PWE-081 Hydrogen breath testing: high incidence of small Intestinal bacterial overgrowth diagnosis using lactulose versus glucose

Background A hydrogen breath test is an inexpensive, non-invasive and safe diagnostic test used to investigate intestinal disorders, including suspected Small Intestinal Bacterial Overgrowth (SIBO). The recent publication of the North American Consensus statement1 suggests a rise ≥20 ppm of hydrogen within 90 min as an ideal threshold for a positive test to suggest the presence of SIBO following ingestion of glucose or lactulose. As lactulose is a non-digestible disaccharide, it is possible that such a rise during a lactulose test is due to fermentation in the colon, rather than an indicator of SIBO. A small retrospective audit was undertaken to investigate how many patients with a positive lactulose test for SIBO had a subsequent positive glucose test. Methods Adult patients who had previously attended for a lactulose hydrogen breath test which established the presence of hydrogen-producing bacteria and met the diagnostic criteria for SIBO were included in this audit. All patients attended for a glucose hydrogen breath test within 6 weeks of their lactulose breath test, and had not received antibiotic therapy during this time period. After a baseline reading, patients provided a breath-hydrogen sample every 15 min for 60 min post ingestion of a glucose solution. Further breath hydrogen samples were then taken every 30 min for 180 min. Results were analysed to determine the number of patients who met the diagnostic criteria for SIBO (≥20 ppm rise in hydrogen above baseline within 180 min). Results 18 patients (11F, 7M) were included in this small audit. 2 patients (F) were found to be positive for SIBO, whereas 16 patients (9F, 7M) were concluded to be negative, as they did not demonstrate a significant rise in expired hydrogen (≥20 ppm above baseline) within 180 min. 11.1% of patients included in this audit had SIBO confirmed with a glucose hydrogen breath test, despite all having a positive lactulose test using the criteria suggested in the North American Consensus paper. Conclusion Based on the lactulose results alone, the majority of patients in this audit (88.9%) would have been reported as having a SIBO, despite a negative glucose test. Using lactulose alone as a substrate to diagnose SIBO may therefore provide a false positive result, potentially leading to misdiagnosis and inappropriate use of antibiotics. Reference Rezaie A, et al. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. The American journal of gastroenterology. 2017;112(5):77–4.