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Summary

Background:  Studies assessing the prevalence of small intestinal bacterial overgrowth in irritable bowel syndrome gave contrasting results. Differences in criteria to define irritable bowel syndrome patients and methods to assess small intestinal bacterial overgrowth may explain different results. Moreover, no data exist on small intestinal bacterial overgrowth prevalence in a significant population of healthy non-irritable bowel syndrome subjects.

Aim:  To assess the prevalence of small intestinal bacterial overgrowth by glucose breath test in patients with irritable bowel syndrome symptoms with respect to a consistent control group.

Methods:  Consecutive patients with irritable bowel syndrome according to Rome II criteria were enrolled. The control population consisted of 102 sex- and age-matched healthy subjects without irritable bowel syndrome symptoms. All subjects underwent glucose breath test. A peak of H2 values >10 p.p.m above the basal value after 50 g of glucose ingestion was considered suggestive of small intestinal bacterial overgrowth.

Results:  A total of 65 irritable bowel syndrome patients and 102 healthy controls were enrolled. Positivity to glucose breath test was found in 31% of irritable bowel syndrome patients with respect to 4% in the control group, the difference between groups resulting statistically significant (OR: 2.65; 95% CI: 3.5–33.7, P < 0.00001).

Conclusions:  The present case–control study showed an epidemiological association between irritable bowel syndrome and small intestinal bacterial overgrowth. Placebo-controlled small intestinal bacterial overgrowth-eradication studies are necessary to clarify the real impact of small intestinal bacterial overgrowth on irritable bowel syndrome symptoms.