title: Reproducibility of biomarkers in induced sputum and in serum from chronic smokers.
abstract: BACKGROUND
  Soluble inflammatory markers obtained from non-invasive airway sampling such as induced sputum may be useful biomarkers for targeted pharmaceutical interventions. However, before these soluble markers can be used as potential targets, their variability and reproducibility need to be established in distinct study populations.
  
  
  OBJECTIVE
  This study aimed to assess the reproducibility of biomarkers obtained from induced sputum and serum in chronic smokers and non-smokers.
  
  
  METHODS
  Sputum and serum samples were obtained from 16 healthy non-smokers and 16 asymptomatic chronic smokers (for both groups: 8M/8F, 30-52 years, FEV1 ≥80% pred.; ≥10 pack years for the smokers) on 2 separate visits 4-10 days apart. Soluble markers in serum and sputum were analysed by ELISA. The differences between smokers vs non-smokers were analysed with a t-test and variability was assessed on log-transformed data by a mixed model ANOVA.
  
  
  RESULTS
  Analysable sputum samples could be obtained from all 32 subjects. In both study populations neutrophils and macrophages were the predominant cell types. Serum Pulmonary Surfactant Associated Protein D had favourable reproducibility criteria for reliability ratio (0.99), intra-subject coefficient of variation (11.2%) and the Bland Altman limits of agreement. Furthermore, chronic smokers, compared to non-smokers, had significantly higher sputum concentrations of IL-8 (1094.6 pg/mL vs 460.8 pg/mL, p = 0.006)), and higher serum concentrations of Pulmonary Surfactant Associated Protein D (110.9 pg/mL vs 64.7 pg/mL, p = 0.019), and lower concentrations of Serum Amyloid A (1352.4 pg/mL vs 2297.5 pg/mL, p = 0.022).
  
  
  CONCLUSIONS
  Serum Pulmonary Surfactant Associated Protein D proved to be a biomarker that fulfilled the criteria for reproducibility in both study groups.
authors.affiliation: Centre for Human Drug Research, Leiden, The Netherlands. Electronic address: RZuiker@CHDR.nl.
authors.forename: Rob G J A
authors.initials: RG
authors.lastname: Zuiker
authors.affiliation: Centre for Human Drug Research, Leiden, The Netherlands.
authors.forename: Ingrid M C
authors.initials: IM
authors.lastname: Kamerling
authors.affiliation: VU Medical Center, Amsterdam, The Netherlands.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Morelli
authors.affiliation: Janssen Research & Development, LLC, Spring House, Pennsylvania, USA.
authors.forename: Cesar
authors.initials: C
authors.lastname: Calderon
authors.affiliation: HAL Allergy B.V., Leiden, The Netherlands.
authors.forename: J Diderik
authors.initials: JD
authors.lastname: Boot
authors.affiliation: Centre for Human Drug Research, Leiden, The Netherlands.
authors.forename: Marieke
authors.initials: M
authors.lastname: de Kam
authors.affiliation: Institute for Clinical Science, Skane University Hospital, Dept of Respiratory Medicine and Allergology, Lund, Sweden; University of Groningen, Univ Med Ctr Groningen, Dept of Clinical Pharmacy & Pharmacology, Groningen, The Netherlands; University of Groningen, Univ Med Ctr Groningen, Dept of Gen Practice, Groningen, The Netherlands.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Diamant
authors.affiliation: Centre for Human Drug Research, Leiden, The Netherlands.
authors.forename: Jacobus
authors.initials: J
authors.lastname: Burggraaf
authors.affiliation: Centre for Human Drug Research, Leiden, The Netherlands.
authors.forename: Adam F
authors.initials: AF
authors.lastname: Cohen
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000378:metabolism; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood*; D015203:Reproducibility of Results; D000685:Serum Amyloid A Protein / Q000378:metabolism*; D012907:Smoking / Q000378:metabolism*; D013183:Sputum / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D016209:Interleukin-8; D037663:Pulmonary Surfactant-Associated Protein D; D000685:Serum Amyloid A Protein
keywords: Biomarkers; Chronic smokers; Pulmonary surfactant associated protein D; Serum; Sputum