Sarah Bloor & Charlotte Pitcher at the Breath Biopsy Conference 2022
(36 mins) APPLICATIONS OF BREATH ANALYSIS: The past, present, and future of breath testing for bacterial overgrowth
Intestinal bacterial fermentation of undigested foods results in the production of hydrogen, methane and hydrogen sulphide gases. Tests to assess for small intestinal bacterial overgrowth and carbohydrate malabsorption via hydrogen and methane breath testing (HMBT) has been around for numerous years. However, this technique has been subject to scrutiny and as a result, and to standardise breath testing, the North American Consensus for HMBT was released in 2017. This update changed sugar substrate quantities and test duration. We have assessed the impact of these changes on diagnosis and symptoms during the HMBT.
Until recently, hydrogen sulphide gas produced by intestinal bacteria could not be detected. Hydrogen sulphide is produced by sulphate reducing bacteria using the hydrogen from intestinal fermentation and is commonly associated with diarrhoea. Together with Owlstone Medical, Functional Gut have developed a ‘first in the UK’ hydrogen sulphide breath testing method using SIFT-MS.
In this talk we will discuss how the North American Consensus for HMBT has changed the landscape of hydrogen and methane breath testing, and also discuss how we have developed a hydrogen sulphide breath test and a healthy cut off value in a healthy volunteer study.
Charlotte Pitcher has been working at The Functional Gut Group as a Gastrointestinal Physiologist since graduating from the University of Warwick with a degree in Biomedical Science in 2017. Over this time, she has learned a range of techniques to diagnose various functional disorders of the gastrointestinal system. In particular, she has been heavily involved with Hydrogen and Methane Breath Tests, used in the diagnosis of Small Intestinal Bacterial Overgrowth and Carbohydrate Malabsorption. As part of a team, she implemented FGDs first gas chromatography system for analysis of these breath tests, for both private and NHS patients. In order to help improve breath testing protocols, she studied breath test data and published ‘Performance and Interpretation of Hydrogen and Methane Breath Testing Impact of North American Consensus Guidelines’, as well as a review of the effectiveness of home testing kits for SIBO, which she presented recently at the British Society of Gastroenterology conference.
Sarah Bloor is a clinical gastrointestinal physiologist at The Functional Gut Group. She has been a member of Functional Gut for over 4 years where she runs regular patient clinics, performing tests such as oesophageal manometry and 24hr reflux testing, restech, electrogastrography (EGG), and breath testing for small intestinal bacterial overgrowth and lactose and fructose malabsorption. Sarah is also actively involved in many research projects including the development of the next generation of breath tests with research into hydrogen sulphide. She is also currently working towards a PhD in Medical Sciences with Anglia Ruskin University investigating the impact of iron supplements on the gastrointestinal tract with hydrogen and methane breath testing and Owlstone’s VOC breath testing technology. She has been working closely with Owlstone with her PhD project and hopes to have some initial results available to share at the next breath biopsy conference.
Additional Q & A:
- Is there any limitation on tests that are not analysed within 2 weeks?
The two week timeframe is a recommendation based on some research performed by our sister company, looking at the deterioration of gas, particularly CO2 as a measure of sample validity, over two week. For up to two weeks, there was found to be no significant reduction in contents of the breath vials and all samples remained “valid”. The research did not continue beyond 2 weeks, so there is a risk that some gas can leak from the vials causing them to become invalid samples. However, in practice we have not had any issues with this. We have had instances where samples were analysed 3-4 weeks after collection (caused by postal delays), but CO2 contents were high enough that the samples were still valid and no issues seen with analysis.
- I have a question for the H2S test. The speaker tested 10 ppm of H2S. However, a typical level of H2S is 20 ppb. I think the 10 ppm is very far from 20 ppb. I was wondering your idea on my thoughts?
This concentration was used purely because it was already present within the lab and also contained other interested gases within the mixed cylinder – H2, CH4, CO2. At the start the sensitivity of SIFT-MS for H2S was not known, so we wanted to start with something high and more likely to be detected. All patient H2S was detected on ppb level.
- In general, regarding gut health, non-invasive tests via exhaled breath are very very valuable. However, other biomatrices could be interesting as well, such as fecal headspace, which may contain the functional output of the gut microbiota in a more direct manner. Fecal analyses do have a downside that people do not typically like it. How do you value fecal (headspace) analyses?
Fecal analysis isn’t something we have a lot of experience with, but my understanding is that the huge diversity in the microbiome, and thus in faecal samples, even within healthy populations makes it difficult to distinguish a normal variant from pathological, and makes it difficult to determine presence of specific conditions. Faecal analysis is unlikely to be something that would be useful in testing for SIBO or carbohydrate malabsorption, as it is not the presence of certain species that causes these conditions, instead it is inappropriate fermentation, however it could have use identifying the presence of methanogens and hydrogen sulphide producers.
- How are different ethnicites incorporated in the design of experiments?
For studies participants are not selected based on ethnicities. However, if the participant is happy to disclose their ethnicity this is collected. For the diagnosis of SIBO/IMO/CM we do not know a participants ethnicity, so is not used to determine diagnosis. We just use the north American and Ledochowski guidelines.
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