title: An international randomized multicenter comparison of nasal potential difference techniques.
abstract: BACKGROUND
  The transepithelial nasal potential difference (NPD) is used to assess cystic fibrosis transmembrane conductance regulator (CFTR) activity. Unreliability, excessive artifacts, and lack of standardization of current testing systems can compromise its use as a diagnostic test and outcome measure for clinical trials.
  
  
  METHODS
  To determine whether a nonperfusing (agar gel) nasal catheter for NPD measurement is more reliable and less susceptible to artifacts than a continuously perfusing nasal catheter, we performed a multicenter, randomized, crossover trial comparing a standardized NPD protocol using an agar nasal catheter with the same protocol using a continuously perfusing catheter. The data capture technique was identical in both protocols. A total of 26 normal adult subjects underwent NPD testing at six different centers.
  
  
  RESULTS
  Artifact frequency was reduced by 75% (P < .001), and duration was less pronounced using the agar catheter. The measurement of sodium conductance was similar between the two catheter methods, but the agar catheter demonstrated significantly greater CFTR-dependent hyperpolarization, because Δ zero Cl- + isoproterenol measurements were significantly more hyperpolarized with the agar catheter (224.2 ± 12.9 mV with agar vs 18.2 ± 9.1 mV with perfusion, P < .05).
  
  
  CONCLUSIONS
  The agar nasal catheter approach demonstrates superior reliability compared with the perfusion nasal catheter method for measurement of NPD. This nonperfusion catheter method should be considered for adoption as a standardized protocol to monitor CFTR activity in clinical trials.
authors.affiliation: University of Alabama at Birmingham, Birmingham, AL 35294-0006, USA.
authors.forename: George M
authors.initials: GM
authors.lastname: Solomon
authors.forename: Michael W
authors.initials: MW
authors.lastname: Konstan
authors.forename: Michael
authors.initials: M
authors.lastname: Wilschanski
authors.forename: Joanne
authors.initials: J
authors.lastname: Billings
authors.forename: Isabelle
authors.initials: I
authors.lastname: Sermet-Gaudelus
authors.forename: Frank
authors.initials: F
authors.lastname: Accurso
authors.forename: François
authors.initials: F
authors.lastname: Vermeulen
authors.forename: Elina
authors.initials: E
authors.lastname: Levin
authors.forename: Heather
authors.initials: H
authors.lastname: Hathorne
authors.forename: Ginger
authors.initials: G
authors.lastname: Reeves
authors.forename: Gina
authors.initials: G
authors.lastname: Sabbatini
authors.forename: Aubrey
authors.initials: A
authors.lastname: Hill
authors.forename: Nicole
authors.initials: N
authors.lastname: Mayer-Hamblett
authors.forename: Melissa
authors.initials: M
authors.lastname: Ashlock
authors.forename: John Paul
authors.initials: JP
authors.lastname: Clancy
authors.forename: Steven M
authors.initials: SM
authors.lastname: Rowe
mesh_terms: D000328:Adult; D000362:Agar; D000704:Analysis of Variance; D016477:Artifacts; D002404:Catheterization / Q000379:methods*; D018592:Cross-Over Studies; D003550:Cystic Fibrosis / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D005260:Female; D005782:Gels; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D009297:Nasal Mucosa / Q000502:physiology*
chemical_list: D005782:Gels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000362:Agar
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