title: Analysis of nitrogen oxides (NOx) in the exhaled breath condensate (EBC) of subjects with asthma as a complement to exhaled nitric oxide (FeNO) measurements: a cross-sectional study.
abstract: BACKGROUND
  The study of pulmonary biomarkers with noninvasive methods, such as the analysis of exhaled breath condensate (EBC), provides a useful approach to the pathophysiology of asthma. Although many recent publications have applied such methods, numerous methodological pitfalls remain. The first stage of our study consisted of validating methods for the collection, storage and analysis of EBC; we next sought to clarify the utility of analysing nitrogen oxides (NOx) in the EBC of asthmatics, as a complement to measuring exhaled nitric oxide (FeNO).
  
  
  METHODS
  This hospital-based cross-sectional study included 23 controls matched with 23 asthmatics. EBC and FeNO were performed and respiratory function measured. Intra-assay and intra-subject reproducibility were assessed for the analysis of NOx in the EBC of 10 healthy subjects.
  
  
  RESULTS
  The intraclass correlation coefficient (ICC) was excellent for intra-assay reproducibility and was moderate for intra-subject reproducibility (Fermanian's classification). NOx was significantly higher in asthmatics (geometric mean [IQR] 14.4 μM [10.4 - 19.7] vs controls 9.9 μM [7.5 - 15.0]), as was FeNO (29.9 ppb [17.9 - 52.4] vs controls 9.6 ppb [8.4 - 14.2]). FeNO also increased significantly with asthma severity.
  
  
  CONCLUSIONS
  We validated the procedures for NOx analysis in EBC and confirmed the need for assays of other biomarkers to further our knowledge of the pathophysiologic processes of asthma and improve its treatment and control.
authors.affiliation: Univ Lille Nord de France, F-59 000 Lille, France. nathalie.cherot@univ-lille2.fr.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Chérot-Kornobis
authors.forename: Sébastien
authors.initials: S
authors.lastname: Hulo
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Edmé
authors.forename: Virginie
authors.initials: V
authors.lastname: de Broucker
authors.forename: Régis
authors.initials: R
authors.lastname: Matran
authors.forename: Annie
authors.initials: A
authors.lastname: Sobaszek