Knee osteoarthritis (OA) is a major cause of joint dysfunction, pain and disability.

1. LONGITUDINAL STUDY OF SERUM CARTILAGE OLIGOMERIC MARTIX PROTEIN (COMP) AND PHASIC PROGRESSION OF KNEE OSTEOARTHRITIS M Sharif 1, JR Kirwan2, RGranell2,3, S Clarke2 1Dept of Anatomy, 2Rheumatology Unit, 3Dept of Mathematics and 4Dept of Pathology & Microbiology University of Bristol, UK Federation of European Connective Tissue Societies, Taormina-Giardini Naxos, Sicily, 9-13th July 2004. RESULTS BACKGROUND • Knee osteoarthritis (OA) is a major cause of joint dysfunction, pain and disability. • In 1996 we recruited a cohort of patients with predominantly medial tibiofemoral OA of the knee to monitor the natural progression of the disease sequentially over 5 years and to test the hypothesis that progression of OA is episodic or phasic. • We report here the analysis of longitudinal measurements of serum cartilage oligomeric matrix protein (COMP) in relation to disease outcome at the end of the study. • Complete data was available on 115/135 patients of which 37 progressed (22 by TKR and 15 by ∆TFJ≥2mm). The mean (SD) ages of the progressors and non-progressors were 64.2 (7.8) years and 63.3 (10.6) year, and proportion of females 51% and 56% respectively. • Baseline [COMP] was significantly higher in the progressors compared to the non-progressors (Figure 1). • The probability of progression increases with increasing serum concentrations of COMP (Figure 2). • 7/37 patients progressed between 0–2 years and again 3-5 years by the same criteria. In these patients serum COMP was higher during both periods of progression . METHODS • Patients with knee pain and radiographic evidence of OA had clinical examination and blood samples at 0, 6, 12, 18, 24, 30, 36, 42, 48 and 60 months. • Plain knee x-rays were taken at 0, 2, 3 and 5 years and read ‘blind’ using standard techniques • OA progression was defined by previously used criteria (reduction of joint space by at least 2mm in the tibiofemoral joint space [∆TFJ≥2 mm] or total knee replacement [TKR]). • Serum COMP was measured using a COMP ELISA kit (AnaMar Medical, Lund, Sweden). • Ordered logistic regression modeling was performed to determine the probability of progression in relation to serum COMP concentrations [COMP]. CONCLUSIONS • Elevated COMP concentrations are associated with progression of knee OA. • Ordered logistic regression analysis has shown that for each unit rise in serum COMP the probability of progression increases by 15%. • The patterns of progression seen in some of the patients are consistent with the hypothesis that progression of knee OA is episodic or phasic. Figure 1: Serum COMP concentrations at entry to the study in relation to disease outcome at 5 year follow up. The horizontal bars indicate the mean in each group. Acknowledgements: This study was supported by the Arthritis and Rheumatism Council, UK;Hoffmann-La Roche Ltd, Roche Diagnostics, Switzerland; and the NHS Executive South West Research and Development Directorate, Bristol, UK. We are grateful to AnaMar Medical for measuring the serum COMP concentrations.