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Several randomized controlled trials have investigated the use of direct oral anticoagulants in patients with thrombotic antiphospholipid syndrome.

Several randomized controlled trials have investigated the use of direct oral anticoagulants in patients with thrombotic antiphospholipid syndrome. One randomized controlled trial of 116 patients with antiphospholipid syndrome (28% triple positive) compared rivaroxaban with the vitamin K antagonist warfarin.207 While the study did not meet its primary endpoint (change in endogenous thrombin potential), no thrombosis or major bleeding was observed in either group over seven months.207 Another trial evaluated rivaroxaban compared with warfarin in 120 triple positive patients with antiphospholipid syndrome.208 The composite primary outcome of thrombotic events, major bleeding, and vascular mortality was higher in the rivaroxaban group (hazard ratio 7.4, 95% confidence interval 1.7 to 32.9).208 A second study also failed to show non-inferiority of rivaroxaban compared with warfarin as a secondary thromboprophylaxis agent.209 Finally, a randomized controlled trial of apixaban versus warfarin was stopped early after the primary outcome, stroke, occurred in six of 23 patients randomized to apixaban (albeit three receiving prophylactic rather than therapeutic dosing), as compared with 0 of 25 patients randomized to warfarin.210 A recent meta-analysis found no evidence of a higher risk of recurrent venous thromboembolism in patients with antiphospholipid syndrome treated with direct oral anticoagulants compared with those treated with warfarin211; this was in contrast to a significantly increased risk of recurrent arterial thrombosis.211 Moreover, risk of recurrent arterial thrombosis tended to be more frequent in patients with a history of arterial thrombosis.211 These results are in line with international guidelines which recommend not to use direct oral anticoagulants in patients with antiphospholipid syndrome with a history of arterial thrombosis, but raise the question of the efficacy of direct oral anticoagulants to prevent venous thrombosis in a subset of patients with antiphospholipid syndrome.198212 At present, our opinion is that direct oral anticoagulants should be avoided when possible in patients with a history of arterial thrombosis or with triple positive antiphospholipid syndrome, regardless of whether the initial thromboembolic event was venous or arterial, pending further well designed clinical trials.