title: Evaluation of circulating YKL-40 levels in idiopathic interstitial pneumonias.
abstract: BACKGROUND
  YKL-40 is a novel biomarker in diseases with inflammation, fibrosis and tissue remodelling. Previously, circulating YKL-40 was shown to be elevated in patients with idiopathic pulmonary fibrosis (IPF) and was associated with survival.
  
  
  OBJECTIVE
  To compare YKL-40 serum levels between IPF and other interstitial pneumonias such as non-specific interstitial pneumonia (NSIP), smoking-related interstitial lung disease (SR-ILD) and cryptogenic organising pneumonia (COP).
  
  
  METHODS
  Serum YKL-40 levels were measured in 124 healthy controls and 315 patients. Serial measurements were available in 36 patients with IPF and 6 patients with COP.
  
  
  RESULTS
  Serum YKL-40 levels were elevated in all patient groups compared to controls (p < 0.0001), and highest levels were found in the most fibrotic diseases, which showed worst prognosis.
  
  
  CONCLUSIONS
  YKL-40 is highly elevated in fibrotic interstitial pneumonias and may reflect the degree of activity of the fibrogenic process. Remarkably, levels remain high in IPF, but can decrease in other interstitial pneumonias, which appears to be related to a better prognosis.
authors.affiliation: Center of Interstitial Lung Diseases, Department of Pulmonology, St. Antonius Hospital, PO Box 2500, 3430 EM, Nieuwegein, The Netherlands.
authors.forename: Nicoline M
authors.initials: NM
authors.lastname: Korthagen
authors.forename: Coline H M
authors.initials: CH
authors.lastname: van Moorsel
authors.forename: Pieter
authors.initials: P
authors.lastname: Zanen
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Ruven
authors.forename: Jan C
authors.initials: JC
authors.lastname: Grutters
mesh_terms: D054392:Adipokines / Q000097:blood*; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D001992:Bronchoalveolar Lavage Fluid; D016022:Case-Control Studies; D000071451:Chitinase-3-Like Protein 1; D018549:Cryptogenic Organizing Pneumonia / Q000097:blood / Q000175:diagnosis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D054988:Idiopathic Interstitial Pneumonias / Q000097:blood* / Q000175:diagnosis*; D054990:Idiopathic Pulmonary Fibrosis / Q000097:blood / Q000175:diagnosis; D037102:Lectins / Q000097:blood*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D012016:Reference Values; D012189:Retrospective Studies
chemical_list: D054392:Adipokines; D015415:Biomarkers; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D037102:Lectins