LUPUS ANTICOAGULANT IS THE STRONGEST RISK FACTOR FOR BOTH VENOUS AND ARTERIAL THROMBOSIS IN PATIENTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS - COMPARISON BETWEEN DIFFERENT ASSAYS FOR THE DETECTION OF ANTIPHOSPHOLIPID ANTIBODIES

Antiphospholipid antibodies (aPL) characterize patients at risk for bo th arterial and venous thrombotic complications. Recently it has been recognized that the presence of plasma proteins such as beta(2)-glycop rotein I (beta 2GPI) and prothrombin are essential for the binding of aPL to phospholipids and that these proteins are probably the real tar get of aPL. The discovery of these new antigens for aPL introduces the possibility of new assays to detect the presence of aPL. However, it is not known whether these assays improve the identification of patien ts al risk for thrombosis. In this retrospective study we compared the value of the classic assays LAC (lupus anticoagulant) and ACA (antica rdiolipin antibodies) to detect aPL associated with thrombotic complic ations, with new assays which are based on the binding of aPL to the p lasma proteins prothrombin and beta 2GPI. To do so, we have used these assays in a group of 175 SLE patients and correlated the positivity o f the different assays with the presence of a history of venous and ar terial thrombosis. Control groups were patients without SLE but with L AC and/or ACA and thrombosis (n = 23), patients with thrombosis withou t LAC and ACA (n = 40) and 42 healthy controls. In the univariate anal ysis, in which no distinction has been made between high and low antib ody levels: we confirmed LAC and ACA to be related to both arterial an d venous thrombosis. Anti-beta 2GPI- and anti-prothrombin-antibodies, both IgG and IgM correlate with venous thrombosis and anti-beta 2GPI-I gM with arterial thrombosis. Multivariate analysis showed that LAC is the strongest risk factor (OR 9.77; 95%CI 1.74-31.15) for arterial thr ombosis. None of the other factors is a significant additional risk fa ctor. For venous thrombosis LAC is the strongest risk factor (OR 6.55; 95% CI 2.36-18.17), but ACA-IgM above 20 MPL units also appeared to b e a significant (p = 0.0159) risk factor (OR 3.90; 95% CI 1.29-11.80). Furthermore, the presence of anti-beta 2GPI- and/or anti-prothrombin- antibodies in LAC positive patients (n = 60) does not increase the ris k for thrombosis, The results showed that (i) the LAC assay correlates best with a history of both arterial and venous thrombosis and (ii) n either the anti-beta 2GPI ELISA nor the anti-prothrombin ELISA gives a dditional information for a thrombotic risk in SLE patients.