Comparison of tests for the lupus anticoagulant and antiphospholipid antibodies in systemic lupus erythematosus.

A variety of laboratory assays are used to screen for the presence of the lupus anticoagulant. Six commonly used coagulation tests, and the ELISA assay for antiphospholipid antibody using three different substrate phospholipids, have been evaluated in 110 patients with systemic lupus erythematosus or lupus-like disease. One or more coagulation assays was abnormal in 41% (45/110) of the patients. No individual test detected more than 78% of these abnormalities, indicating that a single phospholipid based coagulation test cannot be used to screen for a possible lupus anticoagulant. A combination of Actin FSL, DTTA and DRVVT detected all the abnormalities. The most sensitive two-test combination was Actin FSL and DRVVT. Approximately half (56%) of the patients with a positive clotting test had an abnormal antiphospholipid antibody assay. A similar proportion (58%) of the aPL positive patients had a prolonged coagulation test. The marked discordance between the coagulation assays and a positive antiphospholipid antibody test further complicates the laboratory definition of this abnormality, at least in patients with systemic lupus erythematosus.