Association of lupus anticoagulant and anticardiolipin antibodies with thrombosis in patients with systemic lupus erythematosus, primary antiphospholipid syndrome and other disorders.

Lupus anticoagulant (LA) and anticardiolipin antibodies (ACA) have been associated with thrombotic events and recurrent fetal loss. In order to assess the role of LA with the thrombotic tendency in various disease states we evaluated 38 patients with confirmed LA [tissue thromboplastin index (TTI) greater than 1.3; circulating anticoagulant index (CAI) greater than 15], subgrouped as follows: a) LA associated with systemic lupus erythematosus (SLE) (n = 13); b) primary antiphospholipid syndrome (PAPS) (n = 16); and c) LA associated with other disorders (n = 9). Male/female ratio differed between the groups: 0/13, 6/10 and 4/5, respectively. Venous and arterial thrombotic events were more common in the PAPS group (87%) compared with the SLE group (61%) and the other disorders group (22%). Serum ACA antiphospholipid IgG levels by ELISA were increased in the SLE and PAPS patients, but did not differ between the groups (167 +/- 24 vs. 190 +/- 28 mu respectively). Antiphospholipid IgM levels were higher in the SLE group compared with the PAPS group (127 +/- 15 vs. 67 +/- 16 mu). Mean TTI and CAI levels did not differ between the SLE, PAPS and other disorders groups (1.8 +/- 0.19, 2.8 +/- 0.9, 2.0 +/- 0.3 for TTI; 25 +/- 4, 33 +/- 4, 32 +/- 5 for CAI). Likewise TTI, CAI and ACA levels did not differ in patients with or without thrombosis. We conclude that the prevalence of thrombotic manifestations varies among patients with similar serum intensities of LA and levels of ACA, suggesting that other factors may be involved in the pathogenesis of thrombosis in these patients.