IMPACT OF THE NORTH AMERICAN CONSENSUS ON HYDROGEN AND METHANE BREATH TESTING FOR SIBO

Introduction The North American Consensus (NAC) document on breath testing published in 2017 was a first attempt to standardise the diagnostic test for small intestinal bacterial overgrowth (SIBO), including two key recommendations in terms of substrate dosing. The recommended use of 10 g lactulose and 75 g glucose differed from many practices in the UK which used 16 g of lactulose and 50 g of glucose previously, therefore we adopted these new dosing parameters and retrospectively compared these data to those acquired in the previous 3 months. Methods Data from 536 patients were analysed and distinguished into subgroups dependent on substrate-10 g lactulose (n=200), 16 g lactulose (n=200), 75 g glucose (n=82) and 50 g glucose (n=54). Unpaired t-tests were used to determine statistical significance of the results. Results Patients in the higher dose groups for glucose and lactulose had significantly more SIBO positive results (as determined by a rise >10 ppm above baseline in hydrogen in 60 min post ingestion) than those in the lower dose groups (lactulose p=0.0279, glucose p=0.0427). There was no significant difference in methane between groups (p>0.05 for both). The change in glucose and lactulose dose did not have any significant effect on number of patients recording symptoms throughout the test (bloating, nausea or abdominal pain) (p>0.05 for both), however recorded severity of bloating was significantly higher in patients administered 16 g lactulose than those administered 10 g (p=0.0415). With the 10 g lactulose dose, patients with a positive SIBO test experienced significantly more bloating and nausea than negative patients (bloating p=0.0467, nausea p=0.0327), but this difference was not observed in the 16 g lactulose group (p>0.05 for both). Symptoms were equivalent in the glucose groups. Conclusions Glucose (75 g) yields a higher proportion of positive results for SIBO than 50 g without an increase in symptoms. As glucose is absorbed in the proximal small bowel these are likely to be true positives. 16 g of lactulose yielded significantly more positive results than 10 g, but as higher lactulose doses have been shown to reduce intestinal transit time it is possible that these may represent false positive test for SIBO. This is supported by the fact that 16 g of lactulose induced equivalent symptoms in SIBO positive and negative patients whereas 10 g only increased symptoms in SIBO positive patients. These findings broadly support the parameters outlined in the NAC document for SIBO testing.