Anticardiolipin antibodies in clinical conditions associated with a risk of thrombotic events

Anticardiolipin antibodies (ACAs) of IgA, IgG, and IgM isotypes were measured using an enzyme-linked immunosorbent assay (ELISA) in patients with SLE, and in other groups of subjects with a higher or lower risk of developing thrombosis. IgA ACAs were present in high titers in all groups and had little discriminant value in predicting thrombotic risk. In patients without the lupus anticoagulant (LAC) with conditions in which a thrombotic tendency was a feature (primigravidae with preeclampsia or intrauterine growth retardation, patients with angina or acute myocardial infarction, those on anticoagulant therapy for apparently spontaneous thrombosis, and patients with Behcet's syndrome in whom there was a history of thrombosis) ACAs of all isotypes were present in 44/191 (23%). In patients in whom a thrombotic tendency was not a feature (normal controls, primigravidae with normal deliveries, patients with rheumatoid arthritis, and with Behcet's syndrome in whom there was no thrombotic history) 22/241 (9%) had ACAs. Although ACAs were more likely to be present in a subset of patients without systemic lupus erythematosus (SLE) and/or the LAC, their presence was a poor discriminator of increased risk of thrombosis.