Positive glucose breath testing is more prevalent in patients with IBS-like symptoms compared with controls of similar age and gender distribution

J Clin Gastroenterol. 2009 Nov-Dec;43(10):962-6. doi: 10.1097/MCG.0b013e3181a099a5.


Background: Small intestinal bacterial overgrowth (SIBO) may mimic a functional disorder such as irritable bowel syndrome (IBS) or functional bloating (FB). In this study, we aimed to assess the utility of glucose breath test (GBT) in patients with the above conditions.

Methods: This study included 200 consecutive patients (130 with IBS and 70 with FB on the basis of Rome III criteria) and 70 controls with similar age and sex distribution. Patients and controls underwent 50 g GBT and a H2 peak of > or = 12 ppm was considered diagnostic of SIBO. Positive patients received rifaximin of 1200mg/day for 10 days and underwent a second GBT 1 month after the end of treatment. A symptom questionnaire was completed before and after therapy.

Results: GBT resulted to be altered in 21 out of 130 IBS patients and in 2 out of 70 FB patients with a significant difference of the former group compared with controls (3 out of 70, P=0.0137). Most IBS patients with a positive GBT complained of diarrhea. GBT showed an increased methane excretion in 26% of patients, who were equally distributed among different bowel pattern subgroups. Previous abdominal surgery was more frequently seen in GBT-positive patients (P=0.008). After antibiotic treatment, eradication of SIBO was achieved in 70% of patients, with a significant improvement of symptoms in eradicated patients compared with the not eradicated ones (P<0.001).

Conclusions: GBT is useful to identify a subgroup of IBS-like patients, whose symptoms are owing to SIBO. Normalization of GBT after antibiotic therapy is associated with a significant improvement of symptoms. GBT does not offer any advantage in FB patients.

MeSH terms

  • Adult
  • Anti-Bacterial Agents / therapeutic use
  • Breath Tests / methods
  • Female
  • Gastric Dilatation / diagnosis*
  • Gastric Dilatation / microbiology
  • Glucose
  • Humans
  • Intestine, Small / microbiology*
  • Irritable Bowel Syndrome / diagnosis*
  • Irritable Bowel Syndrome / microbiology
  • Male
  • Methane / metabolism
  • Middle Aged
  • Rifamycins / therapeutic use
  • Rifaximin
  • Surveys and Questionnaires


  • Anti-Bacterial Agents
  • Rifamycins
  • Glucose
  • Rifaximin
  • Methane