The characteristics of the positivity to the lactulose breath test in patients with abdominal bloating

OBJECTIVES: The clinical utility in patients with bloating is still conflicting. We aimed to evaluate the positivity to lactulose breath test (LBT) in patients with bloating, and to assess the clinical characteristics according to the positivity or subtypes of LBT. METHODS: The patients with abdominal bloating undergoing LBT were investigated. Rome III positive irritable bowel syndrome (IBS) and bowel symptoms were surveyed according to the positivity or subtypes of LBT. RESULTS: The prevalence of IBS and the positivity to LBT was 23.8% (86 of 358) and 29.6% (106 of 358), respectively. The positivity to LBT and the prevalence in subtypes of LBT were not different according to the presence of IBS. The subtypes of LBT positive (+) patients were LBT (H ₂) with 61 (57.5%), (CH ₄)+ with 30 (28.3%), and (both) positive with 15 (14.2%). The LBT (H ₂)+ group was younger, and had higher symptomatic score for the bloating than that in the LBT negative (-) group. The LBT (CH ₄)+ group was older, and had higher scores of hard stool and strain than those of the LBT (-) group. In the fasting LBT (H ₂)+ group (n=37) diagnosed by increased baseline H ₂, the scores for abdominal discomfort, bloating, and flatus were higher than those for the LBT (H ₂)+ or LBT(-) groups. CONCLUSIONS: The subtypes of the positivity to LBT according to the gas produced or the fasting H ₂ may contribute to specificity or severity of abdominal symptoms regardless of the presence of IBS.