Antibodies against cyclic citrullinated peptide (CCP) and levels of cartilage oligomeric matrix protein (COMP) in very early arthritis:: relation to diagnosis and disease activity

Objective: To measure serum levels of antibodies against cyclic citrullinated peptide (anti-CCP antibodies) and serum cartilage oligomeric matrix protein (COMP) in patients with early joint inflammation, and to study the correlation of these two tests with clinical measurements. Methods: Adult patients with recent-onset arthritis, of <3 months' duration, were referred from primary healthcare centres to rheumatologists. Serum levels of anti-CCP antibodies and COMP at baseline were analysed by enzyme immunoassay (EIA) and compared with clinical baseline data. Results: Sixty-nine patients were included. The specificity of the anti-CCP antibody test for RA was 96%, and the sensitivity was 44%. There was a significant difference between the four diagnosis groups in the anti-CCP antibody test, probability (p) < 0.001, whereas no significant differences were found concerning COMP. The baseline serum COMP test correlated with age (p = 0.0001), joint score for swollen joints (p = 0.02), and C-reactive protein (CRP) (p = 0.02). Conclusion: This study confirms the high diagnostic specificity of anti-CCP antibodies for rheumatoid arthritis (RA) in a prospective population-based study of very early arthritis. Raised serum COMP levels were common in all diagnosis groups in this series, indicating cartilage involvement in both self-limiting and non-erosive disease.