Fasting breath hydrogen concentrations in gastric and small-intestinal bacterial overgrowth

Although elevated fasting breath hydrogen concentrations have been reported in small-intestinal bacterial overgrowth, this diagnosis has been presumptive or based on definitions that vary from study to study. The influence of gastric bacterial overgrowth and gastroduodenal pH has not been documented. Conflicting evidence exists as to the reproducibility of breath hydrogen measurements.

Forty-two subjects underwent culture of gastric and duodenal aspirates. The pH was measured by indicator paper. Paired fasting breath hydrogen concentrations were measured by gas chromatography within 7 days of endoscopy.

Paired fasting breath hydrogen concentrations differed in terms of normality or abnormality in 21% of subjects. Paired concentrations correlated significantly in overgrowth but not in culture-negative subjects. Sensitivity for bacterial overgrowth was 4-29%, and specificity 71-100%. No correlation with gastroduodenal pH was found.

The clinical relevance of a single fasting breath hydrogen concentration is limited. The efficacy of paired measurements for gastric or small-intestinal bacterial overgrowth is poor.