Investigation of serum cartilage oligomer protein (COMP) levels in rheumatoid arthritis (RA)
KeywordsRheumatoid Arthritis Articular Cartilage ELISA Test Radiological Progression Seronegative Patient
RA is a disease characterised by an inflammatory process in the synovium and a degradation process of the joint cartilage. When articular cartilage matrix is degraded by a disease process, protein fragments are produced and some of them subsequently appear in the blood circulation and can be used to monitor cartilage degradation. COMP was first described by D.Heinegard as a noncollagenous protein primarily found in articular cartilage. COMP levels of serum and synovial fluids have been shown to have potential as prognostic markers of osteoarthritis and RA progression as well. For the detection of COMP mainly monoclonal antibody based competition ELISA systems have been described. Recently on the basis of the research group of D.Heinegard a two-site sandwich ELISA test from AnaMar Medical AB has been available in wich two monoclonal antibodies directed against separate antigenic determinant of COMP molecule are applied.
Using the COMP ELISA test of 'AnaMar' we measured the serum COMP levels of 47 patients who fulfilled the ACR criteria of RA. Duration of the disease varied between 3–6 years. CRP and RF levels were also measured from the same sample. Patients were grouped by clinical activity, radiological progression and also by RF and CRP positivity. Our results showed that there was no difference between the serum COMP levels of seropositive and seronegative patients (11.4 vs. 10.71 ng/ml). Serum COMP levels of clinically active patients (11.7 ng/ml) were higher than of patients with inactive disease (10.5 ng/ml) (P < 0.08). The average COMP levels of the radiologically progressive group was higher (12.5 ng/ml) than that of the non-progressive ones (10.3) (P < 0.06). Statistically the highest difference was found between patients with elevated CRP (12.3 ng/ml) and those with normal CRP levels (8.8 ng/ml) (P < 0.03). Significant correlation was also found between serum CRP and COMP levels R:0.54 (P < 0.003). These results confirm previous findings that the serum COMP level reflects the actual degree of cartilage destruction ongoing during the inflammatory process of arthritis, thus can be a useful marker in predicting radiological progression and in monitoring the effectiveness of the treatment of RA.