Background and purpose: Antiphospholipid antibodies have been associated with ischemic stroke in some but not all studies.
Methods: We performed a population-based case-control study examining antiphospholipid antibodies (anticardiolipin antibodies and lupus anticoagulants) using stored frozen sera and plasma in 160 cases and 340 controls enrolled in the Stroke Prevention in Young Women study. We evaluated for the presence of anticardiolipin antibody (IgG, IgM, and IgA isotypes) by an enzyme-linked immunosorbent assay and for the lupus anticoagulant using several phospholipid-dependent coagulation tests (activated partial thromboplastin time, dilute Russell's viper venom time) with mixing studies. If mixing studies were prolonged, confirmatory tests were performed.
Results: A positive anticardiolipin antibody level of any isotype was seen in 43 cases (26.9%) and 62 controls (18.2%) (P=0.03), lupus anticoagulant in 29 cases (20.9%) and 38 controls (12.8%) (P=0.03), and either anticardiolipin antibody or lupus anticoagulant in 61 cases (42.1%) and 86 controls (27.9%) (P=0.003). After adjustment for age, current cigarette smoking, hypertension, diabetes, angina, ethnicity, body mass index, and high-density lipoprotein levels, the relative odds of stroke for women with anticardiolipin antibody immunoreactivity of any isotype or a lupus anticoagulant was 1.87 (95% confidence interval, 1.24 to 2.83; P=0.0027).
Conclusions: The results from this study support the importance of antiphospholipid antibodies as an independent risk factor for stroke in young women.