The lupus inhibitor in thromboembolic disease and intrauterine death in the absence of systemic lupus.

This study describes the use of a modified dilute thromboplastin assay for demonstration of the lupus coagulation inhibitor in plasma. A one-stage clotting inhibition assay is used in which the ability of the test plasma to prolong the clotting time of normal plasma is measured. The method is easy to perform and suitable for routine use. Clinical and laboratory data from five patients with the inhibitor but without systemic lupus erythematosus are presented. Thromboembolic manifestations were observed in three patients and obstetric complications possibly due to placenta thrombosis in two. One patient showed a bleeding tendency, associated with prothrombin deficiency. A number of pathological coagulation analyses and other laboratory data may be due to affinity of the lupus inhibitor for negatively charged phospholipids in vitro.