Role of cartilage oligomeric matrix protein (COMP) as a prognostic biomarker in follow-up of early rheumatoid arthritis patients: Correlation to musculoskeletal ultrasonographic findings

To assess the level of serum cartilage oligomeric matrix protein (COMP) in early rheumatoid arthritis (RA) patients and study its relation to disease activity and musculoskeletal ultrasound (MSUS) findings. The study included 40 early RA patients. Disease activity score (DAS28) was assessed. Serum COMP level was measured and MSUS findings of the small joints of hands done at base line and after 6 months of follow up.20 age and sex matched control were included. Patients age was 38.8 ± 9.3 years; 36 females and 4 males and disease duration 6.7 ± 3.5 years. Serum COMP was significantly higher in patients (median 190 U/L; 90–750 U/L) compared to control (90 U/L; 80–130 U/L)(p < .001) being higher in more active (250 U/L) (p = .001) and significantly correlated with baseline synovial inflammation (p = .009). COMP levels were lowered after 6 months of receiving treatment (110 U/L; 30–180 U/L) (p < .001). The presence of bony erosions increased with more active disease (p = .003). There was a significant reduction in the erythrocyte sedimentation rate and COMP at follow up (p < .0001 and p = .001 respectively). No correlation was found between the COMP level with C-reactive protein, ESR, MSUS score or bony erosions at follow up. COMP significantly correlated with disease activity in early RA and could be used as a marker of activity. It correlates significantly with synovial inflammation detected by power Doppler. COMP may reflect the outcome and could be used as a prognostic marker in RA patients. COMP did not significantly correlate with bone erosions.