Serum cartilage oligomeric matrix protein reflects osteoarthritis presenceand severity - The Johnston county osteoarthritis project

Objective. To characterize serum cartilage oligomeric matrix protein (COMP) levels by age and gender for a radiographically defined population free of hip and knee osteoarthritis (OA), and to examine the potential utility of COMP as a diagnostic biomarker for knee OA. Methods. Serum samples and knee and hip radiographs were obtained at a base line evaluation as part of the Johnston County Osteoarthritis Project, a po pulation-based study of OA in rural North Carolina. A total of 291 Caucasia n participants were randomly selected for COMP analysis, 143 patients with radiographic knee OA (Kellgren/Lawrence [K/L] grade greater than or equal t o 2) and 148 controls with neither hip nor knee OA (KIL grade 0), evenly di stributed by age and gender. COMP was quantified by competitive enzyme-link ed immunosorbent assay with monoclonal antibody 17-C10, The natural log-tra nsformed COMP data were analyzed using general linear models. Results, Serum COMP levels were significantly elevated (P = 0.0001) in the age greater than or equal to 65 group (mean +/- SD 1,302.1 +/- 496.7 ng/ml) versus the age 45-54 and age 55-64 groups (1,058.1 +/- 432.4 and 1,038.6 /- 313,3, respectively), Serum COMP levels of the OA group were significant ly higher than those of the control group (1,208.57 +/- 487.37 ng/ml versus 1,061.83 +/- 370.58 ng/ml; P = 0.0093, Serum COMP levels also increased si gnificantly with knee OA K/L grade (P = 0.0047), knee OA laterality (P = 0. 0043), and number of knee and hip joints involved (P = 0.0001), There was n o significant difference in serum COMP levels by gender or obesity. Conclusion. We demonstrate that in a population-based sample, serum COMP le , els can distinguish an OA-affected subgroup from an unaffected subgroup a nd can reflect disease severity and multiple joint involvement in OA.