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Objective: Previous descriptions of potential biomarkers of osteoarthritis (OA) have been limited to Caucasians. In the present study, we examined associations between serum levels of cartilage oligomeric matrix protein (COMP) and ethnicity (African American or Caucasian) and sex in the Johnston County Osteoarthritis Project, a population-based study of OA in rural North Carolina., Methods: All African Americans and a randomly selected sample of Caucasians who had available sera and either no radiographic evidence of knee or hip OA according to the Kellgren/Lawrence (K/L) system (K/L grade 0) or radiographic evidence of knee OA (K/L grade 2 or higher) were included. Serum COMP levels were quantified by sandwich enzyme-linked immunosorbent assay, using monoclonal antibodies 16-F12 and 17-C10. Linear regression models were used to assess relationships between serum levels of natural log-transformed COMP (ln COMP) and ethnicity and sex, controlling for age, height, body mass index (BMI), radiographic OA, and the presence of other symptomatic joints. Radiographic OA was defined in separate models as the presence, severity, and laterality of radiographic knee OA, the co-occurrence of radiographic knee and hip OA, and the number of knees and hips with radiographic OA., Results: The 769 subjects in the study sample had a mean +/- SD age of 62 +/- 10.3 years. Levels of ln COMP were associated with age, BMI, and all definitions of radiographic OA (P = 0.0001), and varied by ethnicity and sex. In adjusted models, ln COMP was higher in African American women than in Caucasian women (P = 0.003) and higher in Caucasian men than Caucasian women (P = 0.0001). There were no statistically significant differences in serum ln COMP levels between African American men and women., Conclusion: Serum COMP levels vary by ethnicity and sex. These factors should be considered in the derivation of standards using this, and possibly other, potential biomarkers of OA.

Objective: To examine the cross-sectional relationship between serum cartilage oligomeric matrix protein (COMP) and hip and knee clinical signs and symptoms in a sample of adults without radiographic hip or knee osteoarthritis (OA)., Design: A total of 145 persons with available sera and no evidence of radiographic hip or knee OA (Kellgren-Lawrence grade 0) were randomly selected from the Caucasian participants of the Johnston County Osteoarthritis Project. COMP was quantified by a competitive ELISA assay with a monoclonal antibody 17-C10. Hip and knee clinical signs and symptoms were assessed by physical examination and interview, and their associations with Ln COMP analysed with general linear models., Results: After adjustment for age, gender, body mass index (BMI), and other symptomatic joints, mean Ln COMP was statistically significantly higher among persons with hip-related clinical signs (P=0.018), among those with hip-related symptoms (P=0.046), and among individuals meeting American College of Rheumatology clinical criteria for hip OA (P=0.021). There were no statistically significant associations between any of the knee-related clinical signs and symptoms and Ln COMP., Conclusion: Serum COMP may be useful as a biomarker of pre-radiographic hip joint pathology; its utility as a biomarker of pre-radiographic knee joint pathology is unclear., (Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved.)

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 baseline evaluation as part of the Johnston County Osteoarthritis Project, a population-based study of OA in rural North Carolina. A total of 291 Caucasian participants were randomly selected for COMP analysis, 143 patients with radiographic knee OA (Kellgren/Lawrence [K/L] grade > or = 2) and 148 controls with neither hip nor knee OA (K/L grade 0), evenly distributed by age and gender. COMP was quantified by competitive enzyme-linked immunosorbent assay with monoclonal antibody 17-C10. The natural log-transformed COMP data were analyzed using general linear models., Results: Serum COMP levels were significantly elevated (P = 0.0001) in the age > or = 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 significantly higher than those of the control group (1,208.57 +/- 487.47 ng/ml versus 1,061.83 +/- 370.58 ng/ml; P = 0.0093). Serum COMP levels also increased significantly 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 no significant difference in serum COMP levels by gender or obesity., Conclusion: We demonstrate that in a population-based sample, serum COMP levels can distinguish an OA-affected subgroup from an unaffected subgroup and can reflect disease severity and multiple joint involvement in OA.