title: Circulating surfactant protein D as a potential lung-specific biomarker of health outcomes in COPD: a pilot study.
abstract: BACKGROUND
  There is a paucity of surrogate lung-specific biological markers that can be used to track disease progression and predict clinical outcomes in chronic obstructive pulmonary disease (COPD). The principal aim of this pilot study was to determine whether circulating surfactant protein D (SPD) or Clara Cell protein-16 (CC16) levels are associated with lung function or health status in patients with severe COPD.
  
  
  METHODS
  We studied 23 patients with advanced COPD. Lung function measurements, Chronic Respiratory Disease Questionnaire (CRQ) scores, and serum levels of SPD, CC16, and C-reactive protein (CRP) were determined at baseline and at 3 months.
  
  
  RESULTS
  At baseline, FEV(1) was inversely associated with serum SPD levels (P = 0.045) but not with CC16 (P = 0.675) or CRP levels (P = 0.549). Over a 3 month period, changes in SPD levels correlated significantly with changes in CRQ scores (adjusted P = 0.008) such that patients who had the largest declines in serum SPD levels experienced the largest gains in health status. The association was particularly notable between circulating SPD level and the dyspnea domain of the CRQ score (P = 0.018). Changes in CC16 or CRP levels did not correlate with changes in CRQ scores.
  
  
  CONCLUSIONS
  Changes in serum SPD levels tracked well with changes in health status over a 3 month period in patients with severe COPD. These data suggest that circulating SPD levels may be useful biomarkers to track health outcomes of COPD patients.
authors.affiliation: The University of British Columbia (Respiratory Division), Vancouver, BC. dsin@mrl.ubc.ca
authors.forename: Don D
authors.initials: DD
authors.lastname: Sin
authors.forename: Rochelle
authors.initials: R
authors.lastname: Leung
authors.forename: Wen Q
authors.initials: WQ
authors.lastname: Gan
authors.forename: Sf Paul
authors.initials: SP
authors.lastname: Man
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism; D018450:Disease Progression; D005260:Female; D005541:Forced Expiratory Volume; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000503:physiopathology*; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood*; D014598:Uteroglobin / Q000097:blood; D014797:Vital Capacity
chemical_list: D015415:Biomarkers; D037663:Pulmonary Surfactant-Associated Protein D; C556389:SCGB1A1 protein, human; D002097:C-Reactive Protein; D014598:Uteroglobin