European guideline on indications, performance, and clinical impact of hydrogen and methane breath tests in adult and pediatric patients: European Association for Gastroenterology, Endoscopy and Nutrition, European Society of Neurogastroenterology and Motility, and European Society for Paediatric Gastroenterology Hepatology and Nutrition consensus

Dynamics and metabolic effects of intestinal gases in healthy humans

Many living beings use exogenous and/or endogenous gases to attain evolutionary benefits. We make a comprehensive assessment of one of the major gaseous reservoirs in the human body, i.e., the bowel, providing extensive data that may serve as reference for future studies. We assess the intestinal gases in healthy humans, including their volume, composition, source and local distribution in proximal as well as distal gut. We analyse each one of the most abundant intestinal gases including nitrogen, oxygen, nitric oxide, carbon dioxide, methane, hydrogen, hydrogen sulfide, sulfur dioxide and cyanide. For every gas, we describe diffusive patterns, active trans-barrier transport dynamics, chemical properties, intra-/extra-intestinal metabolic effects mediated by intracellular, extracellular, paracrine and distant actions. Further, we highlight the local and systemic roles of gasotransmitters, i.e., signalling gaseous molecules that can freely diffuse through the intestinal cellular membranes. Yet, we provide testable hypotheses concerning the still unknown effects of some intestinal gases on the myenteric and submucosal neurons.

Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS)

BACKGROUND

There is compelling evidence that microbe-host interactions in the intestinal tract underlie many human disorders, including disorders of gut-brain interactions (previously termed functional bowel disorders), such as irritable bowel syndrome (IBS). Small intestinal bacterial overgrowth (SIBO) has been recognized for over a century in patients with predisposing conditions causing intestinal stasis, such as surgical alteration of the small bowel or chronic diseases, including scleroderma and is associated with diarrhea and signs of malabsorption. Over 20 years ago, it was hypothesized that increased numbers of small intestine bacteria might also account for symptoms in the absence of malabsorption in IBS and related disorders. This SIBO-IBS hypothesis stimulated significant research and helped focus the profession's attention on the importance of microbe-host interactions as a potential pathophysiological mechanism in IBS.

PURPOSE

However, after two decades, this hypothesis remains unproven. Moreover, it has led to serious unintended consequences, namely the widespread use of unreliable and unvalidated breath tests as a diagnostic test for SIBO and a resultant injudicious use of antibiotics. In this review, we examine why the SIBO hypothesis remains unproven and, given the unintended consequences, discuss why it is time to reject this hypothesis and its reliance on breath testing. We also examine recent IBS studies of bacterial communities in the GI tract, their composition and functions, and their interactions with the host. While these studies provide important insights to guide future research, they highlight the need for further mechanistic studies of microbe-host interactions in IBS patients before we can understand their possible role in diagnosis and treatment of patient with IBS and related disorders.

MASLD can cause halitosis by small intestinal bacterial overgrowth

OBJECTIVES

Patients with metabolic dysfunction-associated steatotic liver disease (MASLD) exhibit varying degrees of halitosis. The author speculated that small intestinal bacterial overgrowth (SIBO) might lead to MASLD and subsequent extra-oral halitosis and aimed to test this hypothesis.

METHODS

This retrospective cross-sectional study reviewed 885 extra-oral halitosis patients. Halitosis and exhaled dimethyl sulfide (DMS) were measured by organoleptic score (OLS) (0-5) and OralChroma, respectively. SIBO and MASLD were diagnosed by hydrogen breath test and Fibroscan combined with cardiometabolic criteria.

RESULTS

In this study, 133/885 (15.05%) of the halitosis patients otherwise healthy had MASLD, while 87/133 (65.41%) of the MASLD patients were SIBO-positive. No significant differences were observed in physical parameters such as age, serum biochemical parameters such as lipids, or Fibroscan parameters between the SIBO-positive and SIBO-negative patients. However, the OLS was 4 (interquartile range: 3-4) and exhaled DMS level was 56 (43-75) parts per billion (ppb) in the SIBO-positive patients, significantly greater than 2 (2-3) and 43 (25-51) ppb in the SIBO-negative patients (both p < 0.001). Exhaled hydrogen levels positively correlated with the OLS and exhaled DMS levels (r = 0.774, r = 0.740, both p < 0.001).

CONCLUSION

MASLD can cause halitosis by SIBO.

Small Intestinal Bacterial Overgrowth (SIBO), a clinically overdiagnosed entity?

Small intestinal bacterial overgrowth (SIBO) is a clinical entity recognized since ancient times; it represents the consequences of bacterial overgrowth in the small intestine associated with malabsorption. Recently, SIBO as a term has been popularized due to its high prevalence reported in various pathologies since the moment it is indirectly diagnosed with exhaled air tests. In the present article, the results of duodenal/jejunal aspirate culture testing as a reference diagnostic method, as well as the characteristics of the small intestinal microbiota described by culture-dependent and culture-independent techniques in SIBO, and their comparison with exhaled air testing are presented to argue about its overdiagnosis.

Breath of Health: spectroscopy-based breath test for the detection of SARS-CoV-2

BACKGROUND

Nucleic acid amplification tests (NAAT) are considered the gold standard for COVID-19 diagnosis. These tests require professional manpower and equipment, long processing and swab sampling which is unpleasant to the patients. Several volatile organic compounds (VOCs) have been identified in the breath of COVID-19 patients. Detection of these VOCs using a breath test could help rapidly identify COVID-19 patients.

OBJECTIVE

Assess the accuracy of 'Breath of Health' (BOH) COVID-19 Fourier-transform infra-red (FTIR) Spectroscopy-based breath test.

METHODS

Breath samples from patients with or without symptoms suggestive for COVID-19 who had NAAT results were collected using Tedlar bags and were blindly analysed using BOH FTIR spectroscopy. BOH Measures several VOCs simultaneously and differentiating positive and negative results. BOH results were compared to NAAT results as gold standard.

RESULTS

Breath samples from 531 patients were analysed. The sensitivity of BOH breath test was found to be 79.5% and specificity was 87.2%. Positive predictive value (PPV) was 74.7% and negative predictive value (NPV) 90.0%. Calculated accuracy rate was 84.8% and area under the curve 0.834. Subgroup analysis revealed that the NPV of patients without respiratory symptoms was superior over the NPV of symptomatic patients (94.7% vs 80.7%, P-value < 0.0001) and PPV of patients with respiratory symptoms outranks the PPV of individuals without symptoms (85.3% vs 69.2%, P-value 0.0196).

