title: Bravo catheter-free pH monitoring: normal values, concordance, optimal diagnostic thresholds, and accuracy.
abstract: OBJECTIVE
  The Bravo pH capsule is a catheter-free intraesophageal pH monitoring system that avoids the discomfort of an indwelling catheter. The objectives of this study were as follows: (1) to obtain normal values for the first and second 24-hour recording periods using a Bravo capsule placed transnasally 5 cm above the upper border of the lower esophageal sphincter determined by manometry and to assess concordance between the 2 periods, (2) to determine the optimal discriminating threshold for identifying patients with gastroesophageal reflux disease (GERD), and (3) to validate this threshold and to identify the recording period with the greatest accuracy.
  
  
  METHODS
  Normal values for a manometrically positioned, transnasally inserted Bravo capsule were determined in 50 asymptomatic subjects. A test population of 50 subjects (25 asymptomatic, 25 with GERD) then was monitored to determine the best discriminating thresholds. The thresholds for the first, second, and combined (48-hour) recording periods then were validated in a separate group of 115 patients.
  
  
  RESULTS
  In asymptomatic subjects, the values measured using a manometrically positioned Bravo pH capsule were similar between the first and second 24-hour periods of recording. The highest level of accuracy with Bravo was observed when an abnormal composite pH score was obtained in the first or second 24-hour period of monitoring.
  
  
  CONCLUSIONS
  Normal values for esophageal acid exposure were defined for a manometrically positioned, transnasally inserted, Bravo pH capsule. An abnormal composite pH score, obtained in either the first or second 24-hour recording period, was the most accurate method of identifying patients with GERD.
authors.affiliation: Department of Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Shahin
authors.initials: S
authors.lastname: Ayazi
authors.forename: John C
authors.initials: JC
authors.lastname: Lipham
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Portale
authors.forename: Christian G
authors.initials: CG
authors.lastname: Peyre
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Streets
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Leers
authors.forename: Steven R
authors.initials: SR
authors.lastname: Demeester
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Banki
authors.forename: Linda S
authors.initials: LS
authors.lastname: Chan
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hagen
authors.forename: Tom R
authors.initials: TR
authors.lastname: Demeester
mesh_terms: D053704:Capsule Endoscopy / Q000379:methods*; D050782:Esophageal pH Monitoring; D004947:Esophagus / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012016:Reference Values; D013997:Time Factors