Small intestinal bacterial overgrowth in irritable bowel syndrome: systematic review and meta-analysis.

BACKGROUND & AIMS: Small intestinal bacterial overgrowth (SIBO) has been proposed as an etiologic factor in irritable bowel syndrome (IBS), but evidence is conflicting. We conducted a systematic review and meta-analysis of the prevalence of SIBO in IBS.

METHODS: MEDLINE and EMBASE were searched up to November 2008. Case series and case-control studies applying diagnostic tests for SIBO in unselected adults meeting diagnostic criteria for IBS were eligible. Prevalence of a positive test for SIBO was extracted and pooled for all studies, and compared between cases and controls using an odds ratio and 95% confidence interval (CI).

RESULTS: Twelve studies were identified containing 1921 subjects meeting criteria for IBS. Pooled prevalence of a positive lactulose or glucose hydrogen breath test was 54% (95% CI, 32%-76%) and 31% (95% CI, 14%-50%), respectively, with statistically significant heterogeneity between study results. Prevalence of a positive jejunal aspirate and culture was 4% (95% CI, 2%-9%). The pooled odds ratio for any positive test for SIBO in cases compared with healthy asymptomatic controls was 3.45 (95% CI, 0.9-12.7) or 4.7 (95% CI, 1.7-12.95), depending on the criteria used to define a positive test, with statistically significant heterogeneity for both.

CONCLUSIONS: Prevalence of SIBO in individuals meeting diagnostic criteria for IBS was highest with breath testing. The prevalence in cases with IBS compared with controls varied according to criteria used to define a positive test. The role of testing for SIBO in individuals with suspected IBS remains unclear.