Establishing Normal Values For Gastrointestinal Hydrogen Sulphide Production in Breath Using Selected-Ion Flow-Tube Mass Spectrometry (SIFT-MS)
A Hobson1,2,3, S Bloor1,2,3, N Nagalingam4, A Smolinska4, B O’Brien4, R Stallard4, T Woodland4, A Tawfike4, M Allsworth4, B Boyle4
1. Functional Gut Diagnostics
2. The Functional Gut Clinic
3. Anglia Ruskin University
4. Owlstone Medical
Introduction: Hydrogen and methane breath testing is well established in terms of analysis techniques, guidelines for test preparation and clinical cut-offs allowing for the diagnosis of Small Intestinal Bacterial Overgrowth (SIBO), Intestinal Methanogen Overgrowth (IMO) and carbohydrate malabsorption. Hydrogen sulphide (H2S) is another by-product of microbial fermentation that is produced under anaerobic conditions by sulphur reducing gut microbes that can impact gut motility and inflammation. Increased H2S production has been associated with symptoms of diarrhoea and gastrointestinal disorders such as IBD and IBS. Until recently, current techniques for measuring H2S reported values in the parts per million (ppm) range which may not be sensitive enough to detect pathological changes. In this study we use SIFT-MS which can detect H2S in the parts per billion (ppb) range to establish normative values.
Methods: 25 healthy volunteers completed a 3hr lactulose breath test using standard test preparation guidelines. Breath samples were taken at baseline (0 mins) and 45, 90 and 180-minutes post lactulose ingestion. Samples were collected using 500ml polyvinylidene fluoride (PVDF) bags and analysed using SIFT-MS. This was repeated at 28 days post iron supplementation.
Results: H2S values on visit 1 demonstrated levels in the parts per billion range (mean H2S = 20 ppb ±5) at baseline and this did not change in response to lactulose ingestion (p=0.62). After 28 days of iron supplementation (visit 2) the amount of H2S produced at baseline decreased significantly (p=0.027) but no further differences were seen post lactulose. Hydrogen and Methane gases were also measured to confirm intestinal fermentation of the test substrate
Conclusions: We demonstrate that in healthy subjects H2S can be reliably detected in the ppb range using SIFT-MS. Breath samples remains stable within PVDF bags at up to 7-days post acquisition making this a viable technique for in clinic or home testing. The lack of response to lactulose ingestion in this study may reflect the low prevalence of H2S production from the healthy microbiome. Further studies in patients with IBD and IBS are now warranted to establish the pathological range of H2S production.