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

Introduction A 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. Methods Adult 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). Results 27 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). Conclusions Only 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. References Kirton 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 Testing Protocol for Hydrogen/Methane Breath Testing (HMBT) to Assess Small Intestinal Bacterial Overgrowth (SIBO) and Carbohydrate Malabsorption (2019)