Elevated partial antiphospholipid score is a strong risk factor for thrombosis in patients with systemic lupus erythematosus: a validation study

This study aims to identify risk factors for thrombosis in patients with systemic lupus erythematosus (SLE) and to validate the efficacy of the partial antiphospholipid (aPL) score for thrombosis prediction and diagnosis of antiphospholipid syndrome (APS). This study included 325 SLE patients, 188 of whom completed a follow-up of 31.01 months (range 23–48 months). Partial aPL score was calculated by adding up the individual scores for activated partial thromboplastin time (APTT), lupus anticoagulant, IgG/IgM anticardiolipin antibodies (aCL), and IgG/IgM anti-β2-glycoprotein I (anti-β2GPI). A simplified aPL score was developed using only APTT, IgG/IgM aCL, and IgG/IgM anti-β2GPI. Partial aPL scores were significantly higher in SLE patients with thrombosis (p < 0.0001). A history of thrombosis (p < 0.0001), a partial aPL score >10 (p < 0.0001), and immunosuppressant use (p = 0.012) were independent risk factors for thrombosis. For patients with a history of thrombosis, partial aPL score was the strongest risk factor for recurrent thrombosis (p < 0.0001, odds ratio = 30.34 (95 % CI 7.70–118.81)). For APS diagnosis, the area under the receiver-operating characteristic curve (AUC) was 0.809 (95 % CI 0.73–0.89) using the partial aPL score. Similarly, the simplified aPL score was significantly associated with thrombosis (p < 0.0001) and was acceptable for APS diagnosis (AUC 0.797, 95 % CI 0.72–0.88). An elevated partial aPL score is a strong risk factor for thrombosis in SLE patients and is a useful tool to predict recurrent thrombosis. Partial aPL score and simplified aPL score, although comprising fewer items than the original aPL score, also represent valuable quantitative indices for APS diagnosis.