title: 13C urea breath test with nondispersive isotope-selective infrared spectrometry: reproducibility and importance of the fasting status.
abstract: BACKGROUND
  The 13C urea breath test (13C-UBT) is the most convenient method for diagnosing Helicobacter pylori infection noninvasively. Nondispersive isotope-selective infrared spectrometry (NDIRS) is an inexpensive and easy alternative to mass spectrometry. The objective of this study was to evaluate: (1) the reproducibility of the 13C-UBT as performed by using the NDIRS method; (2) the repeatability of bags analysis and the impact of delayed analysis; and (3) the need for fasting status for the 13C-UBT.
  
  
  METHODS
  The 13C-UBT was performed with 75 mg urea labeled with 13C, with breath samples collected at times 0 and 30 minutes. Results are expressed as delta over baseline (0/00). Fifty-three patients underwent two successive 13C-UBTs with an interval of 48 to 72 hours. The 106 collected bags were randomly reanalyzed immediately or 72 hours later. In 26 volunteer subjects, the 13C-UBT was performed both in a fasting condition and after a nonstandardized meal. The reproducibility was assessed by the method of Bland and Altman.
  
  
  RESULTS
  The mean of difference between two successive tests was 0. 14 0/00 (standard deviation, 0.90), and the coefficient of repeatability was 1.80 (confidence interval, 95%). The difference between two successive analyses was always less than 2.2% of the initial value. The coefficient of variation between two successive tests for the influence of a meal was 11.24.
  
  
  CONCLUSIONS
  The 13C-UBT as performed by using NDIRS is reproducible, analyses can be delayed up to 72 hours, and the test must be performed in fasting conditions.
authors.affiliation: Department of Gastroenterology, Ziekenhuis-Vrije Universiteit Brussel, Belgium. gasmaf@az.vub.ac.be
authors.forename: F
authors.initials: F
authors.lastname: Mana
authors.forename: P R
authors.initials: PR
authors.lastname: Franken
authors.forename: H R
authors.initials: HR
authors.lastname: Ham
authors.forename: H
authors.initials: H
authors.lastname: Reynaert
authors.forename: D
authors.initials: D
authors.lastname: Urbain
mesh_terms: D001944:Breath Tests / Q000379:methods*; D002247:Carbon Isotopes; D005215:Fasting / Q000502:physiology; D005260:Female; D016481:Helicobacter Infections / Q000175:diagnosis* / Q000503:physiopathology; D016480:Helicobacter pylori; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014508:Urea
chemical_list: D002247:Carbon Isotopes; D014508:Urea