AB0275 The correlation of cartilage oligomeric matrix protein with sonographic knee cartilage thickness and disease characteristics in rheumatoid arthritis

Background Cartilage Oligomeric Matrix Protein (COMP) is an extracellular protein which is primarily found in the cartilage and to a lesser extent in ligaments, meniscus, tendons and synovium. Experimental models of rheumatoid arthritis (RA) and osteoarthritis have pointed out that serum COMP levels are reflective of the cartilage turnover rate. Objectives To investigate the correlation of serum COMP levels with the articular cartilage damage based on sonographic knee cartilage thickness (KCT) and disease characteristics in RA. Methods A total of 61 RA patients and 27 healthy controls were recruited in this study. Serum samples were obtained from all subjects to determine the COMP levels. All subjects had bilateral ultrasound scan of their knees performed by a single radiologist; who was blinded to the details of the subjects. The KCT was based on the mean of measurements at 3 sites; the medial condyle, lateral condyle and intercondylar notch (Figure 1). Besides, the RA patients were assessed for their disease activity based on DAS 28. Results Serum COMP concentrations were significantly elevated in the RA patients compared to the controls (p=0.001). The serum COMP levels had an inverse relationship with bilateral KCT in RA subjects and the healthy controls. However, the association was statistically insignificant for bilateral knees in the control arm. COMP correlated significantly with disease activity based on DAS 28 (r =0.299, p=0.010), disease duration (r =0.439,p = Conclusions The serum COMP is a promising biomarker in RA which reflects disease activity and damage to the articular cartilage. Serum COMP appeared superior to the traditional markers in RA i.e ESR and CRP in predicting sonographic KCT. References Andersson ML, Svensson B, Petersson IF, et al. Early increase in serum-COMP is associated with joint damage progression over the first five years in patients with rheumatoid arthritis. BMC Musculoskelet Disord. 2013;14:229. Happonen KE, Saxne T, Aspberg A, et al. Regulation of complement by cartilage oligomeric matrix protein allows for a novel molecular diagnostic principle in rheumatoid arthritis. Arthritis Rheum. 2010;62:3574–83. Happonen KE, Saxne T, Geborek P, et al. Serum COMP-C3b complexes in rheumatic diseases and relation to anti-TNF-alpha treatment. Arthritis Res Ther. 2012;14:R15. Disclosure of Interest None declared