Effectiveness and safety of the direct oral anticoagulants in non-triple positive antiphospholipid syndrome without prior arterial thromboembolism

Thrombotic antiphospholipid syndrome (TAPS) is an autoimmune disorder that manifests with venous thromboembolism (VTE) and/or arterial thromboembolism (ATE) in the presence of persistent antiphospholipid antibodies (aPLs). Recent trials have failed to demonstrate non-inferiority of the direct oral anticoagulants (DOACs) compared to vitamin K antagonists as anticoagulation in TAPS, but there is a subgroup of non-triple positive patients without prior ATE in who only limited data exists. The objective of this study was to assess the effectiveness and safety of DOACs in non-triple positive TAPS without prior ATE. We conducted a retrospective review of all non-triple positive TAPS patients without prior ATE who were anticoagulated with a DOAC at two tertiary care hospitals from January 2010 to July 2020. We assessed outcomes of VTE, ATE, major bleeding, and clinically relevant non-major bleeding (CRNMB). 50 patients were included in the analysis, encompassing 157.2 years of patient follow-up. There were no recurrent VTE, but one patient had a possible arterial thrombosis (0.64 events per 100 patient-years [95% confidence interval (CI 0.16-35.49)] as a transient ischemic attack (TIA) which occurred on reduced dose DOAC. There were no major bleeding events, but two patients had CRNMB (1.27 events per 100 patient-years [95% CI 1.5-46.0]), both as menorrhagia. DOACs were effective and safe as anticoagulation in non-triple positive TAPS patients without prior ATE with a low rate of recurrent thrombosis and bleeding. Larger, prospective controlled studies are required to confirm these findings prior to routine use of DOACs in this subgroup.