Serum and synovial cartilage oligomeric matrix protein (COMP) in patients with rheumatoid arthritis and osteoarthritis

ObjectiveTo measure serum and synovial COMP levels in rheumatoid arthritis (RA) and osteoarthritis (OA) patients and to assess their correlation with clinical, laboratory and ultrasonographic parameters.MethodsTwo groups of patients were included in this study consisting of 32 patients with RA and 10 patients with knee OA. Ultrasonography of knee joints was performed and serum and synovial Cartilage oligomeric matrix protein (COMP) levels were measured using an inhibition ELISA.ResultsThe mean synovial COMP level was significantly higher in RA compared to OA patients (14.3 ± 5.19μg/mL and 9.26 ±2.42 μg/mL respectively, P< 0.01). Amongst RA patients, it was higher in those with erosions. COMP levels were higher in synovial fluid compared to serum levels in both groups (P <0.01). Amongst RA patients, synovial COMP levels showed a significant positive correlation with synovial membrane thickness on ultrasonography (P <0.001), and significant negative correlation with the cartilage thickness (P <0.001). In OA group, synovial and serum COMP level showed significant positive correlation with WOMAC index for the lower limbs (r= 0.64, P < 0.05, and r=0.92, P <0.001 respectively) and a significant negative correlation with cartilage thickness (P <0.001).ConclusionThe synovial COMP and ultrasonographic joint evaluation may be considered as markers of disease activity and cartilage destruction in both RA and OA patients.