Relationship between methane production and breath hydrogen excretion in lactose-malabsorbing individuals.

Recent studies have shown reduced breath hydrogen (H2) excretion in methane (CH4)-producing healthy individuals following ingestion of lactulose. This questions the reliability of the breath hydrogen test (BHT) in CH4 excretors, but the relationship between CH4 and H2 excretion in other clinical applications of the BHT is not known. We reviewed BHT results in two groups of subjects: (1) 385 children tested for lactose malabsorption in a hospital setting, and (2) 109 lactose-malabsorbing patients tested with a home kit. The percentage of lactose malabsorbers in group 1 (51%) was the same regardless of CH4-producing status (P = 0.97). The BHT data from group 2 showed a positive correlation (r = 0.6, P < 0.000001) between the magnitude of the rise in CH4 and H2 concentrations, and the H2 excretion curves were significantly higher in the CH4-producing individuals. We conclude that attention to CH4-producing status is not necessary in the interpretation of the lactose BHT.