CONCLUSION

We found BOH COVID-19 breath test to be a patient-friendly, rapid, non-invasive diagnostic test with high accuracy rate and NPV that could efficiently rule out COVID-19 especially among individuals with low pre-test probability.

The Molecular Biological Mechanism of Hydrogen Therapy and Its Application in Spinal Cord Injury

Hydrogen, which is a novel biomedical molecule, is currently the subject of extensive research involving animal experiments and in vitro cell experiments, and it is gradually being applied in clinical settings. Hydrogen has been proven to possess anti-inflammatory, selective antioxidant, and antiapoptotic effects, thus exhibiting considerable protective effects in various diseases. In recent years, several studies have provided preliminary evidence for the protective effects of hydrogen on spinal cord injury (SCI). This paper provides a comprehensive review of the potential molecular biology mechanisms of hydrogen therapy and its application in treating SCI, with an aim to better explore the medical value of hydrogen and provide new avenues for the adjuvant treatment of SCI.

Fructose malabsorption and fructan malabsorption are associated in patients with irritable bowel syndrome

BACKGROUND

Food malabsorption and intolerance is implicated in gastrointestinal symptoms among patients with irritable bowel syndrome (IBS). Key triggers include fructose and fructan. Prior studies examined fructose and fructan malabsorption separately in IBS patients. None have concurrently assessed both within the same patient group. We aimed to investigate the association between fructose and fructan malabsorption in the same patients with IBS using hydrogen breath testing (HBT).

METHODS

We retrospectively identified patients with IBS who underwent fructose and fructan HBTs and abstracted their results from the electronic medical record. Fructose and fructan HBTs were performed by administering a 25 g fructose solution or 10 g fructan solution, followed by breath hydrogen readings every 30 min for 3 h. Patients were positive for fructose or fructan malabsorption if breath hydrogen levels exceeded 20 ppm.

RESULTS

Of 186 IBS patients, 71 (38.2%) were positive for fructose malabsorption and 91 (48.9%) were positive for fructan malabsorption. Of these patients, 42 (22.6%) were positive for fructose malabsorption and fructan malabsorption. Positive fructose HBT readings were significantly associated with positive fructan HBT readings (p = 0.0283). Patients positive for fructose malabsorption or fructan malabsorption had 1.951 times higher odds of testing positive for the other carbohydrate.

CONCLUSIONS

Our results reveal a clinically significant association between fructose malabsorption and fructan malabsorption in patients with IBS. Fructan malabsorption should be assessed in patients with fructose malabsorption, and vice versa. Further studies are required to identify the mechanisms underlying our findings.

Glucose breath test for the detection of small intestine bacterial overgrowth: Impact of diet prior to the test

BACKGROUND

Glucose breath test (GBT) is used for the diagnosis of small intestine bacterial overgrowth. A restrictive diet without fibers and/or fermentable food is recommended on the day before the test. The aim of our retrospective study was to evaluate the impact of two different restrictive diets on the results of GBT.

METHODS

A change of the pretest restrictive diet was applied in our lab on September 1, 2020. The recommended diet was a fiber-free diet before this date, and a fiber-free diet plus restriction of all fermentable food afterward. We thus compared the results of GBT performed before (group A) and after (group B) this pretest diet modification. Demographics, reasons to perform GBT, digestive symptoms, and hydrogen and methane baseline values and variations after glucose ingestion were compared between the two groups.

KEY RESULTS

269 patients underwent GBT in group A, and 316 patients in group B. The two groups were comparable in terms of demographics. Methane and hydrogen baseline values were significantly higher in group A (respectively 14 [18] vs. 8 [14] ppm, p < 0.01 and 11 [14] vs. 6 [8] ppm, p < 0.01). The percentage of positive tests was higher in group A for methane (43% vs. 28%, p < 0.05), and for hydrogen (18% vs. 12%, p = 0.03).

CONCLUSION & INFERENCES

This retrospective study suggests the importance of the restrictive diet prior to GBT. A strict limitation of fibers and fermentable food decreased hydrogen and methane baseline values, and the prevalence of positive GBT. Thus a strict restrictive diet should be recommended on the day before the test, in order to limit the impact of food on hydrogen and methane breath levels, and possibly improve the diagnosis quality of GBT.

Comparison of jejunal aspirate culture and methane and hydrogen breath test in the diagnosis of small intestinal bacterial overgrowth

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is still difficult to diagnose. Quantitative culture of small intestine aspirate is recommended to be the gold standard. The methane and hydrogen breath tests are easily repeatable, sufficiently sensitive and highly specific for SIBO diagnosis. Our goal is to contrast the diagnostic value of the breath tests with jejunal aspiration cultures.

METHODS

40 adult outpatients (age < 60) were enrolled in our study. Randomly, within 2 days, both the methane and the hydrogen breath test and jejunal aspiration culture were performed on each patient and the results of both tests were evaluated and contrasted.

RESULTS

The jejunal culture was positive (105CFU / mL) in 14/40(35%) subjects, the lactulose breath test (LBT) was positive in 18/40 (45%) subjects, and the glucose breath test (GBT) was positive in 12/40 (30%). The GBT showed good agreement (κ = 0.659) and LBT showed poor agreement (κ = 0.588) with the jejunal aspirate culture. The sensitivity, specificity, positive and negative predictive values of LBT/GBT were 85.7/71.4%,76.9/92.3%, 66.6/83.3% and 90.9/85.7%, respectively.

CONCLUSIONS

35% of patients with suspected SIBO are identified using jejunal aspirate cultures. For the identification of SIBO, GBT is more specific than LBT, but has a lower sensitivity. In individuals with suspected SIBO, the breath test should be initially due to its good agreement with the jejunal aspirate culture.

