RESUMO
OBJECTIVE: To evaluate the dependence on the serum cofactor of anticardiolipin antibodies (aCL) in infectious and autoimmune diseases. We also studied their correlation with some clinical manifestations, specially thrombosis. METHODS: aCL were determined with a standard ELISA method, and a modified ELISA in which we substituted bovine serum albumin (BSA), gelatin and skim milk powder for fetal calf serum (FCS). Categorized variables were analyzed by means of the chi 2 test and Fisher's test. Four groups of patients were studied. Group 1. Patients with aCL and autoimmune disease (systemic lupus erythematosus [SLE] and the primary antiphospholipid syndrome [PAPS]). Group 2. Patients with aCL, no symptoms and no underlying infection or autoimmune disease. Group 3. Patients with aCL and infectious diseases (syphilis, leprosy, HIV infection and Q fever). Group 4. Control group. RESULTS: (a) 19 of 20 samples from patients in Group 1 disclosed cofactor dependence in aCL activity. (b) 17 of 19 samples from patients in Group 3 had aCL activity, that was independent of the presence of the cofactor. (c) 3 of 4 patients in Group 2 had cofactor independent aCL and one had cofactor dependent aCL activity. (d) no control group patient had aCL. (e) association of cofactor dependent aCL with the development of clinical manifestations (thrombosis) was statistically significant (p < 0.0001). (g) cofactor dependent aCL and cofactor independent aCL were, respectively, associated with autoimmune and infectious diseases (p < 0.0001). CONCLUSIONS: (a) Dependence or independence of the cofactor helps to differentiate "infectious" aCL from "autoimmune" aCL. (2) aCL related clinical manifestations (thrombosis) depends on the presence of cofactor dependent aCL and not on cofactor independent aCL.