[The specificity of anti-cyclic citrullinated peptide antibodies in the diagnosis of rheumatoid arthritis from a large cohort study in the Chinese].

OBJECTIVE To determine the sensitivity and specificity of anti-cyclic citrullinated peptide antibodies (anti-CCP antibodies) in the diagnosis of rheumatoid arthritis. METHOD A total of 1018 healthy donors, 212 patients with rheumatoid arthritis, 435 patients with other connective tissue disease were recruited to this study. Anti-CCP antibodies and IgM-rheumatoid factor (RF) were determined by ELISA according to manufacturer instructions, with a cut-off of 20U. RESULT The frequency of positive anti-CCP antibodies in patients with rheumatoid arthritis is 48.1% (n = 102), higher than healthy donors (2.6%, n = 26) and patients with other connective tissue diseases (3.7%, n = 16). The specificity of anti-CCP antibodies is 97.4%. The titer of anti-CCP antibodies in patients with rheumatoid arthritis (429.7 U) is much higher than that in healthy donors (29.3 U) and patients with other connective tissue diseases (36.5 U). The frequency of positive IgM-RF in patients with rheumatoid arthritis is 94.3% whilst only 21.5% in healthy donors. The false positivity rate of IgM-RF is higher than anti-CCP antibody. CONCLUSION Anti-CCP antibodies is a highly specific autoantibody in the diagnosis of rheumatoid arthritis.