The prevalence and clinical associations of the lupus anticoagulant in systemic lupus erythematosus.

To determine the prevalence and clinical associations of the lupus anticoagulant (LAC) in patients with systemic lupus erythematosus (SLE), we studied 74 patients with SLE, 6 with lupus-like disease and a heterogeneous group of 45 patients with various autoimmune diseases. LAC was demonstrated in 19 SLE patients (26%), 5 patients with lupus-like disease (83%) and in none of the other patients. Statistically significant associations were found between LAC and a history of thromboembolic events (p less than 0.001), fetal loss (p less than 0.001), thrombocytopenia (p less than 0.01), biologically false-positive VDRL test (p less than 0.02) and convulsions (p less than 0.05). A negative correlation was found between LAC and a history of butterfly rash (p less than 0.01) and the presence of antibodies against extractable nuclear antigen (p less than 0.01). No significant difference was found between LAC-negative SLE patients and patients with other autoimmune diseases with respect to the prevalence of thromboembolic events or fetal loss. We conclude that LAC is a useful marker to identify a subset of patients with SLE or lupus-like disease at risk of thromboembolic events, fetal wastage, and thrombocytopenia.