Efficacy and safety of a new low-volume PEG with citrate and simethicone bowel preparation for pediatric elective colonoscopy: Phase 3 RCT

Background and study aims Currently available polyethylene glycol (PEG)-based preparations continue to represent a challenge in children. The aim of this study was to compare the efficacy and safety of a new low-volume PEG preparation with a conventional PEG-electrolyte solution (PEG-ES) in children and adolescents. Patients and methods This was a multicenter, randomized, observer-blind, parallel-group, phase 3 clinical trial, where patients were randomized between PMF104 (Clensia) and a conventional PEG-ES (Klean-Prep), and stratified by age stratum (2 to <6; 6 to < 12;12 to <18 years). The primary endpoint was to test the non-inferiority of PMF104 versus PEG-ES, in terms of colon cleansing. Safety, tolerability, acceptability, palatability, and compliance were also assessed. Efficacy endpoints were analyzed in the per protocol set (PPS) and full analysis set (FAS) and safety and tolerability endpoints in the safety set (SAF). Results Of the 356 patients enrolled, 258 were included in the PPS, 346 in the FAS, and 351 in the SAF. Non-inferiority of PMF104 was confirmed for children aged > 6 years and for all age groups in PPS and FAS, respectively. Optimal compliance was reported more frequently in the PMF104 than in the PEG-ES group, in both PPS (86.1% vs. 68.4%) and FAS (82.9% vs. 65.3%). Both preparations were equally safe and tolerable. Palatability and acceptability were considered better in the PMF104 group than in the PEG-ES group (27.1% vs. 15.3% and 15.3% vs. 3.5%, respectively). Conclusions In children aged 6 to 17 years, the new low-volume product PMF104 is non-inferior to the reference PEG-ES in terms of bowel cleansing, safety, and tolerability, with slightly better results in compliance, palatability, and acceptability.

Nonallergic Diseases Associated With Foods

Clinicians are faced with evaluating real and alleged reactions to foods that may be allergic or nonallergic. Pathogenesis, diagnosis, and treatment of various non-IgE-mediated diseases are discussed in this review. These food-related conditions range from mild to severe. Referral for an allergy workup may be pursued despite the lack of IgE-mediated symptoms. Diagnostic testing is available for defined non-IgE-mediated food diseases that are either immunologic or nonimmunologic. These include celiac disease and related disorders, carbohydrate maldigestion, pancreatic insufficiency, and histamine intolerance. In contrast, there is a paucity of definitive studies to prove food intolerance diseases. There are no definitive diagnostic criteria or testing for nonceliac gluten sensitivity. Functional gastrointestinal disorders, such as irritable bowel syndrome, are better stratified diagnostically but still lack reliable testing. Both nonceliac gluten sensitivity and irritable bowel syndrome are linked to dietary triggers including fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Therefore, dietary alteration alone may be diagnostic and therapeutic when all other conditions are ruled out. These conditions are important considerations when evaluating a patient with history of a food reaction. There is little evidence that foods are causative in other ailments such as acne, migraines, and nasal congestion and hypersecretion.

Defining Small Intestinal Bacterial Overgrowth by Culture and High Throughput Sequencing

BACKGROUND& AIMS

Despite accelerated research in small intestinal bacterial overgrowth (SIBO), questions remain regarding optimal diagnostic approaches and definitions. Here, we aim to define SIBO using small bowel culture and sequencing, identifying specific contributory microbes, in the context of gastrointestinal symptoms.

METHODS

Subjects undergoing esophagogastroduodenoscopy (without colonoscopy) were recruited and completed symptom severity questionnaires. Duodenal aspirates were plated on MacConkey and blood agar. Aspirate DNA was analyzed by 16S ribosomal RNA and shotgun sequencing. Microbial network connectivity for different SIBO thresholds and predicted microbial metabolic functions were also assessed.

RESULTS

A total of 385 subjects with <103 colony forming units (CFU)/mL on MacConkey agar and 98 subjects with ≥103 CFU/mL, including ≥103 to <105 CFU/mL (N = 66) and ≥105 CFU/mL (N = 32), were identified. Duodenal microbial α-diversity progressively decreased, and relative abundance of Escherichia/Shigella and Klebsiella increased, in subjects with ≥103 to <105 CFU/mL and ≥105 CFU/mL. Microbial network connectivity also progressively decreased in these subjects, driven by the increased relative abundance of Escherichia (P < .0001) and Klebsiella (P = .0018). Microbial metabolic pathways for carbohydrate fermentation, hydrogen production, and hydrogen sulfide production were enhanced in subjects with ≥103 CFU/mL and correlated with symptoms. Shotgun sequencing (N = 38) identified 2 main Escherichia coli strains and 2 Klebsiella species representing 40.24% of all duodenal bacteria in subjects with ≥103 CFU/mL.

CONCLUSIONS

Our findings confirm ≥103 CFU/mL is the optimal SIBO threshold, associated with gastrointestinal symptoms, significantly decreased microbial diversity, and network disruption. Microbial hydrogen- and hydrogen sulfide-related pathways were enhanced in SIBO subjects, supporting past studies. Remarkably few specific E coli and Klebsiella strains/species appear to dominate the microbiome in SIBO, and correlate with abdominal pain, diarrhea, and bloating severities.

Refractory Hypothyroidism: Unraveling the Complexities of Diagnosis and Management

INTRODUCTION

Refractory hypothyroidism (RH) represents a challenge in the diagnosis and treatment within the field of thyroidology. It is defined as the inability to achieve disease control despite using levothyroxine (LT4) doses of 1.9 μg/kg/d or higher.

METHODS

A comprehensive review, encompassing 103 articles, was conducted using the Scielo, Scopus, and EMBASE databases, providing an approach to evaluation and diagnosis of this condition.

RESULTS

LT4 disintegrates and dissolves within an acidic gastric environment before being absorbed in the jejunum and ileum. It then extensively binds to serum transporter proteins and undergoes deiodination to yield tri-iodothyronine, the biologically active hormone. There are various nonpathological causes of RH, such as noncompliance with treatment, changes in the brand of LT4, food and drug interferences, as well as pregnancy. Pathological causes include lactose intolerance, Helicobacter pylori infection, giardiasis, among others. The diagnosis of RH involves conducting a thorough medical history and requesting relevant laboratory tests to rule out causes of treatment resistance. The LT4 absorption test allows for the identification of cases of malabsorption. The treatment of RH involves identifying and addressing the underlying causes of noncompliance or malabsorption. In cases of pseudomalabsorption, supervised and weekly administration of LT4 may be considered.

DISCUSSION

Early recognition of RH and correction of its underlying cause are of utmost importance, as this avoids the use of excessive doses of LT4 and prevents cardiovascular and bone complications associated with this condition.

