Interference of rivaroxaban in one-stage and chromogenic factor VIII:C assays

Clinical utility and impact of the use of the chromogenic vs one-stage factor activity assays in haemophilia A and B

Treatment of haemophilia A/B patients comprises factor VIII (FVIII) or factor IX (FIX) concentrate replacement therapy, respectively. FVIII and FIX activity levels can be measured in clinical laboratories using one‐stage activated partial thromboplastin time (aPTT)‐based clotting or two‐stage chromogenic factor activity assays. We discuss strengths and limitations of these assays, providing examples of clinical scenarios to highlight some of the challenges associated with their current use for diagnostic and monitoring purposes. Substantial inter‐laboratory variability has been reported for one‐stage assays when measuring the activity of factor replacement products due to the wide range of currently available aPTT reagents, calibration standards, factor‐deficient plasmas, assay conditions and instruments. Chromogenic activity assays may avoid some limitations associated with one‐stage assays, but their regulatory status, perceived higher cost, and lack of laboratory expertise may influence their use. Haemophilia management guidelines recommend the differential application of one or both assays for initial diagnosis and disease severity characterisation, post‐infusion monitoring and replacement factor potency labelling. Efficient communication between clinical and laboratory staff is crucial to ensure application of the most appropriate assay to each clinical situation, correct interpretation of assay results and, ultimately, accurate diagnosis and optimal and safe treatment of haemophilia A or B patients.

Measurement of coagulation factors during rivaroxaban and apixaban treatment: Results from two crossover trials

BACKGROUND

Prediction models for venous thromboembolism recurrence will likely be improved by adding levels of coagulation factors. Risk assessment is ideally performed during anticoagulant treatment, however, the influence of direct oral anticoagulants on coagulation factors is uncertain.

OBJECTIVE

To assess the influence of rivaroxaban and apixaban on several coagulation factor levels.

METHODS

In two crossover trials we assessed the influence of rivaroxaban and apixaban intake on factor (F)VIII, FXI and FXII-activity and fibrinogen, von Willebrand factor (VWF:Ag), and d-dimer levels. At three sessions with a washout period in between, blood was taken from 12 healthy male individuals immediately before intake of rivaroxaban 15 mg twice daily (n = 6) or apixaban 10 mg twice daily (n = 6) and three hours after the last intake.

RESULTS

Overall, measured levels were lower after rivaroxaban/apixaban intake. The paired mean difference after rivaroxaban intake was -38 IU/dL (95% CI -43; -33) for FVIII:C, -29 U/dL (95% CI -45; -12) for FXI:C, -22 IU/dL (95% CI -43; -1) for FXII:C, -0.11 g/L (95% CI -0.25; 0.03) for fibrinogen, -7 IU/dL (95% CI -18; 3) for VWF:Ag, -27 ng/mL (95% CI -50; -4) for d-dimer and -0.36 (95% CI -0.57; -0.15) for Ln d-dimer. After apixaban intake this was -29 IU/dL (95% CI -38; -21) for FVIII:C, -29 IU/dL (95% CI -36; -22) for FXI:C, -19 IU/dL (95% CI -24; -15) for FXII:C, -0.18 g/L (95% CI -0.33; 0.03) for fibrinogen, -52 ng/mL (95% CI -100; -4) for d-dimer, 0.25 (-0.60; 0.09) for Ln d-dimer and 1 IU/dL (95% CI -7; 9) for VWF:Ag.

CONCLUSION

FVIII:C, FXI:C, FXII:C, and d-dimer measurements were influenced by rivaroxaban/apixaban intake, while fibrinogen and VWF:Ag were not.

Management consensus guidance for the use of rivaroxaban – an oral, direct factor Xa inhibitor

A number of novel oral anticoagulants that directly target factor Xa or thrombin have been developed in recent years. Rivaroxaban and apixaban (direct factor Xa inhibitors) and dabigatran etexilate (a direct thrombin inhibitor) have shown considerable promise in large-scale, randomised clinical studies for the management of thromboembolic disorders, and have been approved for clinical use in specific indications. Rivaroxaban is licensed for the prevention of venous thromboembolism in patients undergoing elective hip or knee replacement surgery, the treatment of deep-vein thrombosis and prevention of recurrent venous thromboembolism, and for stroke prevention in patients with non-valvular atrial fibrillation. Based on the clinical trial data for rivaroxaban, feedback on its use in clinical practice and the authors’ experience with the use of rivaroxaban, practical guidance for the use of rivaroxaban in special patient populations and specific clinical situations is provided. Although most recommendations are in line with the European summary of product characteristics for the approved indications, additional and, in several areas, different recommendations are given based on review of the literature and the authors’ clinical experience.

