title: Exhaled breath condensate pH does not discriminate asymptomatic gastroesophageal reflux or the response to lansoprazole treatment in children with poorly controlled asthma.
abstract: BACKGROUND
  Although exhaled breath condensate (EBC) pH has been identified as an "emerging" biomarker of interest for asthma clinical trials, the clinical determinants of EBC pH remain poorly understood. Other studies have associated acid reflux-induced respiratory symptoms, for example, cough, with transient acidification of EBC.
  
  
  OBJECTIVE
  We sought to determine the clinical and physiologic correlates of EBC acidification in a highly characterized sample of children with poorly controlled asthma. We hypothesized that (1) children with asymptomatic gastroesophageal reflux determined by 24-hour esophageal pH monitoring would have a lower EBC pH than children without gastroesophageal reflux, (2) treatment with lansoprazole would alter EBC pH in those children, and (3) EBC acidification would be associated with increased asthma symptoms, poorer asthma control and quality of life, and increased formation of breath nitrogen oxides (NOx).
  
  
  METHODS
  A total of 110 children, age range 6 to 17 years, with poor asthma control and esophageal pH data enrolled in the Study of Acid Reflux in Children with Asthma (NCT00442013) were included. Children submitted EBC samples for pH and NOx measurement at randomization and at study weeks 8, 16, and 24.
  
  
  RESULTS
  Serial EBC pH measurements failed to distinguish asymptomatic gastroesophageal reflux and was not associated with breath NOx formation. EBC pH also did not discriminate asthma characteristics such as medication and health care utilization, pulmonary function, and asthma control and quality of life both at baseline and across the study period.
  
  
  CONCLUSIONS
  Despite the relative ease of EBC collection, EBC pH as a biomarker does not provide useful information of children with asthma who were enrolled in asthma clinical trials.
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Ga; Center for Developmental Lung Biology, Children's Healthcare of Atlanta, Atlanta, Ga. Electronic address: anne.fitzpatrick@emory.edu.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Fitzpatrick
authors.affiliation: Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, Md.
authors.forename: Janet T
authors.initials: JT
authors.lastname: Holbrook
authors.affiliation: Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, Md.
authors.forename: Christine Y
authors.initials: CY
authors.lastname: Wei
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Ga.
authors.forename: Meredith S
authors.initials: MS
authors.lastname: Brown
authors.affiliation: Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Md.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wise
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Va.
authors.forename: W Gerald
authors.initials: WG
authors.lastname: Teague
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D002648:Child; D004311:Double-Blind Method; D005260:Female; D005764:Gastroesophageal Reflux / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D064747:Lansoprazole / Q000627:therapeutic use*; D008168:Lung / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D009589:Nitrogen Oxides / Q000378:metabolism; D054328:Proton Pump Inhibitors / Q000627:therapeutic use*; D012129:Respiratory Function Tests
chemical_list: D015415:Biomarkers; D009589:Nitrogen Oxides; D054328:Proton Pump Inhibitors; D064747:Lansoprazole
keywords: Airway acidification; Airway inflammation; Asthma; Asthma biomarker; Asthma clinical trial; Children; Exhaled breath condensate; Gastroesophageal reflux