Rivaroxaban Therapy, False-Positive Lupus Anticoagulant Screening Results, and Confirmatory Assay Results

Objective: To examine the effects of patients taking the direct blood coagulation factor Xa inhibitor rivaroxaban on lupus anticoagulant testing results in a clinical setting. Methods: We reviewed the results of lupus anticoagulant testing performed over a 2-year period. Of 59 patients who met criteria for a lupus anticoagulant, 18 were taking rivaroxaban. We reviewed and compared the parameters of lupus anticoagulant testing. Results: The average dilute Russell viper venom time (DRVVT) and normal plasma-mix screening results to confirmation ratios in rivaroxaban-naive patients were 1.6 and 1.7, respectively. In the rivaroxaban group, the same parameters were 1.7 and 1.6, respectively (P = -0.28 and 0.46, respectively). For 15 of 18 patients taking rivaroxaban, results were corrected on the confirmation steps of both tests. Conclusions: Rivaroxaban confounds lupus anticoagulant testing because the DRVVT is prolonged in these patients but it also corrects with excess phospholipid, mimicking a lupus anticoagulant. Patient medication review is critical to avoid false-positive findings and inappropriate diagnosis of antiphospholipid syndrome.