Abstract

Abstract Objective To define the antiphospholipid score (aPL‐S) by testing multiple antiphospholipid antibodies (aPL) and to evaluate its efficacy for the diagnosis of antiphospholipid syndrome (APS) and predictive value for thrombosis. Methods This study comprised 2 independent sets of patients with autoimmune diseases. In the first set of patients (n = 233), the aPL profiles were analyzed. Five clotting assays for testing lupus anticoagulant and 6 enzyme‐linked immunosorbent assays (IgG/IgM anticardiolipin antibodies, IgG/IgM anti–β 2 ‐glycoprotein I, and IgG/IgM phosphatidylserine‐dependent antiprothrombin antibodies) were included. The association of the aPL‐S with a history of thrombosis/pregnancy morbidity was assessed. In the second set of patients (n = 411), the predictive value of the aPL‐S for thrombosis was evaluated retrospectively. Two hundred ninety‐six of these patients were followed up for >2 years. The relationship between the aPL‐S and the risk of developing thrombosis was analyzed. Results In the first set of patients, the aPL‐S was higher in those with thrombosis/pregnancy morbidity than in those without manifestations of APS ( P < 0.00001). For the aPL‐S, the area under the receiver operating characteristic curve value was 0.752. In the second set of patients, new thromboses developed in 32 patients. The odds ratio (OR) for thrombosis in patients with an aPL‐S of ≥30 was 5.27 (95% confidence interval [95% CI] 2.32–11.95, P < 0.0001). By multivariate analysis, an aPL‐S of ≥30 appeared to be an independent risk factor for thrombosis (hazard ratio 3.144 [95% CI 1.383–7.150], P = 0.006). Conclusion The aPL‐S is a useful quantitative index for diagnosing APS and may be a predictive marker for thrombosis in autoimmune diseases.