The Effects of Indirect- and Direct-Acting Anticoagulants on Lupus Anticoagulant Assays: A Large, Retrospective Study at a Coagulation Reference Laboratory.

To investigate the effects of indirect- and direct-acting anticoagulants on the interpretation of lupus anticoagulant (LAC) assays.A retrospective database review was performed to identify all LAC panels from November 2012 to November 2015. The positivity rates for three LAC tests were compared among various anticoagulant medications.This analysis included 7,721 LAC panels. Direct oral anticoagulants, warfarin, and unfractionated heparin (UFH) were associated with higher LAC positivity rates compared with patients not receiving documented anticoagulation (83% for argatroban, 58% for dabigatran, 72% for rivaroxaban, 53% for apixaban, 56% for warfarin, and 36% for UFH vs 29% for no anticoagulation, P < .025). Direct thrombin inhibitors mainly affected the activated partial thromboplastin time-based assays and the tissue thromboplastin inhibition index (TTI), while direct factor Xa inhibitors mainly affected the TTI and the dilute Russell viper venom ratio.Results of LAC testing performed while patients are receiving anticoagulant therapies should be interpreted with caution to avoid misdiagnosing patients with the antiphospholipid syndrome and potentially committing them to long-term anticoagulation therapy.