Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus

The development of next-generation sequencing technology has enabled researchers to explore and understand the gut microbiome from a broader and deeper perspective. However, the results of different studies on gut microbiota are highly variable even in the same disease, which makes it difficult to guide clinical diagnosis and treatment. The ideal sampling method should be non-invasive, involve little cross-contamination or bowel preparation, and collect gut microbiota at different sites. Currently, sequencing technologies are usually based on samples collected from feces, mucosal biopsy, intestinal fluid, etc. However, different parts of the gastrointestinal tract possess various physiological characteristics that are essential for particular species of living microbiota. Moreover, current sampling methods are somewhat defective. For example, fecal samples are just a proxy for intestinal microbiota, while biopsies are invasive for patients and not suitable for healthy controls. In this review, we summarize the current sampling methods and their advantages and shortcomings. New sampling technologies, such as the Brisbane Aseptic Biopsy Device and the intelligent capsule, are also mentioned to inspire the development of future precise description methods of the gut microbiome.

/pdf/current-sampling-methods-for-gut-microbiota-a-call-for-more-2bdt9kk90a.pdf

Current Sampling Methods for Gut Microbiota: A Call for More Precise Devices.

ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth.

Chronic diarrhoea is a common problem, hence clear guidance on investigations is required. This is an updated guideline from 2003 for the investigations of chronic diarrhoea commissioned by the Clinical Services and Standards Committee of the British Society of Gastroenterology (BSG). This document has undergone significant revision in content through input by 13 members of the Guideline Development Group (GDG) representing various institutions. The GRADE system was used to appraise the quality of evidence and grading of recommendations.

https://gut.bmj.com/content/gutjnl/67/8/1380.full.pdf

Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition.

Despite growing literature characterizing the fecal microbiome and its association with health and disease, few studies have analyzed the microbiome of the small intestine. Here, we examine what is known about the human small intestinal microbiota in terms of community structure and functional properties. We examine temporal dynamics of select bacterial populations in the small intestine, and the effects of dietary carbohydrates and fats on shaping these populations. We then evaluate dysbiosis in the small intestine in several human disease models, including small intestinal bacterial overgrowth, short-bowel syndrome, pouchitis, environmental enteric dysfunction, and irritable bowel syndrome. What is clear is that the bacterial biology, and mechanisms of bacteria-induced pathophysiology, are enormously broad and elegant in the small intestine. Studying the small intestinal microbiota is challenged by rapidly fluctuating environmental conditions in these intestinal segments, as well as the complexity of sample collection and bioinformatic analysis. Because the functionality of the digestive tract is determined primarily by the small intestine, efforts must be made to better characterize this unique and important microbial ecosystem.

The Structure and Function of the Human Small Intestinal Microbiota: Current Understanding and Future Directions.

BackgroundThe diagnosis of small intestinal bacterial overgrowth (SIBO) remains challenging. Our aim was to examine the diagnostic yield of duodenal aspiration/culture and glucose breath test (GBT), and effects of gender, race and demographics on prevalence of SIBO.MethodsPatients with unexp

Small intestinal bacterial overgrowth: duodenal aspiration vs glucose breath test.

Dear Sir, We would like to thank Mooney et al. for their interest in our paper. The authors also share their experience of Glucose Breath Test (GBT) for small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome (IBS). Their data indicate an underestimation of SIBO prevalence especially in IBS diarrheapredominant (IBS-D) with the use of GBT. In our study, we tested the prevalence of SIBO with GBT in adult patients with unexplained gastrointestinal (GI) symptoms such as gas, bloating, diarrhea, and abdominal discomfort. We used 75 g glucose as the test dose rather than 50 g in Mooney et al. and we also utilize a set of criteria that are based on our previous data and experience to establish a positive test for GBT. Using these criteria, GBT was positive in 38/ 139 (27.3%) of our subjects but when ≥12 ppm increase was used as the threshold cut-off for H2, GBT was positive in 44/139 (31.7%). In previous studies performed in IBS patients, GBT was found to be positive in 31% of patients when 50 g glucose was used and >12 ppm increase of H2 over baseline was considered positive, and Lactulose Breath Test was positive in 34.3–84%. The prevalence and diagnostic yield of SIBO varies in literature depending on the dose of testing substrate, type of substrate, thresholds used to define a positive breath test, patient characteristics and analysis of breath samples for H2 only or a combination of H2 and CH4. Mooney et al. provided data from their retrospective study comparing two groups of patients; Group 1, all patients that underwent GBT and Group 2, patients with symptoms consistent with IBS-D. From data of Mooney et al., 22.3% of all patients were tested positive with GBT, whereas 19.3% of patients in the IBS-D group was positive with GBT. Similar to our study, Mooney et al. measured both H2 and CH4. 1 However, the authors did not exclude patients with a history of previous GI surgeries that may increase prevalence of SIBO and whether patients discontinued medications that may affect the intestinal motility at least 1 week prior GBT was not stated. Mooney et al. has used 50 g oral glucose as test dose that is lower than the dose in our study. A lower substrate dose of glucose could mean less availability of substrate for bacterial fermentation, as since glucose is avidly absorbed from the proximal small bowel, possibly causing an underestimation of SIBO. Given the fact they had lower yield of GBT despite a lower cut-off (≥10 ppm increase above baseline for H2 or CH4) in a highly susceptible population means that the substrate they used was low and they missed patients. It is highly likely that their yield will be even lower if they used the higher threshold of ≥20 ppm for H2 increase in their study. Using different thresholds to define a positive GBT is a problem and this prevents standardization of GBT testing which discourages direct comparison of studies and the real prevalence of SIBO may be overor under-estimated. Although we believe that ≥20 ppm increase over the baseline for H2 is the appropriate cut-off, further validation studies from others are clearly needed and will help the standardization of GBT.

Possible underestimation of SIBO in IBS patients: is lack of Glucose Breath Test standardization responsible?

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Small intestinal bacterial overgrowth: duodenal aspiration vs glucose breath test.

Possible underestimation of SIBO in IBS patients: is lack of Glucose Breath Test standardization responsible?