The role of hydrogen therapy in Alzheimer's disease management: Insights into mechanisms, administration routes, and future challenges

Alzheimer's disease (AD) is a progressive neurodegenerative disorder predominantly affecting the elderly. While conventional pharmacological therapies remain the primary treatment for AD, their efficacy is limited effectiveness and often associated with significant side effects. This underscores the urgent need to explore alternative, non-pharmacological interventions. Oxidative stress has been identified as a central player in AD pathology, influencing various aspects including amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, mitochondrial dysfunction, and synaptic dysfunction. Among the emerging non-drug approaches, hydrogen therapy has garnered attention for its potential in mitigating these pathological conditions. This review provides a comprehensively overview of the therapeutic potential of hydrogen in AD. We delve into its mechanisms of action, administration routes, and discuss the current challenges and future prospects, with the aim of providing valuable insights to facilitate the clinical application of hydrogen-based therapies in AD management.

Lactose malabsorption and intolerance: What is the correct management in older adults?

Lactose malabsorption is a very common condition due to intestinal lactase deficiency. Post weaning, a genetically programmed and irreversible reduction of lactase activity occurs in the majority of the world's population. Lactose malabsorption does not necessarily result in gastrointestinal symptoms, i.e. lactose intolerance, which occurs in approximately one third of those with lactase deficiency. In the absence of well-established guidelines, the common therapeutic approach tends to exclude milk and dairy products from the diet. However, this strategy may have serious nutritional disadvantages. Mainly in particular categories, such as the older adults, the approach to lactose malabsorption may deserve careful considerations. Milk and dairy products are an important supply of a wide range of nutrients that contribute to meet the nutritional needs in different life stages. Dietary composition can significantly impact the mechanisms leading to age-related loss of bone mineral density, skeletal muscle mass or function and overall risk of sarcopenia. Moreover, in the latest years, different lines of evidence have highlighted an association between dairy intake and prevention of chronic diseases as well as all-cause mortality. The aim of this opinion paper is to provide an overview of lactose malabsorption and intolerance in the older adults and their implications in clinical practice.

Myths and Facts about Food Intolerance: A Narrative Review

Most adverse reactions to food are patient self-reported and not based on validated tests but nevertheless lead to dietary restrictions, with patients believing that these restrictions will improve their symptoms and quality of life. We aimed to clarify the myths and reality of common food intolerances, giving clinicians a guide on diagnosing and treating these cases. We performed a narrative review of the latest evidence on the widespread food intolerances reported by our patients, giving indications on the clinical presentations, possible tests, and dietary suggestions, and underlining the myths and reality. While lactose intolerance and hereditary fructose intolerance are based on well-defined mechanisms and have validated diagnostic tests, non-coeliac gluten sensitivity and fermentable oligosaccharide, disaccharide, monosaccharide, and polyol (FODMAP) intolerance are mainly based on patients' reports. Others, like non-hereditary fructose, sorbitol, and histamine intolerance, still need more evidence and often cause unnecessary dietary restrictions. Finally, the main outcome of the present review is that the medical community should work to reduce the spread of unvalidated tests, the leading cause of the problematic management of our patients.

A personalized management approach in disorders of the irritable bowel syndrome spectrum

Symptoms of the disorders across the irritable bowel syndrome (IBS) spectrum include several different, usually postprandial, abdominal complaints. Up to date, dietary treatments of the IBS have neither been personalized nor diagnosed with sufficient scientific evidence. They have mostly been treated using 'one-size-fits-all' approaches. Such include exclusion diets, a low fermentable oligosaccharides, disaccharides, monosaccharides and polyols diet, and gluten-free diets, lactose-free diets, a diet recommended by the UK National Institute for Health and Care Excellence, and a wheat-free diet. The exact pathophysiology of IBS disorders across the spectrum is still unclear. However, the symptom profile of IBS spectrum disorders seems similar to that of food intolerance/malabsorption syndromes. Celiac disease, fructose malabsorption, histamine intolerance and lactose intolerance represent food intolerance/malabsorption disorders based on the indigestion of sugars and/or proteins. Helicobacter pylori infection may potentially promote the development of IBS and, when facing a case of IBS-like symptoms, a search for intolerance/malabsorption and H. pylori should be added to find the correct treatment for the respective patient. This review will discuss why the 'one-size-fits-all' dietary approach in the treatment of complaints across the IBS spectrum cannot be successful. Hence, it will provide an overview of the most common overall dietary approaches currently used, and why those should be discouraged. Alternatively, a noninvasive diagnostic workup of the pathophysiologic factors of food intolerance/malabsorption in each patient with symptoms of the IBS spectrum is suggested. Additionally, if H. pylori is found, eradication therapy is mandatory, and if food intolerance/malabsorption is detected, an individual and personalized dietary intervention by a registered dietician is recommended.

Changes in the negative logarithm of end-tidal hydrogen partial pressure indicate the variation of electrode potential in healthy Japanese subjects

Molecular hydrogen (H2) is produced by human colon microbiomes and exhaled. End-tidal H2 sampling is a simple method of measuring alveolar H2. The logarithm of the hydrogen ion (H+)/H2 ratio suggests the electrode potential in the solution according to the Nernst equation. As pH is defined as the negative logarithm of the H+ concentration, pH2 is defined as the negative logarithm of the H2 effective pressure in this study. We investigated whether changes in pH2 indicated the variation of electrode potential in the solution and whether changes in end-tidal pH2 could be measured using a portable breath H2 sensor. Changes in the electrode potential were proportional to ([Formula: see text]) in phosphate-buffered solution (pH = 7.1). End-tidal H2 was measured in the morning (baseline) and at noon (after daily activities) in 149 healthy Japanese subjects using a handheld H2 sensor. The median pH2 at the baseline was 4.89, and it increased by 0.15 after daily activities. The variation of electrode potential was obtained by multiplying the pH2 difference, which suggested approximately + 4.6 mV oxidation after daily activities. These data suggested that changes in end-tidal pH2 indicate the variation of electrode potential during daily activities in healthy human subjects.

Prevalence, risk factors, and treatment of small intestinal bacterial overgrowth in children

Small intestinal bacterial overgrowth (SIBO) is defined as the presence of an excessive number of bacteria within the small bowel. Pediatric SIBO is a heterogeneous disorder that manifests as various symptoms ranging from mild gastrointestinal symptoms to malabsorption or malnutrition. The carbohydrate breath test is a commonly used, safe, and noninvasive diagnostic test; however, a standardized methodology is lacking. Multiple factors, such as neuromuscular disorders, systemic diseases, chronic drug use, or altered intestinal anatomy that disturb intestinal motility or induce an abnormality in the body's defense systems against intestinal bacteria, predispose children to SIBO. The high prevalence and similar symptoms of SIBO in functional gastrointestinal disorders, including irritable bowel syndrome, suggest an association between them. The principles of treatment include managing predisposing conditions, nutritional support, symptom control, and antibacterial treatment. Rifaximin is the most commonly used drug. To date, studies of antibiotic treatment in pediatric populations with irritable bowel syndrome or SIBO are lacking and have shown mixed results. Here we review the prevalence, diagnostic tests, and treatment results in pediatric populations.

