Adsorption of dabigatran in plasma samples containing the drug neutralizes its activity as efficiently as the addition of idarucizumab. This method allows the evaluation of thrombophilia markers without interruption of anticoagulation therapy or the detection of hemostasis disorders in patients treated with the drug.

To cite this article: Jacquemin M, Toelen J, Schoeters J, van Horenbeeck I, Vanlinthout I, Debasse M, Peetermans M, Vanassche T, Peerlinck K, van Ryn J, Verhamme P. The addition of idarucizumab to plasma samples containing dabigatran allows the use of routine coagulation assays for the diagnosis of hemostasis disorders. J Thromb Haemost 2015; 13: 2087-92.Summary. Background: The anticoagulant effect of dabigatran can be approximated by its prolongation of routine coagulation assays. Consequently, dabigatran also interferes with thrombophilia screening or with diagnosing hemostasis disorders that have developed after the initiation of anticoagulant treatment, such as vitamin K deficiency or acquired hemophilia A. Objectives: This study was carried out to determine whether idarucizumab, a humanized antibody fragment that binds dabigatran, could fully neutralize dabigatran in routine diagnostic coagulation assays conducted in vitro, thereby preventing false-positive or false-negative diagnostic readouts. Methods: Preliminary experiments identified coagulation assays that were sensitive to dabigatran, and identified a concentration of idarucizumab that neutralized the effects of dabigatran. These assays were then carried out with patient and control plasma samples spiked with dabigatran, with or without a molar excess of idarucizumab. Results: Dabigatran altered the prothrombin time, activated partial thromboplastin time and thrombin time, and the measurement of intrinsic and extrinsic factor levels. Screening and confirmation tests used for lupus anticoagulant detection were prolonged by dabigatran, falsely suggesting the presence of lupus anticoagulant. Conversely, the addition of dabigatran falsely corrected an abnormal activated protein C resistance ratio. Addition of idarucizumab completely normalized these measurements, and allowed the correct identification of normal and abnormal samples with these assays. Conclusions: In vitro addition of idarucizumab to plasma samples containing dabigatran fully neutralizes the drug, and facilitates the use of routine coagulation assays to allow the diagnosis of hemostasis disorders that may be concurrently present in patients taking dabigatran.

Examination of the amplitude of coagulation curves generated during TT tests may provide additional information to enable the differential diagnoses of diseases following a low fibrinogen measurement by the Clauss method.

The RAFLS is a suitable calibrator for one-stage FVIII assays carried out with F8DP containing VWF. However, calibration with the RAFLS does not avoid the effect of patient-specific variables that contribute to discrepancies between the measurements of ReFacto AF levels with one-stage and chromogenic FVIII assays.

Introduction The monitoring of factor VIII (FVIII) replacement therapy relies on the accurate measurement of FVIII activity over a large concentration range. However, unexplained overestimation of low FVIII levels has recently been reported with extended half‐life recombinant FVIIIs. Aim The objective of this study was to confirm previous publications indicating that the reagents used to generate the calibration curves determine the accuracy of the measurement of low FVIII levels. Methods We generated FVIII calibration curves with FVIII‐deficient plasmas or a commercial diluent buffer. We then measured FVIII levels in FVIII‐deficient plasma spiked with plasma FVIII, a full‐length recombinant FVIII (Advate®, Shire, Brussels, Belgium) and two extended half‐life recombinant FVIIIs (Elocta® , Swedish Orphan Biovitrum, Woluwe Saint‐Lambert, Belgium and Afstyla®, CSL Behring, Mechelen, Belgium). FVIII levels were also analyzed in spiked samples prediluted two‐ and fourfold, either in diluent buffer or in FVIII‐deficient plasma to evaluate parallelism. Results Coagulation times of calibration curves generated with diluent buffer were longer than those with FVIII‐deficient plasmas. This resulted in an overestimation of FVIII levels lower than 25 IU/dL in spiked samples and in detection of FVIII activity (≥1 IU/dL) in FVIII‐deficient plasma. Predilution of samples with diluent buffer rather than with FVIII‐deficient plasma also led to discordant results. Conclusion Our data confirm that the generation of calibration curves by dilution in FVIII‐deficient plasma is crucial for the accurate measurement of low FVIII levels. When serial dilutions of samples are analyzed, predilution in FVIII‐deficient plasma is required to respect the parallelism criteria. These methods should be more generally implemented for coagulation instruments.