Links between celiac disease and small intestinal bacterial overgrowth: A systematic review and meta-analysis

Background and Aim Symptoms of small intestinal bacterial overgrowth (SIBO) and celiac disease (CeD) often overlap, and studies suggest a link between SIBO and CeD. We thus conducted a systematic review and meta-analysis to compare SIBO prevalence in CeD patients and controls and assessed effects of antimicrobial therapy on gastrointestinal symptoms in SIBO positive CeD patients. Methods Electronic databases were searched until February 2022 for studies reporting SIBO prevalence in CeD. Prevalence rates, odds ratio (OR), and 95% confidence intervals (CI) of SIBO in CeD and controls were calculated. Results We included 14 studies, with 742 CeD patients and 178 controls. The pooled prevalence of SIBO in CeD was 18.3% (95% CI: 11.4-28.1), with substantial heterogeneity. Including case-control studies with healthy controls, SIBO prevalence in CeD patients was significantly increased (OR 5.1, 95% CI: 2.1-12.4, P = 0.0001), with minimal heterogeneity. Utilizing breath tests, SIBO prevalence in CeD patients was 20.8% (95% CI: 11.9-33.7), almost two-fold higher compared with culture-based methods at 12.6% (95% CI: 5.1-28.0), with substantial heterogeneity in both analyses. SIBO prevalence in CeD patients nonresponsive to a gluten free diet (GFD) was not statistically higher as compared with those responsive to GFD (OR 1.5, 95% CI: 0.4-5.0, P = 0.511). Antibiotic therapy of SIBO positive CeD patients resulted in improvement in gastrointestinal symptoms in 95.6% (95% CI: 78.0-99.9) and normalization of breath tests. Conclusions This study suggests a link between SIBO and CeD. While SIBO could explain nonresponse to a GFD in CeD, SIBO prevalence is not statistically higher in CeD patients non-responsive to GFD. The overall quality of the evidence is low, mainly due to substantial "clinical heterogeneity" and the limited sensitivity/specificity of the available diagnostic tests.