Comparison of an in vitro faecal hydrogen test with the lactulose breath test: assessment of in vivo hydrogen-producing capability in Burmese village children

Summary

In the assessment of carbohydrate malabsorption, it is important to determine if patients with a flat breath hydrogen (H₂) response to an absorbable carbohydrate challenge are capable of producing H₂. We compared the reliability of a rapid faecal incubation system with the lactulose breath test to assess in vivo H₂ production in 64 children. Overall, 70% of subjects were in vivo H₂-producers, with breath H₂ peaks greater than 10 parts per million within 3 h of ingesting 10 g of the non-absorbable disaccharide lactulose. Faecal specimens from the 64 children had a mean (SE) pH of 5.0 (0.077). Faecal homogenates were incubated with lactulose at both the initially measured faecal pH and at neutral pH. In predicting a normal in vivo H₂-producing ability (sensitivity), the faecal H₂ test was correct in only 22% (faecal pH) to 44% (pH 7) of cases. In predicting an abnormal lactulose breath test result (specificity), faecal homogenate analysis was correct in 53% of cases, at both faecal and neutral pH. These findings indicate that the faecal hydrogen test is unsuitable as a screening test for in vivo H₂ production.