title: Nasal potential difference: Best or average result for CFTR function as diagnostic criteria for cystic fibrosis?
abstract: BACKGROUND
  The current practice of averaging the nasal potential difference (NPD) results of right and left nostril measurements reduce inter-individual variability but may underestimate individual CFTR function.
  
  
  METHODS
  Best NPD response to Cl(-)-free and isoproterenol perfusion (=largest ΔPD(0Cl/Iso)) from the right and left nostril was compared to the average result in 13 cystic fibrosis (CF), 78 query-CF patients and 22 healthy controls from 2 cohorts.
  
  
  RESULTS
  Despite moderate to good correlation (p<0.001) between right and left measured ΔPD(0Cl/Iso), we observed large differences in some individuals. A comparison of average versus best ΔPD(0Cl/Iso) showed only moderate agreement (Giessen κ=0.538; Toronto κ=0.607). Averaging ΔPD(0Cl/Iso) showed a lower composite chloride response compared to best ΔPD(0Cl/Iso) and altered diagnostic NPD interpretation in 30 of 113 (27%) subjects.
  
  
  CONCLUSIONS
  The current practice of averaging the NPD results of right and left nostril measurements leads to an underestimation of the individual CFTR function and should be reconsidered.
authors.affiliation: Division of Paediatric Gastroenterology, Hepatology and Nutrition, University of Toronto and Physiology and Experimental Medicine, Research Institute, the Hospital for Sick Children, Toronto, Ontario, Canada. Electronic address: katherine.keenan@sickkids.ca.
authors.forename: Katherine
authors.initials: K
authors.lastname: Keenan
authors.affiliation: Division of Paediatric Gastroenterology, Hepatology and Nutrition, University of Toronto and Physiology and Experimental Medicine, Research Institute, the Hospital for Sick Children, Toronto, Ontario, Canada. Electronic address: Julie.Avolio@sickkids.ca.
authors.forename: Julie
authors.initials: J
authors.lastname: Avolio
authors.affiliation: Department of Pediatrics, Justus-Liebig-University Giessen, Giessen, Germany. Electronic address: claudia.rueckes-nilges@paediat.med.uni-giessen.de.
authors.forename: Claudia
authors.initials: C
authors.lastname: Rueckes-Nilges
authors.affiliation: Department of Medicine, University of Toronto and Division of Respirology and Keenan Research Centre of Li Ka Shing Knowledge Institute St. Michael's Hospital, Toronto, Ontario, Canada. Electronic address: TULLISE@smh.ca.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tullis
authors.affiliation: Division of Paediatric Gastroenterology, Hepatology and Nutrition, University of Toronto and Physiology and Experimental Medicine, Research Institute, the Hospital for Sick Children, Toronto, Ontario, Canada. Electronic address: tanja.gonska@sickkids.ca.
authors.forename: Tanja
authors.initials: T
authors.lastname: Gonska
authors.affiliation: Department of Pediatrics, Justus-Liebig-University Giessen, Giessen, Germany. Electronic address: lutz.naehrlich@paediat.med.uni-giessen.de.
authors.forename: Lutz
authors.initials: L
authors.lastname: Naehrlich
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009297:Nasal Mucosa / Q000378:metabolism*; D010641:Phenotype; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D015415:Biomarkers; D019005:Cystic Fibrosis Transmembrane Conductance Regulator
keywords: Cystic fibrosis; Diagnosis; Nasal potential difference