P265 High incidence of positive hydrogen breath tests for small intestinal bacterial overgrowth using lactulose: follow-up

IntroductionA small audit previously conducted within our department and presented at the BSG 20191 questioned the ‘North American Consensus’ recommendation of using a rise in hydrogen of ≥20 ppm within 90 minutes as the positive threshold for Small Intestinal Bacterial Overgrowth (SIBO)2. We previously reported a high positive result rate using lactulose compared to glucose if the rise in hydrogen of ≥20 ppm within 90 minutes was adhered to when lactulose was administered. A follow on audit has been undertaken.MethodsAdult patients attending the GI Physiology department for a glucose hydrogen breath test between April 2019-February 2020 were audited. All patients included in the audit had received a ‘positive’ SIBO test using lactulose (rise within 90 minutes) ≤6 weeks prior. The new AGIP 2019 guidelines were adhered for both tests3. After a baseline sample was taken, 75 g of glucose in 300 mL of water was ingested by the patient. Breath samples were taken every 15 minutes for the first 90 minutes post-ingestion, and then every 30 minutes for at least 120 minutes. Results were analysed to determine the number of patients who met the diagnostic criteria for SIBO (≥20 ppm above the baseline).Results27 patients were included in this audit (19F, 8M). 3 patients (F) were found to be positive for SIBO, and 24 patients (16F, 8M) were found to be negative for SIBO, as there was no significant rise in expired hydrogen (≥20 ppm above baseline within 180 minutes).ConclusionsOnly 11.1% of audited patients were diagnosed with SIBO following a glucose hydrogen breath test, despite a previous ‘positive’ lactulose breath test following the ‘North American Consensus’ recommendation. Interestingly, this is identical to the audit performed last year. The results of these two audits suggest that a lactulose test alone should not be relied upon to diagnose SIBO, due to the high false positive rate, and should be followed by a glucose hydrogen breath test to confirm the suspected diagnosis if a rise in lactulose is seen within 90 minutes.ReferencesKirton E, et al. High incidence of positive hydrogen breath tests for small intestinal bacterial overgrowth using lactulose compared to glucose. Gut 2019;68(Suppl 2):A1–A269.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):775–84.3. Association of Gastrointestinal Physiologists (AGIP) Proposed Standardised Testi