Prevalence and consistency of low breath H2 excretion following lactulose ingestion - Possible implications for the clinical use of the H2 breath test

The clinical use of the H₂ breath test is limited by the finding that a variable fraction of the population fails to excrete appreciable H₂ during colonic carbohydrate fermentation. Therefore, we assessed the ability to increase breath H₂ excretion in 371 patients (224 female, 147 male) by administering the nonabsorbable sugar lactulose. Following 12 g of lactulose, 27% of 94 patients did not increase their breath H₂ concentration over 20 ppm and were considered low H₂ excretors. Ingestion of 20 g of lactulose in 277 patients yielded a frequency of low H₂ excretors of 14%. Six of 10 patients that were low H₂ excretors after 12 g of lactulose increased their breath H₂ levels over 20 ppm when tested with 20 g. In 35 patients tested with the same amount of lactulose on two separate occasions, the subject frequently altered his or her H₂ producing status over a period of a few weeks. Low H₂ excretors had a significantly higher breath CH₄ concentration, both fasting (22 ± 34 ppm) and after lactulose (51 ± 58 ppm) compared to the remaining patients (5 ± 13 ppm and 16 ± 40 ppm, respectively). While the mean age of low excretors (54 ± 17 years) was significantly higher than the others (44 ± 17 years), no difference was found for sex prevalence and stool pH. This study demonstrates that respiratory H₂ excretion following lactulose ingestion is not consistent and suggests that the application of too restrictive criteria could lead to improper interpretation of the H₂ breath test.