Lupus anticoagulant and anticardiolipin antibodies in systemic lupus erythematosus

Lupus anticoagulant and anticardiolipin antibodies are antiphospholipid antibodies which have been independently associated with a high incidence of thrombotic diseases. However, the importance of their combined occurrence has not yet been examined.

We investigated 70 patients with systemic lupus erythematosus for the presence of anticardiolipin antibodies paying particular attention to a history of thrombosis and abortion. Lupus anticoagulant was detected using the kaolin clotting time, its mixing tests with normal plasma and the inosithin neutralization test. Anticardiolipin antibodies were detected using the ELISA technique.

Lupus anticoagulant was detected in 11 patients (16%) and anticardiolipin antibodies in 13 (19%). Six patients were positive for both lupus anticoagulant and anticardiolipin antibodies. These patients had a higher incidence of thrombosis or recurrent abortion (5 of 6) compared to those with lupus anticoagulant (2 of 5) or anticardiolipin antibodies alone (1 of 7). The amount of inosithin required to neutralize lupus anticoagulant was greater [mean (SD) 27.5 (20.5) micrograms] in patients with both lupus anticoagulant and anticardiolipin antibodies than in patients with lupus anticoagulant alone [mean (SD) 4.0 (5.4) micrograms].

The presence of lupus anticoagulant is associated with thrombosis and recurrent abortion which are more frequent when both lupus anticoagulant and anticardiolipin antibodies are present and these patients probably have more severe disease as the amount of inosithin required to neutralize the lupus anticoagulant was greater.