title: Serum YKL-40 concentrations in patients with rheumatoid arthritis: relation to disease activity.
abstract: OBJECTIVE
  YKL-40, also called human cartilage glycoprotein-39, is secreted by chondrocytes, synovial cells, macrophages and neutrophils. Studies have shown that YKL-40 is an autoantigen in rheumatoid arthritis (RA). We evaluated whether serum YKL-40 was related to disease activity in patients with RA.
  
  
  METHODS
  Serum YKL-40 was determined by radioimmunoassay in 156 patients with RA during a 1 yr longitudinal study.
  
  
  RESULTS
  Serum YKL-40 was increased in 54% of the patients with clinically active disease. Patients with clinically active disease initially who became inactive after 12 months had a significant decrease in serum YKL-40 (-30%, P < 0.002) and patients who changed from inactive to active disease had an increase in serum YKL-40. Patients who remained active had unchanged serum YKL-40 during the study. Serum YKL-40 decreased rapidly (-24% after 7 days, P < 0.01) during prednisolone therapy, and more slowly in patients treated with methotrexate only (-15% after 60 days, P < 0.01). Patients with early RA (disease duration < 3 yr, n = 50) and a persistently elevated serum YKL-40 were at risk of radiological disease progression as determined by Larsen score.
  
  
  CONCLUSIONS
  Serum YKL-40 varies according to disease activity in RA, but provides in some respect information different from conventional markers. Our previous studies are consistent with a local release of YKL-40 in the arthritic joint followed by a secondary increase in serum YKL-40. YKL-40 may prove to be a new tool for the study of disease activity and pathophysiology of RA.
authors.affiliation: Department of Rheumatology, Hvidovre Hospital, Denmark.
authors.forename: J S
authors.initials: JS
authors.lastname: Johansen
authors.forename: M
authors.initials: M
authors.lastname: Stoltenberg
authors.forename: M
authors.initials: M
authors.lastname: Hansen
authors.forename: A
authors.initials: A
authors.lastname: Florescu
authors.forename: K
authors.initials: K
authors.lastname: Hørslev-Petersen
authors.forename: I
authors.initials: I
authors.lastname: Lorenzen
authors.forename: P A
authors.initials: PA
authors.lastname: Price
mesh_terms: D054392:Adipokines; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy; D015415:Biomarkers / Q000097:blood; D000071451:Chitinase-3-Like Protein 1; D018450:Disease Progression; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D037102:Lectins; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use; D008875:Middle Aged; D011239:Prednisolone / Q000627:therapeutic use; D012720:Severity of Illness Index
chemical_list: D054392:Adipokines; D000893:Anti-Inflammatory Agents; D018501:Antirheumatic Agents; D015415:Biomarkers; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins; D037102:Lectins; D011239:Prednisolone; D008727:Methotrexate