title: Levels of surfactant proteins A and D and KL-6 are elevated in the induced sputum of chronic obstructive pulmonary disease patients: a sequential sputum analysis.
abstract: BACKGROUND
  Recent clinical studies have suggested that serum surfactant protein (SP) A, SP-D and Krebs von den Lungen-6 (KL-6) are potential biomarkers for interstitial lung diseases. Serum levels of SP-A and SP-D have also been found to be elevated in chronic obstructive pulmonary disease (COPD), but their significance has not been evaluated or compared in induced sputum samples obtained directly from the airways.
  
  
  OBJECTIVE
  A sequential sputum analysis was conducted to assess the value of SP-A, SP-D and KL-6 levels in COPD.
  
  
  METHODS
  The study material consisted of induced sputum samples from 61 subjects, 28 with COPD and 33 with prolonged cough (cough lasting >3 weeks and normal spirometry). Sputum was collected in 3 fractions (3 periods of 5 min each). Sputum levels of these proteins were measured, and receiver operating characteristic curve analysis was carried out to evaluate the sensitivity, specificity and area under the curve (AUC) for each fraction.
  
  
  RESULTS
  The levels of SP-A, SP-D and KL-6 were higher in patients with COPD than in those with prolonged cough in each of the fractions. Sputum levels of these proteins correlated inversely with obstruction and positively with ageing, smoking history, sputum macrophages and eosinophils. Sputum fractionation had a relatively minor effect on the levels and AUC of these proteins.
  
  
  CONCLUSIONS
  Sequential sputum analysis from 3 consecutive fractions indicated a significant difference in the levels of SP-A, SP-D and KL-6 between COPD and prolonged cough. However, sputum fractionation itself had a relatively minor effect on the levels of these proteins.
authors.affiliation: Department of Molecular and Internal Medicine, Graduate School of Biomedical Science, Hiroshima University, Hiroshima, Japan.
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Ishikawa
authors.forename: Noboru
authors.initials: N
authors.lastname: Hattori
authors.forename: Sonosuke
authors.initials: S
authors.lastname: Tanaka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Horimasu
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Haruta
authors.forename: Akihito
authors.initials: A
authors.lastname: Yokoyama
authors.forename: Nobuoki
authors.initials: N
authors.lastname: Kohno
authors.forename: Vuokko L
authors.initials: VL
authors.lastname: Kinnula
mesh_terms: D000368:Aged; D000375:Aging; D019540:Area Under Curve; D003371:Cough / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018396:Mucin-1 / Q000032:analysis*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000378:metabolism*; D037662:Pulmonary Surfactant-Associated Protein A / Q000032:analysis*; D037663:Pulmonary Surfactant-Associated Protein D / Q000032:analysis*; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012907:Smoking; D013183:Sputum / Q000737:chemistry*
chemical_list: C060192:MUC1 protein, human; D018396:Mucin-1; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D