The prevalence of small intestine bacterial overgrowth in irritable bowel syndrome is much higher with lactulose than glucose breath test: Results of a retrospective monocentric study

Background

Glucose (GBT) and lactulose (LBT) breath tests have been recommended for the diagnosis of small intestinal bacterial overgrowth (SIBO). LBT may yield a higher prevalence of SIBO diagnosis, because of its limited small bowel absorption, and therefore colonic fermentation. The aim of this retrospective study was to confirm this hypothesis, in irritable bowel syndrome patients (IBS).

Methods

Among a cohort of 995 patients who underwent GBT or LBT, 287 with typical IBS according to Rome IV criteria, without past digestive surgery or significant medical comorbidities, were included.

Results

155 IBS patients underwent GBT, and 132 LBT (71% women, mean age 45±15, mean BMI: 22.6±4.3 kg/m²). There were no difference between both groups in terms of demographics, IBS type and severity of symptoms. The prevalence of SIBO according to LBT was 47%, versus 4.5% only with GBT (p<0.001). The prevalence of methane values ≥ 10 ppm were similar in both groups (34%).

Conclusion

LBT is very frequently positive in IBS patients, as compared to GBT. The 2 tests are thus not interchangeable for the diagnosis of SIBO. Furthermore, the positivity of both tests was not correlated with symptoms, which may indicate a poor clinical interest of these tests in IBS.