Ex vivo effects of low-dose rivaroxaban on specific coagulation assays and coagulation factor activities in patients under real life conditions

Global coagulation assays display variable effects at different concentrations of rivaroxaban. The aim of this study is to quantify the ex vivo effects of low-dose rivaroxaban on thrombophilia screening assays and coagulation factor activities based on the administration time, and to show how to mask possible interferences. Plasma samples from 40 patients receiving rivaroxaban 10 mg daily were investigated to measure activities of clotting factor II, V, VII, VIII, IX, XI, XII and XIII; protein C- and protein S-levels; lupus anticoagulants; anticardiolipin IgG and IgM; D-dimer, heparin-platelet factor 4 (HPF4) antibodies and screening tests for von Willebrand disease (VWD). Two hours after rivaroxaban administration, the activities of clotting factors were significantly decreased to different extents, except for factor XIII. Dilution of plasma samples resulted in neutralisation of these interferences. The chromogenic protein C activity assay was not affected by rivaroxaban. Depending on the timing of tablet intake in relation to blood sampling protein S activity was measured falsely high when a clotting assay was used. False-positive results for lupus anticoagulants were observed depending on the assay system used and the administration time of rivaroxaban. ELISA-based assays such as anticardiolipin IgG and IgM, D-dimer, HPF4-antibodies and the turbidimetric assays for VWD were not affected by rivaroxaban. Specific haemostasis clotting tests should be performed directly prior to rivaroxaban intake. Assay optimisation in the presence of rivaroxaban can be achieved by plasma dilution. Immunologic assays are not influenced by rivaroxaban, while chromogenic assays can be used, when they do not depend on factor Xa.

Direct Oral Anticoagulants: Monitoring Anticoagulant Effect

In some clinical settings laboratory measurement of direct oral anticoagulants effect is helpful in guiding medical care, such as life-threatening bleeding, need for emergency surgery, renal impairment, severe hepatic failure, extremes of body weight, or in patients with bleeding or thrombosis on therapy. This article reviews approaches to laboratory testing to assess the anticoagulant effect of these drugs. Because of the wide variation in levels measured in patients on therapy and minimal clinical data from dose adjustment, dose adjustment based on levels is not currently advised. In addition, these drugs interfere with many clot-based laboratory tests and caution is advised in interpreting these tests in patients on direct oral anticoagulants.

Steps to diagnosis of a case of surreptitious intake of one of the newer direct oral anticoagulants: a case report and literature review

Little is known about the effects of newer oral anticoagulants on various coagulation factors. When presented with a case of intentional or suspected overdose with an abnormal coagulation profile, it is imperative to have a working diagnostic algorithm to narrow the cause to a specific drug or drug class. This may become more crucial and time sensitive when dealing with a case of acute hemorrhage. Here we discuss the first reported case of what appears to be a surreptitious intake of newer oral anticoagulants and the steps leading to the diagnosis.

Predictive value of factor VIII levels for recurrent venous thrombosis: results from the MEGA follow-up study

BACKGROUND

Prediction of recurrent venous thrombosis remains a challenge in the clinic.

OBJECTIVE

To investigate the predictive value of coagulation factor VIII (FVIII) levels for recurrent venous thrombosis.

PATIENTS/METHODS

Patients, aged 18-70 years with a first venous thrombosis, were followed from discontinuation of anticoagulant treatment (1999-2010 MEGA follow-up study). The levels of FVIII activity, FVIII antigen and von Willebrand factor (VWF) antigen were measured at least 3 months after cessation of anticoagulant treatment.

RESULTS

Of 2242 patients followed for a median of 6.9 years, 343 developed recurrent thrombosis (incidence rate 2.7/100 patient-years; 95% confidence interval [CI] 2.5-3.1). Recurrence rates steadily increased with higher FVIII activity levels, from 1.4 (95% CI 1.0-1.9), 2.3 (95% CI 1.8-2.9), 3.0 (95% CI 2.4-3.7), 3.2 (95% CI 2.5-4.1), 3.9 (95% CI 2.8-5.3) to 5.1 (95% CI 3.8-6.8) per 100 patient-years, for levels ranging from < 100 IU dL(-1) to > 200 IU dL(-1) . Patients in the highest category of FVIII (> 200 IU dL(-1) ) had a three-fold higher recurrence rate than patients in the lowest category (≤ 100 IU dL(-1) ) (hazard ratio 3.4; 95% CI 2.2-5.3). Results were similar for FVIII antigen and VWF antigen levels, in several sensitivity analyses, and FVIII predicted recurrence rates over a long time period. Within subgroups of patients currently assumed to have low recurrence risks, a high level of FVIII was still predictive for recurrences. Adding FVIII to an existing prediction model (DASH score) improved its predictive value, and, after replacement of D-dimer with FVIII, the model performed equally well, if not better.

CONCLUSIONS

FVIII predicted recurrence in a dose-response fashion, overall and in several subgroups, and is a strong candidate component of recurrence prediction tools.

Chromogenic factor VIII activity assay

Factor VIII (FVIII) may be measured by three different methodologies in the clinical laboratory: one-stage clotting assay, two-stage clotting assay, and chromogenic assay. These assays differ in ease of use, variety of reagents available, sensitivity to mild hemophilia A, and interference from lupus anticoagulants. This review will outline the methodology for each of the FVIII activity assays, with a discussion of assay interferences and variability. In some cases, chromogenic FVIII activity assays may be preferable to clot-based assays, and these clinical situations will be reviewed as well.

