Assays for lupus anticoagulant: the sensitivity of different assays

Fifty patients with systemic lupus erythematosus were studied for the presence of lupus anticoagulant using three different assays--kaolin clotting time, platelet neutralization test, and tissue thromboplastin inhibition test. Lupus anticoagulant could be detected in seven cases (14%) with the use of one test in cases with a partial prothrombin time with kaolin more than five seconds greater than normal. The detection rate rose to 20% (10 cases) when using all three tests, so a panel of three assays could identify lupus patients apparently at risk for thrombotic complications.