Thrombotic risk factors in patients with antiphospholipid syndrome: a single center experience

Patients with primary or secondary antiphospholipid syndrome (APS) have an increased risk of recurrent venous, arterial thrombosis and pregnancy complications. Therefore, determining thrombotic risk is important when individualizing antithrombotic therapy in patients with APS. To identify thrombotic risk factors in a cohort of APS patients. We conducted a retrospective review of APS patients who received care at a Hematology clinic of a university medical center from 2004 to 2017. Demographics, clinical features, antithrombotic therapy and thrombotic outcomes were collected. Time to event analysis identified clinical risk factors for thrombosis. The time varying effects of antithrombotic treatments on thrombosis outcome were analyzed. We identified 84 subjects with APS with a median age at diagnosis of 40.7 years [interquartile range [IQR] 33.5-57.6]. The majority were female (n = 63, 75%) and White (n = 45, 54%). Twenty-eight (33%) patients had concomitant autoimmune disease (AID) and of these, 15 (54%) had systemic lupus erythematosus. A thrombotic event occurred in 15 (18%) patients during a median follow-up of 48 months. A significantly higher rate of thrombotic events was observed in APS patients with AID compared to those without AID (hazard ratio (HR) 4.93, 95% CI 1.7-14.3, p = 0.04), and in black patients compared to whites (HR 5.94, 95% CI 1.1-32.1, p = 0.039). Patients on therapeutic anticoagulation regardless of type (warfarin, low molecular weight heparin or direct oral anticoagulants) were significantly less likely to have a recurrent thrombotic event compared to those on prophylactic anticoagulation (HR 0.11, 95% confidence interval [CI] 0.031-0.395, p = 0.001). However the numbers are too small to draw conclusions. Our study suggests that APS patients with concomitant AID and of Black race are at increased risk of recurrent thrombotic events.