Serum YKL-40 concentrations in patients with rheumatoid arthritis: relation to disease activity

Rheumatology (Oxford). 1999 Jul;38(7):618-26. doi: 10.1093/rheumatology/38.7.618.


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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipokines
  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Inflammatory Agents / therapeutic use
  • Antirheumatic Agents / therapeutic use
  • Arthritis, Rheumatoid / blood*
  • Arthritis, Rheumatoid / drug therapy
  • Biomarkers / blood
  • Chitinase-3-Like Protein 1
  • Disease Progression
  • Female
  • Glycoproteins / blood*
  • Humans
  • Lectins
  • Male
  • Methotrexate / therapeutic use
  • Middle Aged
  • Prednisolone / therapeutic use
  • Severity of Illness Index


  • Adipokines
  • Anti-Inflammatory Agents
  • Antirheumatic Agents
  • Biomarkers
  • CHI3L1 protein, human
  • Chitinase-3-Like Protein 1
  • Glycoproteins
  • Lectins
  • Prednisolone
  • Methotrexate