Anticardiolipin antibodies, free protein S levels and thrombosis: a surveyin a selected population of rheumatoid arthritis patients

Objective. To investigate plasma levels of natural anticoagulant proteins s uch as protein S, protein C and antithrombin III in a selected population o f patients with rheumatoid arthritis (RA) with and without anticardiolipin antibody (aCL) positivity, and to evaluate the possible relationships with an increased risk of thrombotic events in RA. Methods. A total of 184 female RA patients attending our Extra-Articular In volvement RA Clinic were evaluated for aCL levels, total and free protein S , protein C and antithrombin III concentrations, and for the occurrence of thrombotic events. Patients were grouped as aCL positive (n = 35) and aCL n egative (n = 149). Results. Higher rates of venous and/or arterial thromboses were diagnosed i n patients with RA compared to controls (P = 0.01). In particular, lower fr ee protein S levels were found in aCL-positive patients with RA compared to both aCL-negative patients and controls (P = 0.001). Functional assays for protein C, antithrombin III as well as total protein S levels were found t o be in the normal range in all patients and controls. Conclusion. The association observed between aCL positivity and decreased l evels of free protein S in RA patients may represent one of the risk factor s for thrombotic events.