title: Differences in exhaled breath condensate pH measurements between samples obtained with two commercial devices.
abstract: BACKGROUND
  The objective of this study was to determine differences in EBC pH between samples obtained by RTube and EcoScreen, and to identify the effect of storage at -80 degrees C on the pH values.
  
  
  METHODS
  Twenty-three nonsmoking subjects with asthma or allergic rhinitis or without respiratory disease performed two sequential exhaled breath condensate (EBC) collections, using the RTube collection system and the EcoScreen condenser. EBC pH was measured immediately after collection and after storage at -80 degrees C for 8 weeks, without deaeration and repeated following deaeration with Argon.
  
  
  RESULTS
  In EBC samples without deaeration, the EcoScreen pH values were significantly higher than the RTube pH values (mean difference, 0.32; 95% CI, 0.21-0.44, P < 0.0001). In deaerated EBC samples, the EcoScreen pH values were also significantly higher than the RTube pH values (mean difference, 0.12; 95% CI, 0.01-0.25, P=0.04). For both EBC collection systems, storage for 8 weeks had a significant influence on pH of nondeaerated samples.
  
  
  CONCLUSIONS
  The present study demonstrates that EBC pH value is dependent on the collection device used and that the storage for 8 weeks had a significant influence on the pH of samples analyzed without deaeration.
authors.affiliation: Seccion de Alergologia, Hospital Universitario Dr. Peset, C/Gaspar Aguilar 90, 46017 Valencia, Spain. prieto_jes@gva.es
authors.forename: L
authors.initials: L
authors.lastname: Prieto
authors.forename: A
authors.initials: A
authors.lastname: Ferrer
authors.forename: J
authors.initials: J
authors.lastname: Palop
authors.forename: J
authors.initials: J
authors.lastname: Domenech
authors.forename: R
authors.initials: R
authors.lastname: Llusar
authors.forename: R
authors.initials: R
authors.lastname: Rojas
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis*; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D016022:Case-Control Studies; D045853:Exhalation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008875:Middle Aged; D012220:Rhinitis / Q000175:diagnosis*; D013696:Temperature; D013997:Time Factors
chemical_list: D015415:Biomarkers