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

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Abstract

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-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.

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.

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