title: Airway, but not serum or urinary, levels of YKL-40 reflect inflammation in early cystic fibrosis lung disease.
abstract: BACKGROUND
  Cystic fibrosis (CF) lung disease begins in early life and is progressive with the major risk factor being an exaggerated inflammatory response. Currently, assessment of neutrophilic inflammation in early cystic fibrosis (CF) lung disease relies on bronchoalveolar lavage (BAL). The chitinase-like protein YKL-40 is raised in sputum and serum of adults with CF. We investigated YKL-40 in BAL, serum and urine to determine whether this reflected inflammation and infection in young children with CF.
  
  
  METHODS
  YKL-40 was measured in matched samples of BAL, serum and urine obtained from 36 infants and young children with CF participating in an early surveillance program. Levels were compared to clinical data and markers of inflammation detected in the lung.
  
  
  RESULTS
  YKL-40 in BAL correlated with pulmonary infection [β=1.30 (SE 0.34), p < 0.001] and BAL markers of inflammation [macrophage number: r2 = 0.34, p < 0.001; neutrophil number: r2 = 0.74, p < 0.001; neutrophil elastase: r2 = 0.47, p < 0.001; CXCL8: r2 = 0.45, p < 0.001; IL-β: r2 = 0.62, p < 0.001]. YKL-40 was detectable in serum but levels did not correlate with BAL levels in the same individuals (r2 = 0.04, p = 0.14) or with inflammatory markers. YKL-40 was below the limit of detection in urine (30 pg/ml).
  
  
  CONCLUSIONS
  This study demonstrates that levels of the chitinase-like protein YKL-40 reflect airway inflammation and infection in early CF lung disease. The lack of increased YKL-40 in serum in the absence of systemic inflammation limits the benefit of this potential biomarker in early disease.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Fantino
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Gangell
authors.forename: Dominik
authors.initials: D
authors.lastname: Hartl
authors.affiliation: The Queensland Children's Medical Research Institute, The University of Queensland, Level 4, Foundation Building, Royal Children's Hospital, Herston road, Herston, Brisbane, QLD 4059, Australia. p.sly@uq.edu.au.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Sly
mesh_terms: D054392:Adipokines / Q000032:analysis* / Q000097:blood / Q000652:urine; D015415:Biomarkers / Q000032:analysis; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry*; D002675:Child, Preschool; D000071451:Chitinase-3-Like Protein 1; D003550:Cystic Fibrosis / Q000150:complications / Q000276:immunology*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000209:etiology; D037102:Lectins / Q000032:analysis* / Q000097:blood / Q000652:urine; D008297:Male; D009504:Neutrophils
chemical_list: D054392:Adipokines; D015415:Biomarkers; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D037102:Lectins