Serum levels of cartilage oligomeric matrix protein - A predicting factor and a valuable parameter for disease management in rheumatoid arthritis

Objective: To examine whether cartilage oligomeric matrix protein (COMP) correlates with inflammation and/or joint destruction of patients with rheumatoid arthritis (RA) and to test COMP as predicting factor for the outcome of patients with established RA. Methods: Serum levels of COMP were measured in sera of 62 patients, suffering from RA according to the ACR criteria and treated in intervals in our department, over a period of 5 years. A commercially available sandwich-type ELISA-kit developed by AnaMar Medical AB, Sweden, was used. The results of serum COMP were compared with the Disease Activity Score (DAS), the Larsen Score, and clinical and laboratory parameters. Results: We found a positive correlation between serum levels of COMP at baseline and deterioration of Larsen score even after 5 years (p<0.007; r=0.34). To confirm serum COMP as an independent predicting factor for patients with RA we looked at a subgroup of patients (n=17) with elevated serum levels of COMP (mean 11,7 U/l) and low clinical prognostic factors. In this subgroup we also found a significant correlation with delta Larsen score (p<0.01; r=0.59) after 5 years. Conclusion: Serum levels of COMP is known to reflect increased cartilage turnover. The results indicate that serum COMP may be used as a prognostic marker of cartilage degradation in a patient group with established RA.