title: Influence of the substrate on the reproducibility of the hydrogen breath test to measure the orocecal transit time.
abstract: BACKGROUND
  The H2 breath test is widely used for the measurement of the orocecal transit time (OCTT). However, its clinical applicability is limited by its suboptimal reproducibility.
  
  
  OBJECTIVE
  To investigate whether changes in the substrate for the H2 breath test improve its reliability for the measurement of the OCTT.
  
  
  METHODS
  72 consecutive patients referred for measurement of the OCTT were studied. The breath test was performed twice, on consecutive days. One group of patients ('lactulose + water' group) received lactulose 13.3 g in water both days. Another group ('lactulose + diet') received lactulose 13.3 g in a liquid meal of 400 kcal. A third group ('lactulose-lactitol') received 13.2 g of lactulose the first day and 10 g lactitol the following day. The fourth group ('lactitol + water') received lactitol 10 g in water both days. Alveolar breath was sampled every 10 min for the next 3 h for H2 chromatography.
  
  
  RESULTS
  OCTT in the first and second day test for the groups 'lactulose + water', 'lactulose + diet' and 'lactitol + water' were similar. In these three groups, the values obtained on the first and second day did not differ from 0 and were also significantly correlated. However, the correlation and the mean coefficient of variation were better in group 'lactulose + water' than in the groups 'lactulose + diet' and 'lactitol + water'. In group 'lactulose-lactitol' the results on both days were significantly correlated although the delta between matched values was different from 0 (p = 0.03).
  
  
  CONCLUSIONS
  The meal substrate influences the variability of the OCTT. However, reproducibility of the test does not improve with the addition of a liquid meal.
authors.affiliation: Digestive System Research Unit, Hospital General Vall d'Hebron, Barcelona, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Casellas
authors.forename: J
authors.initials: J
authors.lastname: Malagelada
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D001944:Breath Tests; D002400:Cathartics / Q000494:pharmacology*; D004032:Diet; D005260:Female; D005772:Gastrointestinal Transit / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D006859:Hydrogen; D007792:Lactulose / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013402:Sugar Alcohols / Q000494:pharmacology*
chemical_list: D002400:Cathartics; D013402:Sugar Alcohols; D007792:Lactulose; D006859:Hydrogen; C014635:lactitol