Antiphospholipid antibody profiles and their clinical associations in Chinese patients with systemic lupus erythematosus

Objective. Different prevalences of antiphospholipid antibodies (aPL) have been reported in different populations of patients with systemic lupus erythematosus (SLE). Chinese are generally believed to have lower risk of vascular thrombosis. We examined the prevalence of aPL including lupus anticoagulant (LAC), anticardiolipin (aCL) and anti-β₂- glycoprotein I (anti-β₂-GPI) antibodies, the level of thrombotic risk, and the association of aPL with thrombotic and pregnancy outcomes in a Chinese cohort with SLE at the university lupus clinic during the period 1986-2003. Methods. aPL were measured in 272 SLE patients, and medical records were reviewed for vascular thrombosis and pregnancy outcomes. Results. The prevalence of LAC, IgG aCL, and IgG anti-β₂-GPI antibodies was 22.4%, 29.0%, and 7.7%, respectively. There were 38 episodes of thrombosis after a mean duration of followup of 11.0 ± 6.8 SD years, giving a thrombotic rate of 1.26/100 patient-years. All aPL were shown to be associated with vascular thrombosis. IgG anti-β₂-GPI antibodies were found to be associated with recurrent thrombosis [8.0/100 patient-years or 25.0% (7/28)]. Patients taking hydroxychloroquine were found to have fewer thrombotic complications than those who were not (OR 0.17, 95% CI 0.07-0.44; p <0.0001). LAC was the strongest factor associated with recurrent miscarriages [relative risk 12.3, 95% CI 1.22-123.31; p = 0.03). The diagnosis of secondary antiphospholipid syndrome was satisfied in 8.9% of patients. Conclusion. The lifetime and recurrent thrombotic rates in our patients with aPL were not particularly different from those in the literature. However, the lower prevalence of aPL in our cohort may suggest a role of other prothrombotic factors in predisposition to thrombosis.