Thrombotic Risk Factors In Primary Antiphospholipid Syndrome

Abstract

Background and Purpose— Because thromboembolic events are frequently observed in primary antiphospholipid syndrome (PAPS), we assessed the risk factors for new thrombotic episodes. Methods— Fifty-six PAPS patients (mean age, 37±10 years) were prospectively studied for 5 years. The preliminary Sapporo classification criteria for antiphospholipid syndrome (APS; a medium–high anticardiolipin antibody [aCL] titer and/or a positive lupus anticoagulant [LA] test in the presence of vascular thrombosis and/or pregnancy morbidity) were used to confirm the diagnosis. Thrombotic episodes or pregnancy losses before a diagnosis of PAPS were considered events, and any new disease manifestation other than thrombocytopenia was considered a recurrent event. Only patients with objectively verified thrombotic events were included in the study. Results— Twenty-one new thrombotic events were observed in 15 subjects (26.8%), including 3 (5.4%) who died during the follow-up. The patients with IgG aCL levels of >40 IgG phospholipid unit (GPL-U) showed a higher incidence of new thrombotic events (43.3%) than those with levels of ≤40 GPL-U (7.7%). Univariate analysis identified a history of recurrent clinical events ( P =0.004), a highly positive aCL titer ( P =0.007), and the presence of cardiac abnormalities ( P =0.036) as significant risk factors for new thrombotic events. A multivariate regression model confirmed that an IgG aCL titer of >40 GPL-U was an independent risk factor for thrombosis (odds ratio, 9.17; 95% confidence interval, 1.83 to 46.05). Conclusions— A high IgG aCL titer is the strongest predictor of new thrombotic events in PAPS patients.