title: Serum cartilage oligomeric matrix protein reflects osteoarthritis presence and severity: the Johnston County Osteoarthritis Project.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Duke University, Durham, North Carolina, USA.
authors.forename: A G
authors.initials: AG
authors.lastname: Clark
authors.forename: J M
authors.initials: JM
authors.lastname: Jordan
authors.forename: V
authors.initials: V
authors.lastname: Vilim
authors.forename: J B
authors.initials: JB
authors.lastname: Renner
authors.forename: A D
authors.initials: AD
authors.lastname: Dragomir
authors.forename: G
authors.initials: G
authors.lastname: Luta
authors.forename: V B
authors.initials: VB
authors.lastname: Kraus
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D064236:Cartilage Oligomeric Matrix Protein; D018450:Disease Progression; D016326:Extracellular Matrix Proteins / Q000097:blood*; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006621:Hip Joint / Q000000981:diagnostic imaging; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D064235:Matrilin Proteins; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000097:blood* / Q000000981:diagnostic imaging; D011859:Radiography
chemical_list: D015415:Biomarkers; D064236:Cartilage Oligomeric Matrix Protein; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; C577553:TSP5 protein, human