Low prevalence of positive hydrogen breath tests in patients with functional gastrointestinal conditions and hypermobile Ehlers-Danlos syndrome

BACKGROUND

Using hydrogen breath testing (HBT) to diagnose small intestinal bacterial overgrowth (SIBO) remains controversial in patients with functional gastrointestinal (GI) disorders, and unknown in those with hypermobility Ehlers-Danlos syndrome (hEDS). We assessed prevalence of positive HBTs in these groups, evaluated the predictive value of GI symptoms and the potential role of proton pump inhibitors (PPIs) on test results.

METHODS

Sequential patients referred for HBT to a tertiary unit were classified into the following groups: GI maldigestion/malabsorption, GI sensorimotor disorders, hEDS, and functional GI disorders. All underwent standardized HBT, and the yield was assessed against symptoms and PPI use.

KEY RESULTS

A total of 1062 HBTs were performed over 3 years (70% female, mean age 48 ± 16 years). Overall, 7.5% (80/1062) patients had a positive HBT. Prevalence of positive HBT was highest in patients with GI maldigestion/malabsorption (17.9%; DOR 16.16, p < 0.001), GI sensorimotor disorders (15.9%; DOR 8.84, p < 0.001), compared to functional GI disorders (1.6%; DOR 1.0) (p < 0.0001). None of the hEDS patients tested positive for HBT. A positive HBT was independently associated with increased age (DOR 1.03; p < 0.001) and symptoms of diarrhea (DOR 3.95; p < 0.0001). Patients on PPIs tended towards a positive HBT than patients off PPIs (16.1% vs 6.9%; DOR 2.47; p < 0.0001).

CONCLUSIONS & INFERENCES

Less than 2% of patients with functional GI disorders, and none of the patients with hEDS had a positive HBT. Pre-test probability was higher in patients with: GI structural or neurological disorders; use of long-term PPIs and symptoms of diarrhea. These criteria may be helpful in making appropriate therapeutic decisions and avoiding unnecessary hydrogen breath testing.

A Comprehensive Look at the -13910 C>T LCT Gene Polymorphism as a Molecular Marker for Vitamin D and Calcium Levels in Young Adults in Central and Eastern Europe: A Preliminary Study

Intolerance to dairy products resulting from the abnormal digestion of milk sugar (lactose) is a common cause of human gastrointestinal disorders. The aim of this study was to show that the -13910 C>T LCT gene polymorphism, together with genotypes of selected VDR gene polymorphisms and diet and nutritional status parameters, can impact the prevalence of vitamin D and calcium deficiency in young adults. This study was conducted on a group of 63 people, which comprised 21 individuals with primary adult lactase deficiency, and a control group of 42 individuals with no hypolactasia. The LCT and VDR gene genotypes were assessed using PCR restriction fragment length polymorphism (PCR-RFLP) analysis. A validated HPLC method was used to determine serum concentrations of 25(OH)D₂ and 25(OH)D₃. Atomic absorption spectrometry was used to determine calcium levels. Their diets (self-reported 7-day estimated food record), estimated calcium intakes based on the ADOS-Ca questionnaire and basic anthropometric parameters were assessed. The CC genotype associated with hypolactasia was found in 33.3% of the subjects. The presence of the CC variant of the LCT gene polymorphism in the study group of young Polish adults was found to be associated with significantly lower milk (134.7 ± 66.7 g/d vs. 342.5 ± 176 g/d; p = 0.012) and dairy product consumption (78.50 ± 36.2 g/d vs. 216.3 ± 102 g/d; p = 0.008) compared with lactase persistence. At the same time, people with adult-type primary intolerance were found to have statistically significant lower serum levels of vitamin D and calcium (p < 0.05). There was a higher chance of vitamin D and calcium deficiency and a lower intake in the group exhibiting lactase non-persistence (OR > 1). The AA variant of the VDR gene's BsmI polymorphism present in people with hypolactasia may further contribute to an increased risk of vitamin D deficiency. Exclusion of lactose from the diet, combined with impaired vitamin D metabolism, may also lead to inhibited calcium absorption by the body. Further research should be carried out on a larger group of subjects to clarify the relationship between lactase activity and vitamin D and calcium levels in young adults.

Prevalence of small intestinal bacterial overgrowth in irritable bowel syndrome (IBS): Correlating H 2 or CH 4 production with severity of IBS

Background and Aim

The prevalence and the role of small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome (IBS) remain unclear, as the literature provides heterogeneous information on the subject. The aim of this study was to determine the prevalence of SIBO in IBS and to assess the correlation between methane and hydrogen levels measured during breath tests and the severity of IBS.

Method

Two-hundred and forty-seven patients with IBS were prospectively included. A glucose breath test (GBT) measured H₂ and CH₄ production to diagnose SIBO. A test was positive when H₂ values exceeded 12 ppm in the first 90 min and/or when a CH₄ value exceeded 10 ppm at any time. IBS severity (IBS-SSS), quality of life (GIQLI), and anxiety and depression (HAD) were assessed to investigate the correlation with H₂ and CH₄ production.

Results

The prevalence of SIBO in IBS was 36.4% (9.7% with H₂, 26.7% with CH₄). CH₄ levels were significantly higher in the predominantly constipated patients (P = 0.00), while H₂ levels were significantly higher within the diarrheal phenotype (P = 0.01). IBS severity was not correlated with either H₂ levels (r = 0.02; P = 0.84) or CH₄ levels (r = 0.05; P = 0.64). H₂ production was inversely correlated with the quality of life (r = -0.24; P = 0.03) and significantly correlated with the HAD scale (r = 0.22; P = 0.03). The pain and discomfort experienced during GBT was not correlated with methane levels (r = -0.09, P = 0.40), hydrogen levels (r = -0.01, P = 0.93), or sum of both (r = 0.06, P = 0.58), but significantly associated with IBS severity (r = 0.50, P <0.00).

Conclusion

SIBO has a high prevalence in IBS but does not increase its severity. Individual susceptibility to pain may have a greater influence on the severity of IBS.

