Serum levels of KL-6 as a useful marker for evaluating pulmonary fibrosis in patients with systemic sclerosis

J Rheumatol. 2000 Apr;27(4):930-4.


Objective: KL-6 is a mucin-like glycoprotein that is strongly expressed on type II pneumocytes in the lung. Circulating KL-6 has been shown to be a sensitive marker of the disease activity of interstitial lung diseases. We determined the serum levels of KL-6 in patients with systemic sclerosis (SSc) and investigated whether these levels would serve as a useful marker of pulmonary fibrosis (PF) in patients with SSc.

Methods: The serum KL-6 levels were determined using a specific ELISA in 91 patients with SSc, and in 38 healthy controls.

Results: The serum levels of KL-6 were significantly higher in patients with SSc than in healthy controls (923+/-860 vs. 382+/-55 U/ml; p<0.0001). The serum KL-6 levels of the patients with diffuse cutaneous SSc (dSSc) tended to be higher than those with limited cutaneous SSc (ISSc) (1054+/-1000 vs. 800+/-694 U/ml), but there was no significant difference between these 2 groups. The serum KL-6 levels in the patients with PF were significantly elevated compared to those without PF (1283+/-1056 vs. 520+/-148 U/ml; p<0.0001). Moreover, DLCO and VC were also significantly decreased in the patients with elevated KL-6 levels compared to those with normal levels (62+/-22% vs. 72+/-17%, p<0.05; 87 +/-20% vs. 100+/-18%, p<0.01, respectively).

Conclusion: Serum KL-6 level may be a useful serum marker for evaluating pulmonary fibrosis in patients with SSc.

MeSH terms

  • Adult
  • Antigens / blood*
  • Antigens, Neoplasm
  • Autoantibodies / blood
  • Biomarkers
  • DNA Topoisomerases, Type I / immunology
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Glycoproteins / blood*
  • Humans
  • Lung / enzymology
  • Lung / immunology
  • Lung / pathology
  • Male
  • Middle Aged
  • Mucin-1
  • Mucins
  • Predictive Value of Tests
  • Pulmonary Fibrosis* / blood
  • Pulmonary Fibrosis* / diagnosis
  • Pulmonary Fibrosis* / etiology
  • Scleroderma, Systemic / complications*


  • Antigens
  • Antigens, Neoplasm
  • Autoantibodies
  • Biomarkers
  • Glycoproteins
  • MUC1 protein, human
  • Mucin-1
  • Mucins
  • DNA Topoisomerases, Type I