THE PREVALENCE AND CLINICAL ASSOCIATIONS OF ANTICARDIOLIPIN ANTIBODIES IN A LARGE INCEPTION COHORT OF PATIENTS WITH CONNECTIVE-TISSUE DISEASES

PURPOSE: TO determine the prevalence and clinical associations of anti cardiolipin antibodies (aCL) in a blinded, controlled study of patient s with a variety of connective tissue diseases (CTD) using a standardi zed aCL testing system. PATIENTS AND METHODS: Anticardiolipin antibodi es (IgG, IgM, and IgA) were measured by direct enzyme-linked immunosor bent assay (ELISA) in the baseline serum samples of patients enrolled in a Cooperative Study of Systematic Rheumatic Diseases (CSSRD), Natio nal Institutes of Health (NIH) supported, 5-year inception-cohort, pro spective study of early rheumatic diseases: rheumatoid arthritis (RA, n = 70), systemic lupus erythematosus (SLE, n = 70), scleroderma (PSS, n = 45), myositis (PM/DM, n = 36), and early undifferentiated connect ive tissue disease (EUCTD, n = 165). Diagnosis was based on standardiz ed criteria and determined at the last study visit. A nested group of patients with Sjogren's syndrome (SJ, n = 44) was also defined. Serum from 200 blood donors (BE) served as controls. Additional patients wit h known antiphospholipid syndrome (APS, n = 33) and ANCA-related renal vasculitis (ANCA, n = 52) were also studied. Laboratory personnel wer e blinded to sample diagnostic group. RESULTS: The prevalence of eithe r IgG or IgM aCL among each diagnostic group was RA 15.7%, SLE 15.76%, PSS 6.7%, PM/DM 8.3%, EUCTD 9.1%, SJ 6.8%, ANCA 3.8%, and BE controls 4.0%. Prevalence of aCL was significantly different for both the RA a nd SLE groups versus BE controls (P < 0.01) but not among other diagno stic groups. Only 2 study patients had positive tests for IgA aCL (1 w ith PM/DM and 1 with EUCTD) versus 15% of APS with positive IgA aCL. S tudy patients positive for IgG or IgM aCL were significantly more like ly to have hemolytic anemia or a positive serologic test for syphilis and less likely to have Raynaud's phenomenon. However, no associations were found between aCL positivity and thrombocytopenia, seizures, ren al insufficiency, presence of a positive antinuclear antibody or rheum atoid factor, subcutaneous nodules or digital ulcers. CONCLUSIONS: Bas ed on results from this large CSSRD inception cohort, anticardiolipin antibodies are present in approximately 16% of patients with RA or SLE but are less common in patients with PSS, PM/DM, EUCTD, SJ, and ANCA vasculitis, where their prevalence approaches that in the normal popul ation. Few consistent clinical associations can be found among patient s with CTD who are aCL positive. The complete diagnostic and prognosti c importance and specificity of these antibodies remains to be fully d etermined. (C) 1996 by Excerpta Medica, Inc.