coulter Cellular Analysis System, and UniCel DxH 900 Coulter Cellular Analysis System. The faulty devices were first identified in 2018, and the manufacturer released an urgent medical device correction letter at that time. The company has more recently released a software patch for the devices, but the FDA has not yet assessed whether it resolves the problem. The agency has released detailed actions and recommendations related to these devices.

At this time, the FDA is unaware of any serious adverse events that have been directly linked to these devices, but the agency recommends that any events be reported through its MedWatch reporting system.

cpalmer@mdedge.com