Elevated Anticardiolipin Antibody Titer Is a Stroke Risk Factor in a Multiethnic Population Independent of Isotype or Degree of Positivity

Abstract

Background and Purpose —Previous studies have produced conflicting results regarding the putative association between anticardiolipin antibodies (aCL) and infarction in the general stroke population. These inconsistencies may be a function of sample size and methodological differences among the studies. The purpose of the present study, the largest case-control study of this issue to date, was to assess aCL status as an independent risk factor for ischemic stroke in a multiethnic, urban population. Methods —We obtained aCL titers in 524 hospitalized acute stroke patients and 1020 community controls enrolled in the Minorities Risk Factors and Stroke Study. The results were interpreted as negative (≤22.9 IgG phospholipid [GPL] or 10.9 IgM phospholipid [MPL] units), low positive (22.9 to 30.0 GPL or 10.9 to 15.0 MPL units), or high positive (>30.0 GPL or 15.0 MPL units). Odds ratios (ORs) were adjusted for age, sex, race/ethnicity, history of diabetes, hypertension, atrial fibrillation, coronary artery disease, and current cigarette smoking. Results —A positive aCL titer was present in 11% (111/1020) of controls and 34% (180/524) of cases. The adjusted OR for any positive aCL titer was 4.0 (95% CI, 3.0 to 5.5). For any positive IgG aCL titer this value was 3.9 (95% CI, 2.8 to 5.5), and for any positive IgM aCL titer it was 3.4 (95% CI, 2.1 to 5.5). There were no significant differences in ORs associated with high- or low-positive IgG or IgM aCL titers. Conclusions —In the largest study of its kind to date, aCL antibodies were demonstrated to be independent stroke risk factors across the 3 ethnic groups studied, conferring a 4-fold increased risk of ischemic stroke. IgG and for the first time IgM aCL were each shown to be associated with increased stroke risk. The prevalence of these antibodies and the stroke risk associated appear greater than previously reported.