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

To examine the effects of patients taking the direct blood coagulation factor Xa inhibitor rivaroxaban on lupus anticoagulant testing results in a clinical setting.

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.

The average dilute Russell viper venom time (DRVVT) and normal plasma-mix screening results to confirmation ratios in rivaroxaban-naïve 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.

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.