Evaluation of small intestinal bacterial overgrowth

Introduction: There has been phenomenal interest concerning gut microbiota dysbiosis including small intestinal bacterial overgrowth (SIBO). However, the diagnostic methods for SIBO are still unsatisfactory.

Areas covered: The current review covers the different invasive and noninvasive tests to diagnose SIBO, their methodology, interpretation, sensitivity, specificity, and limitations based on the selected articles from literature search using searchterms 'small intestinal bacterial overgrowth' AND 'digestive diseases' OR'diagnosis' OR 'hydrogen breath test' in PubMed in December 2022. The current review will cover some potential methods for diagnosis of SIBO that may be of clinical utility in the future.

Expert opinion: SIBO was conventionally defined as a total bacterial count >10⁵ colony forming units (CFU) per mL on quantitative culture of upper gut aspirate. The threshold for the diagnosis of SIBO has been reduced to >10³CFU per mL of aspirate recently. Considering the invasiveness of collecting upper gut aspirate, need for laboratory infrastructure and manpower to culture it, noninvasive hydrogen breath tests (HBT) became popular. However, due to the poor sensitivity and specificity of HBT to diagnose SIBO, their utility is being challenged. A new technology of measuring intra-luminal hydrogen gas has a potential to bring a paradigm shift in the diagnostic tests for SIBO.