Understanding Our Tests: Hydrogen-Methane Breath Testing to Diagnose Small Intestinal Bacterial Overgrowth

There is increasing appreciation that small intestinal bacterial overgrowth (SIBO) drives many common gastrointestinal symptoms, including diarrhea, bloating, and abdominal pain. Breath testing via measurement of exhaled hydrogen and methane gases following ingestion of a readily metabolized carbohydrate has become an important noninvasive testing paradigm to help diagnose SIBO. However, because of a number of physiological and technical considerations, how and when to use breath testing in the diagnosis of SIBO remains a nuanced clinical decision. This narrative review provides a comprehensive overview of breath testing paradigms including the indications for testing, how to administer the test, and how patient factors influence breath testing results. We also explore the performance characteristics of breath testing (sensitivity, specificity, positive and negative predictive values, likelihood ratios, and diagnostic odds ratio). Additionally, we describe complementary and alternative tests for diagnosing SIBO. We discuss applications of breath testing for research. Current estimates of SIBO prevalence among commonly encountered high-risk populations are reviewed to provide pretest probability estimates under a variety of clinical situations. Finally, we discuss how to integrate breath test performance characteristics into clinical care decisions using clinical predictors and the Fagan nomogram.

Small Intestinal Bacterial Overgrowths and Intestinal Methanogen Overgrowths Breath Testing in a Real-Life French Cohort

INTRODUCTION

Breath testing has become a widely used tool to diagnose small intestinal bacterial overgrowths (SIBOs) and intestinal methanogen overgrowths (IMOs) in clinical settings. Owing to the heterogeneity in clinical manifestations and lack of standardization among centers performing breath testing, SIBO and IMO can be easily overlooked by the clinician. We studied the prevalence and symptoms of SIBO/IMO in French patients referred for breath testing after seeking medical advice.

METHODS

Breath test data and symptoms of 331 patients were assessed for SIBO/IMO using the H 2 /CH 4 lactulose breath test (LBT). Wilcoxon test or χ 2 test were used to compare patients with SIBO/IMO with patients without SIBO/IMO. LBT positive patients (H 2 +, CH 4 +, and CH 4 +/H 2 +) were compared using Kruskal-Wallis test for continuous data or χ 2 test for categorical data.

RESULTS

Among the 186 (68.1%) patients tested positive for an overgrowth with 40.3%, 47.3%, and 12.4% for H 2 +, CH 4 + and CH 4 +/H 2 +, respectively, the presence of diarrhea was significantly increased in hydrogen type overgrowths ( P < 0.001). No significant difference according to age, gender, and symptoms was associated with a positive test except for joint pain that was less prevalent among LBT positive patients ( P = 0.038). In 86.5% of IMOs, positivity with CH 4 values ≥10 ppm could be identified at baseline.

DISCUSSION

There are little discriminating symptoms that can help the clinician to identify patients likely to have a SIBO/IMO. However, SIBO/IMOs remain a common disorder widely underdiagnosed that need further studies to better apprehend functional bowel disorders.

Investigating the association between the symptoms of women with Fibromyalgia, Digestive function, and markers of the microbiota of the Gastrointestinal Tract (The FIDGIT Study): study protocol

BACKGROUND

Fibromyalgia a common idiopathic condition affecting around 1.4% of adults globally. Its signature symptom is chronic widespread pain, with a constellation of somatic and psychological symptoms. Fibromyalgia is associated with significant reductions in quality of life, yet to date there is no biochemical marker for its diagnosis. Previous studies have indicated a strong association with gastrointestinal dysfunction, and more recently, alterations to the gut microbiome. No studies have examined the inter-relationship between fibromyalgia, gastrointestinal dysfunction, and the microbiome. This prospective observational case-controlled study will gather data on gastrointestinal function, dietary intake, fermentation patterns of ingested carbohydrates, and symptoms commonly associated with fibromyalgia. These will be evaluated alongside human gene expression and metatranscriptomic analysis of the oral and faecal microbiome.

METHODS

Adult women aged ≥18 years diagnosed with fibromyalgia and/or meeting ACR 2016 criteria, and healthy family or age-matched controls will be recruited from the community. From consenting participants, we will collect detailed survey information and samples of blood, urine, stool, saliva, and breath.

DISCUSSION

This is the first prospective study examining interactions between digestive function, human gene expression, and the gut microbiome together with general, and fibromyalgia-specific, symptoms experienced by New Zealand women. This exploration will allow an in-depth understanding of clinically relevant factors that are associated with fibromyalgia and will guide further research and contribute to improved management of this poorly understood condition.

TRIAL REGISTRATION

The study was approved by the New Zealand Health and Disability Committee (HDEC) (ref: 20/CEN/197) and registered with the Australia and New Zealand Clinical Trials Registry (ANZCTR), registration number ACTRN12620001337965. Written consent will be obtained after providing participants with detailed information about the procedures. Access to data will be restricted to the immediate research team, and all samples and survey data will be deidentified and coded before analysis.

Diagnosis by Microbial Culture, Breath Tests and Urinary Excretion Tests, and Treatments of Small Intestinal Bacterial Overgrowth

Small intestinal bacterial overgrowth (SIBO) is characterized as the increase in the number and/or alteration in the type of bacteria in the upper gastrointestinal tract and accompanies various bowel symptoms such as abdominal pain, bloating, gases, diarrhea, and so on. Clinically, SIBO is diagnosed by microbial culture in duodenum/jejunum fluid aspirates and/or the breath tests (BT) of hydrogen/methane gases after ingestion of carbohydrates such as glucose. The cultural analysis of aspirates is regarded as the golden standard for the diagnosis of SIBO; however, this is invasive and is not without risk to the patients. BT is an inexpensive and safe diagnostic test but lacks diagnostic sensitivity and specificity depending on the disease states of patients. Additionally, the urinary excretion tests are used for the SIBO diagnosis using chemically synthesized bile acid conjugates such as cholic acid (CA) conjugated with para-aminobenzoic acid (PABA-CA), ursodeoxycholic acid (UDCA) conjugated with PABA (PABA-UDCA) or conjugated with 5-aminosalicylic acid (5-ASA-UDCA). These conjugates are split by bacterial bile acid (cholylglycine) hydrolase. In the tests, the time courses of the urinary excretion rates of PABA or 5-ASA, including their metabolites, are determined as the measure of hydrolytic activity of intestinal bacteria. Although the number of clinical trials with this urinary excretion tests is small, results demonstrated the usefulness of bile acid conjugates as SIBO diagnostic substrates. PABA-UDCA disulfate, a single-pass type unabsorbable compound without the hydrolysis of conjugates, was likely to offer a simple and rapid method for the evaluation of SIBO without the use of radioisotopes or expensive special apparatus. Treatments of SIBO with antibiotics, probiotics, therapeutic diets, herbal medicines, and/or fecal microbiota transplantation are also reviewed.

