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.
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.
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).
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.