Orocaecal transit-time by the H2 method: effects of definitions of caecal entry and test meal

The study compares common variants of the hydrogen breath test to measure oroceacal transit time under different conditions. Definition of caecal entry point rather than procedural parameters were found to be a main variable influencing the test results. Visual assessment still seemed to be the most reliable and valid technique. To overcome its subjectivity and evaluator-dependency, a comprehensive set of rules simulating implicit criteria of expert physicians was defined and compared with commonly used caecal entry assessment rules. Results indicated that: 1) using visual assessment, experts produce highly consistent CE points; 2) caecal entries by the new rule set correlate highly with them, while previously published caecal entry detection methods were poorly correlated with visual assessment; 3) using a semiliquid test meal reduced reliability of all methods, but the new method remained superior; 4) earlier caecal entry detection methods failed completely when early peaks or baseline fluctuations were present; 5) detection of H2 non-producers and of bacterial overgrowth was much more difficult with classical caecal entry definitions than with the new rule-set.