Efficacy and safety of low-dose acetylsalicylic acid for the prevention of thromboembolic events in individuals positive for antiphospholipid antibodies: A systematic review and meta-analysis

Background: Anti-Phospholipid Antibodies (aPL) are autoantibodies predisposing to an increased risk of thrombotic events. The net clinical benefit of antithrombotic prophylaxis in aPL carriers is still unclear. We performed a systematic review to assess the efficacy and safety of antiplatelet drugs for the primary prevention of thrombotic events in aPL carriers. Methods: Studies were identified by electronic search of MEDLINE and EMBASE database until May 2023. The differences in the outcomes among groups were estimated as pooled odds ratio (OR) and corresponding 95 % confidence interval (CI). Statistical heterogeneity was evaluated using the I2 statistic. Results: 1056 participants were included in 10 studies, 2 RCTs and 8 cohorts. Low-dose acetylsalicylic acid (LDA) was the antiplatelet drug in treated patients. Thrombotic events were significantly reduced in the LDA group compared to the control group [OR 0.46 (95 % CI 0.30-0.71), I2 27%, fixed-effects model]. Arterial thrombotic events were significantly reduced in the LDA group compared to the control group [OR 0.47 (95 % CI 0.26-0.86), I2 0%, fixed-effects model]. Venous thrombotic events were significantly reduced in the LDA group compared to the control group [OR 0.44 (95 % CI 0.21-0.89, I2 1%, fixed-effects model]. No major bleedings occurred in the five studies reporting them. Conclusions: aPL carriers receiving long-term LDA had a significant reduction of thrombotic events, without a significant increase of the risk of major bleeding. It remains unclear if LDA has the same benefit/risk profile in all aPL profile, i.e. single, double, or triple positivity.