title: Integrating lung and plasma expression of pneumo-proteins in developing biomarkers in COPD: a case study of surfactant protein D.
abstract: BACKGROUND
  Surfactant protein D (SP-D) is a promising blood biomarker in patients with chronic obstructive pulmonary disease (COPD). Nevertheless, circulating levels of SP-D are not related to pulmonary functions. In the present exploratory study, we created a simple index of plasma to bronchoalveolar lavage (BAL) fluid ratio of SP-D (pSP-D/bSP-D), and determined whether this index would relate to the severity of airflow limitation and hence represent a superior biomarker than pSP-D alone.
  
  
  METHODS
  In 50 ex and current smokers (mean age 57.6±7.8 years, 74% men), SP-D was measured in BAL fluid and plasma samples, and the relationships between spirometric variables and a composite parameter - the pSP-D/bSP-D ratio were determined.
  
  
  RESULTS
  There was a significant inverse correlation between the pSP-D/bSP-D ratio and the severity of airflow obstruction, as measured by FEV1/FVC (p=0.012). In contrast, no relationship was observed between FEV1/FVC and pSP-D alone.
  
  
  CONCLUSIONS
  We suggest that integrating both lung and plasma expression of pneumo-proteins may be more useful than plasma expression alone in developing pneumo-proteins as potential biomarkers in COPD.
authors.affiliation: Department of Respiratory Medicine and Tuberculosis, Faculty of Medicine, P.J. Safarik University and L. Pasteur Teaching Hospital, Kosice, Slovakia. ruzena.tkacova@upjs.sk
authors.forename: Ruzena
authors.initials: R
authors.lastname: Tkacova
authors.forename: Annette
authors.initials: A
authors.lastname: McWilliams
authors.forename: Stephen
authors.initials: S
authors.lastname: Lam
authors.forename: Don D
authors.initials: DD
authors.lastname: Sin
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000473:pathology; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood*; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D012907:Smoking / Q000503:physiopathology
chemical_list: D015415:Biomarkers; D037663:Pulmonary Surfactant-Associated Protein D