title: Exhaled breath condensate nitrite--methodological problems of sample collection.
abstract: BACKGROUND
  Exhaled breath condensate (EBC) analysis is a promising new method to monitor airway inflammation, however there are still multiple open methodological questions. The purpose of this study was therefore to investigate methodological influences on nitrite in EBC (surface contamination, flow dependency, storage time and inter- and within day variability).
  
  
  METHODS
  EBC samples of 10 healthy children, 10 healthy adults and 71 asthmatic children were collected and nitrite was analysed using the Griess reaction. Collector devices where either air-dried after disinfection or stored in distilled water till usage. Repeatability measurements were performed at three different times during one day and on five consecutive days. Flow dependency was analysed at 200 and 400 ml/s expiratory flow and storage stability was investigated at several time points within the first three hours after collection of the sample. In a preliminary study EBC nitrite was analysed in asthmatic children of different severity.
  
  
  RESULTS
  Surface contamination appears to have a profound influence on nitrite levels and both within-day and inter-day variability is high. We found no flow dependency, and storage stability was satisfying although with considerable variety in several samples. There were no significant differences between the nitrite levels of the different asthmatic subgroups nor between the asthmatic children and the controls.
  
  
  CONCLUSIONS
  These data indicate that EBC nitrite is a substance with a wide variety of influencing factors and different sources of origin. This has to be kept in mind when using exhaled nitrite as a biomarker for airway inflammation.<br />
authors.affiliation: Department of Pediatrics, University Clinic Carl Gustav Carus, Dresden, Germany. christian.vogelberg@uniklinikum-dresden.de
authors.forename: Christian
authors.initials: C
authors.lastname: Vogelberg
authors.forename: Annegret
authors.initials: A
authors.lastname: Kahlert
authors.forename: Christiane
authors.initials: C
authors.lastname: Würfel
authors.forename: Katarina
authors.initials: K
authors.lastname: Marx
authors.forename: Antje
authors.initials: A
authors.lastname: Böhm
authors.forename: Ursula
authors.initials: U
authors.lastname: Range
authors.forename: Volker
authors.initials: V
authors.lastname: Neumeister
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Leupold
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D002648:Child; D004866:Equipment Contamination; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D007249:Inflammation; D008297:Male; D009573:Nitrites / Q000032:analysis*; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods*
chemical_list: D015415:Biomarkers; D009573:Nitrites