Difficulties in diagnosing antiphospholipid syndrome in patients undergoing DOAC therapy

T. Flieder1, M. Weiser1, T. Eller2, M. Dittrich3, K. von Bargen1, F. Knüttgen1, A. Hohbein1, J. Kuhn1, C. Knabbe1, I. Birschmann1 (1Bad Oeynhausen, Germany, 2Bad Salzufflen, Germany, 3Würzburg, Germany)

Laboratory tests
Date: 17.02.2017,
Time: 17:15 - 18:15

Objective: It is well known that haemostaseologic laboratory assays are affected by the direct oral anticoagulants (DOACs) such as dabigatran, apixaban and rivaroxaban. This results in difficulties in diagnosing thrombophilia in patients who receive those drugs. The aim of our study was to show the effect on two different DRVVT assays and the lupus sensitive PTT in spiked samples from healthy volunteers and samples from patients receiving a DOAC.

Methods: Spiking experiments were performed using the original substances of the drugs and we used plasma concentrations of 0, 10, 30, 50 and 100 ng/mL. In order to evaluate the plasma levels of the drug we used ultra-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (Kuhn et al, 2015). The DRVVT assays we performed were from Instrumentation Laboratory (IL) and Stago, while the lupus sensitive PTT was from IL.

Results: All the DOACs showed pathological values in the DRVVT screen assays. In samples spiked with apixaban, no effect on the ratio of DRVVT assays could be observed whereas between 7 % and 11 % of samples from patients receiving apixaban showed pathological values. Up to 71 % of dabigatran spiked samples showed ratio values above the cut-off of 100 ng/mL drug concentration. By contrast, there was no effect detected in the patients’ samples. For rivaroxaban, the DRVVT assays were affected in both the spiked and patient samples.

Conclusion: We conclude that a LA/APS testing should be performed during a longer DOAC interruption if possible. Otherwise only the combination of DRVVT screen and DRVVT confirm is helpful before the next DOAC intake (trough level). However, positive results could indeed still turn out to be false positive.