Berberine and rifaximin effects on small intestinal bacterial overgrowth: Study protocol for an investigator-initiated, double-arm, open-label, randomized clinical trial (BRIEF-SIBO study)

Introduction: Small intestinal bacterial overgrowth (SIBO) leads to non-specific abdominal discomfort and nutrient malabsorption. Currently, rifaximin is widely applied in SIBO based on its antibacterial and non-absorbable nature. Berberine is a natural component of many popular medicine plants that ameliorates intestinal inflammation in humans through its modification of the gut microbiota. Potential effect of berberine to the gut may provide therapeutic target for SIBO. We aimed to evaluate the effect of berberine compared with rifaximin on SIBO patients. Methods: This is an investigator-initiated, single-center, open-label, double-arm randomized controlled trial, termed BRIEF-SIBO (Berberine and rifaximin effects for small intestinal bacterial overgrowth). In total, 180 patients will be recruited and allocated to an intervention group (berberine) and a control group (rifaximin). Each participant will receive one 400 mg drug twice a day (800 mg daily) for 2 weeks. The total follow-up period is 6 weeks from the start of medication. The primary outcome is a negative breath test. The secondary outcomes include abdominal symptom relief and alteration in gut microbiota. Efficacy assessment will be performed every 2 weeks, as well as safety assessment during the treatment. The primary hypothesis is that berberine is not inferior to rifaximin for SIBO. Discussion: The BRIEF-SIBO study is the first clinical trial assessing the eradication effects of 2 weeks of berberine treatment in SIBO patients. The effect of berberine will be fully verified by using rifaximin as the positive control. The findings of this study may have implications for the management of SIBO, especially increasing the awareness of both physicians and patients who are suffering from long-term abdominal discomfort and avoiding excessive examination.

Wireless Monitoring of Gastrointestinal Transit Time, Intra-luminal pH, Pressure and Temperature in Experimental Pigs: A Pilot Study

BACKGROUND

There is no single gold standard for investigation of gastrointestinal motility function. Wireless motility monitoring involves a novel concept which provides a complex information on gastrointestinal function (gastrointestinal transit time, intra-luminal pH, pressure and temperature). Gastrointestinal motility functions of experimental pigs are very similar to those of humans. That is why porcine studies have already provided suitable experimental models for several preclinical projects.

AIMS

The aim of our study was to adopt methods of non-invasive wireless monitoring of gastrointestinal functions in experimental pigs.

METHODS

Five experimental adult female pigs were enrolled into the study. Wireless motility capsules were delivered into the porcine stomach endoscopically. Gastrointestinal transit and intra-luminal conditions were recorded for five days.

RESULTS

Records of animals provided good (3 pigs) or very good quality files (2 pigs). 31150 variables were evaluated. Mean time of the presence of capsules in the stomach was 926 ± 295 min, transfer of a capsule from the stomach into the duodenum lasted 5-34 min. Mean small intestinal transit time was 251 ± 43 min. Food intake was associated with an increase of gastric luminal temperature and a decrease of intra-gastric pressure. The highest intra-luminal pH was present in the ileum. The highest temperature and the lowest intra-luminal pressure were found in the colon. All data displayed a substantial inter-individual variability.

CONCLUSIONS

This pilot study has proven that a long-term function monitoring of the gastrointestinal tract by means of wireless motility capsules in experimental pigs is feasible. However, both ketamine-based induction of general anaesthesia as well as long-lasting general anaesthesia (> 6 hours) should be avoided to prevent retention of a capsule in the porcine stomach.

Breath Tests Used in the Context of Bariatric Surgery

This review article focuses on the use of breath tests in the field of bariatrics and obesitology. The first part of the review is an introduction to breath test problematics with a focus on their use in bariatrics. The second part provides a brief history of breath testing. Part three describes how breath tests are used for monitoring certain processes in various organs and various substances in exhaled air and how the results are analyzed and evaluated. The last part covers studies that described the use of breath tests for monitoring patients that underwent bariatric treatments. Although the number of relevant studies is small, this review could promote the future use of breath testing in the context of bariatric treatments.

Methanogenic archaea in the human gastrointestinal tract

The human microbiome is strongly interwoven with human health and disease. Besides bacteria, viruses and eukaryotes, numerous archaea are located in the human gastrointestinal tract and are responsible for methane production, which can be measured in clinical methane breath analyses. Methane is an important readout for various diseases, including intestinal methanogen overgrowth. Notably, the archaea responsible for methane production are largely overlooked in human microbiome studies due to their non-bacterial biology and resulting detection issues. As such, their importance for health and disease remains largely unclear to date, in particular as not a single archaeal representative has been deemed to be pathogenic. In this Perspective, we discuss the current knowledge on the clinical relevance of methanogenic archaea. We explain the archaeal unique response to antibiotics and their negative and positive effects on human physiology, and present the current understanding of the use of methane as a diagnostic marker.

Bifidobacterium animalis subsp. lactis Bi-07 supports lactose digestion in vitro and in randomized, placebo- and lactase-controlled clinical trials

BACKGROUND

Probiotics may alleviate lactose maldigestion.

OBJECTIVES

The objective was to select a probiotic with high lactase activity and compare it with lactase and placebo in clinical trials.

METHODS

Bacterial cultures were screened for lactase activity in a model of the upper gastrointestinal (GI) tract. Bifidobacterium animalis subsp. lactis Bi-07 (Bi-07) counts were adjusted in subsequent experiments to correspond to 4500 Food Chemicals Codex (FCC) units of lactase, the amount in the European Food Safety Authority (EFSA)-approved health claim. Two crossover clinical trials, Booster Alpha and Booster Omega, were performed in participants with lactose intolerance, where 2 × 1012 CFUs Bi-07, 4662 FCC lactase, or placebo was consumed simultaneously with a lactose challenge, with 1-wk washouts between challenges. The trial designs were identical except for the source of lactose. Breath hydrogen concentration (BHC) was measured to assess the effect of the investigational products on lactose digestion, for which incremental area under the curve (iAUC) was the primary outcome. Peak BHC, cumulative BHC, and GI symptoms were secondary outcomes.

