Anticardiolipin and anti-beta2GPI antibodies in a large series of European patients with systemic lupus erythematosus. Prevalence and clinical associations. European Concerted Action on the Immunogenetics of SLE.

OBJECTIVE: To test the prevalences and the clinical associations of anticardiolipin (aCL) and anti-beta2GPI (abeta2GPI) antibodies in a large series of European patients with systemic lupus erythematosus (SLE).
METHODS: 574 SLE patients from 7 European countries were tested for aCL and abeta2GPI by ELISA methods.
RESULTS: aCL of IgG, IgM, and IgA isotypes were detected in 22.8%, 14%, and 13.9% of the patients, respectively. IgG and IgM abeta2GPI were detected in 20% of the patients. The presence of aCL was highly associated with the presence of abeta2GPI. Medium-high titer IgG aCL and abeta2GPI were associated with thrombosis, with similar sensitivity, specificity, and positive predictive value. When present at medium-high titer, IgG aCL were associated with thrombocytopenia, IgM aCL with hemolytic anemia, and cerebrovascular accidents. IgA aCL with livedo reticularis and Raynaud's phenomenon.
CONCLUSIONS: aCL, when present at medium-high titer, are as important as abeta2GPI, as a risk factor for thrombosis. Medium-high titer aCL, but not abeta2GPI, are associated with other clinical features of the antiphospholipid syndrome.