Increased serum concentrations of cartilage oligomeric matrix protein. A prognostic marker in early rheumatoid arthritis.

Two cartilage specific macromolecules, cartilage oligomeric matrix protein (COMP) and proteoglycan, were quantified by immunoassay in sera of two groups of patients with rheumatoid arthritis (RA) of recent onset to evaluate the prognostic value of such measurements. Patients with rapidly progressive joint destruction had increased COMP concentrations initially, which subsequently decreased. A group with more benign disease, and less extensive joint damage, had normal COMP levels throughout the study period. Serum concentrations of proteoglycan were normal in both groups. Thus measurement of COMP in serum early in the course of RA holds promise as a prognostic marker for development of joint destruction in this disease.