Influence of the substrate on the reproducibility of the hydrogen breath test to measure the orocecal transit time

Background: The H-2 breath test is widely used for the measurement of the orocecal transit time (OCTT). However, its clinical applicability is limited by its suboptimal reproducibility. Aim: To investigate whether changes in the substrate for the H-2 breath lest 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 H-2 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). Conclusion: The meal substrate influences the variability of the OCTT. However, reproducibility of the test does not improve with the addition of a liquid meal.