Rivaroxaban: a review of its use in the prevention of stroke and systemic embolism in patients with atrial fibrillation

Rivaroxaban (Xarelto(®)), a direct factor Xa inhibitor, is approved for the prevention of stroke and systemic embolism in patients with atrial fibrillation (AF) in Canada or those with nonvalvular AF (NVAF) in the EU, US and Japan. It is administered at a fixed oral dose and generally does not require routine monitoring of coagulation parameters. In the ROCKET AF trial in patients with NVAF and a moderate to high risk of stroke, oral rivaroxaban 20 mg once daily (15 mg once daily in patients with moderate renal impairment) was noninferior to oral dose-adjusted warfarin once daily in preventing primary endpoint events (i.e. stroke and systemic embolism) in the per-protocol population (primary noninferiority analysis) and superior in the on-treatment safety population (primary superiority analysis). Several ROCKET AF subgroup analyses indicated that the treatment effect of rivaroxaban was consistent across patient subgroups stratified according to baseline factors, including the presence or absence of previous stroke or transient ischaemic attack. Patients with moderate renal impairment receiving the reduced rivaroxaban dosage (15 mg once daily) showed a treatment effect consistent with that seen with rivaroxaban 20 mg once daily in patients with normal renal function. The tolerability profile of rivaroxaban was generally acceptable in ROCKET AF, with no significant difference between rivaroxaban and warfarin in the incidence of major or nonmajor clinically-relevant bleeding events (primary safety endpoint). In the Japanese ROCKET AF trial, rivaroxaban 15 mg once daily (10 mg once daily in patients with moderate renal impairment) was noninferior to oral dose-adjusted warfarin once daily in the incidence of major or nonmajor clinically-relevant bleeding (primary study outcome). Thus, rivaroxaban is a reasonable alternative to warfarin for the prevention of stroke and systemic embolism in patients with NVAF.

Monitoring target specific anticoagulants

New, target specific, oral anticoagulants have been shown to be safe and effective in prevention and treatment of thromboembolism without laboratory monitoring. However, clinical use of the drugs dabigatran, rivaroxaban, and apixaban requires laboratory measurement of their anticoagulant effect in specific clinical situations. This paper reviews the data available on use of screening and specialized testing to measure the anticoagulant effect and drug levels in patients prescribed these medications. Their effect on other coagulation assays is also reviewed.

Laboratory testing of rivaroxaban in routine clinical practice: when, how, and which assays

A number of target-specific oral anticoagulants (TSOAs) have been developed in recent years, and some have shown considerable promise in large-scale, randomized clinical trials in the prevention and treatment of thromboembolism. Unlike traditional anticoagulants, such as vitamin K antagonists, these TSOAs exhibit predictable pharmacokinetics and pharmacodynamics. Among these agents, rivaroxaban, a direct Factor Xa inhibitor, has been approved for clinical use in many countries for the management of several thromboembolic disorders. As with the other TSOAs, rivaroxaban is given at fixed doses without routine coagulation monitoring. However, in certain patient populations or special clinical circumstances, measurement of drug exposure may be useful, such as in suspected overdose, in patients with a haemorrhagic or thromboembolic event during treatment with an anticoagulant, in those with acute renal failure, or in patients who require urgent surgery. This article summarizes the influence of rivaroxaban on commonly used coagulation assays and provides practical guidance on laboratory testing of rivaroxaban in routine practice. Both quantitative measurement (using the anti-Factor Xa method) and qualitative measurement (using prothrombin time, expressed in seconds) are discussed, together with some practical considerations when performing these tests and interpreting the test results.

Assessment of the impact of rivaroxaban on coagulation assays: laboratory recommendations for the monitoring of rivaroxaban and review of the literature

INTRODUCTION

Rivaroxaban does not require monitoring nor frequent dose adjustment. However, searching for the optimal dose in the individual patient may be useful in some situations.

AIM

To determine which coagulation assay could be used to assess the impact of rivaroxaban on haemostasis and provide guidelines for the interpretation of routine lab tests.

MATERIALS

Rivaroxaban was spiked at concentrations ranging from 11 to 1,090 ng/mL in plateletpoor plasma. A large panel of coagulation assays was tested.

RESULTS

A concentration dependent prolongation of aPTT, PT, dPT, PiCT was observed. PT and dPT were the most sensitive chronometric assays but results varied depending on the reagent (Triniclot PT Excel S>Recombiplastin 2G>Neoplastin R>Neoplastin CI+>Triniclot PT Excel>Triniclot PT HTF>Innovin). FXa chromogenic assays showed the highest sensitivity. In TGA, Cmax was the most sensitive parameter with the tissue factor induced pathway. Rivaroxaban interferes on haemostasis diagnostic tests such the measurement of clotting factors, fibrinogen, antithrombin, proteins C and S, activated protein-C resistance and Xa-based chomogenic assays.

CONCLUSIONS

PT may be used as screening test to assess the risk of bleedings. A more specific and sensitive assay such as Biophen DiXaI using calibrators should be used to confirm the concentration of rivaroxaban. We also propose cut-off associated with a bleeding or thrombosis risk based on pharmacokinetic studies. Standardization of the time between the last intake of rivaroxaban and the sampling is mandatory.