RESULTS

Bi-07 was superior to placebo in reducing BHC [iAUC, parts per million (ppm) ∙ h] in both trials (Booster Alpha: geometric least square mean ratio: 0.462; 95% CI: 0.249, 0.859; P = 0.016; Booster Omega: 0.227; 95% CI: 0.095, 0.543; P = 0.001). Lactase was superior to placebo in Booster Alpha (0.190; 95% CI: 0.102, 0.365; P < 0.001) but not Booster Omega (0.493; 95% CI: 0.210, 1.156; P = 0.102). Noninferiority of Bi-07 compared with lactase was observed in Booster Omega (0.460; 95% CI: 0.193, 1.096; P = 0.079; CI upper limit < 1.25 noninferiority margin). Odds of abdominal pain (compared with placebo: 0.32, P = 0.036) and flatulence (compared with placebo: 0.25, P = 0.007) were lower with lactase in Booster Alpha. Increased odds of nausea were seen with Bi-07 (compared with placebo: 4.0, P = 0.005) in Booster Omega.

CONCLUSIONS

Bi-07 has high lactase activity, and in 2 clinical trials, it supported lactose digestion in individuals with lactose intolerance.These trials were registered at clinicaltrials.gov as NCT03659747 (Booster Alpha) and NCT03814668 (Booster Omega).

Small Intestinal Bacterial Overgrowth-Pathophysiology and Its Implications for Definition and Management

The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that permitted the small bowel to be colonized by potentially injurious colonic microbiota. Such colonization resulted in clinical signs, symptoms, and laboratory abnormalities that were explicable within a coherent pathophysiological framework. Coincident with advances in medical science, diagnostic testing evolved from small bowel culture to breath tests and on to next-generation, culture-independent microbial analytics. The advent and ready availability of breath tests generated a dramatic expansion in both the rate of diagnosis of SIBO and the range of associated gastrointestinal and nongastrointestinal clinical scenarios. However, issues with the specificity of these same breath tests have clouded their interpretation and aroused some skepticism regarding the role of SIBO in this expanded clinical repertoire. Furthermore, the pathophysiological plausibility that underpins SIBO as a cause of maldigestion/malabsorption is lacking in regard to its purported role in irritable bowel syndrome, for example. One hopes that the application of an ever-expanding armamentarium of modern molecular microbiology to the human small intestinal microbiome in both health and disease will ultimately resolve this impasse and provide an objective basis for the diagnosis of SIBO.

Bacterial overgrowth and lactose intolerance: how to best assess

PURPOSE OF REVIEW

To provide an up-to-date review on the clinical assessment of two important gastrointestinal problems with overlapping symptomatology but diverse cause and testing methods. Small intestinal bacterial overgrowth (SIBO) is characterized by the presence of excess bacteria in the small intestine associated with bloating, distention, gas, and diarrhea. Lactose intolerance is caused by lactase enzyme deficiency in the small bowel mucosa leading to lactose malabsorption and symptoms of bloating, gas, and diarrhea.

RECENT FINDINGS

SIBO is assessed by hydrogen/methane breath test using glucose as a substrate and/or small bowel aspirate and culture but these tests have shortcomings. Consequently, several new diagnostic techniques, including novel capsule technologies and other approaches are being evaluated. Lactose intolerance can be assessed by hydrogen/methane breath test using lactose as a substrate, or small bowel mucosal lactase assay, genetic testing and lactose tolerance test, although the efficacy and practicality of these diagnostic modalities are not equal.

SUMMARY

In clinical practice, gas, bloating, distention, pain, and diarrhea are common gastrointestinal symptoms that often remain unexplained when routine gastrointestinal endoscopy, imaging, and stool tests are negative. These patients should be evaluated for SIBO and/or food intolerances including lactose intolerance.

Modification of baseline status to improve breath tests performance

Breath tests used to evaluate carbohydrates malabsorption require baseline H₂ and CH₄ levels as low as possible. Test cancellation is recommended when exceeding certain cut-offs (H₂ ≥ 20 ppm and CH₄ ≥ 10 ppm). Although following preparation protocols, many patients have baseline levels above those cut-offs. We investigated if light walking can reduce baseline H₂ and CH₄ levels. We retrospectively analyzed baseline H₂ and CH₄ levels from 1552 breath tests. Baseline levels (B1), especially in H₂, were lower when obtained at later hours of the day. In those with baseline levels above cut-off, re-sampling (B2) after light walking for one hour, decreased H₂ levels 8 ppm (Q1–Q3: 1–18 ppm), and 2 ppm (Q1–Q3: 0–3 ppm) for CH₄. Consequently, 40% of tests with elevated B1 levels, presented B2 levels below mentioned cut-offs. Ten percent of tests considered negative when using B1 for calculations, turned positive when using B2 instead. All positive tests when using B1 values, remained elevated when using B2. Re-sampling after light walking for one hour could allow test performance in those with previous elevated baseline levels, avoiding diagnosis delays. Using the second sample for delta calculations identifies positive patients for malabsorption that would have been considered negative.

Ultra-sensitive ppb-level methane detection based on NIR all-optical photoacoustic spectroscopy by using differential fiber-optic microphones with gold-chromium composite nanomembrane

In this paper, we propose and experimentally demonstrate an ultra-sensitive all-optical PAS gas sensor, incorporating with a near-infrared (NIR) diode laser, fiber-optic microphones (FOMs) and a double channel differential T-type photoacoustic cell. The FOM is realized by Fabry-Perot interferometry and novel gold-chromium (Au-Cr) composite nanomembranes. To meet the demand of high sensitivity and flat frequency response for the FOMs, the Au-Cr composite diaphragm is deliberately designed and fabricated by E-beam evaporation deposition with 330 nm in thickness and 6.35 mm in radius. Experimental results show that the FOM has a sensitivity of about 30 V/Pa and a flat frequency response from 300 to 900 Hz with fluctuation below 1 dB. Moreover, a double channel differential T-type photoacoustic cell is designed and employed in the all-optical PAS gas sensor, with the first-order resonant frequency of 610 Hz. The all-optical gas sensor is established and verified for CH₄ detection and the normalized noise equivalent absorption (NNEA) is 4.42 × 10^-10 W∙cm^-1∙Hz^-1/2. The minimum detection limit (MDL) of 36.45 ppb is achieved with a 1 s integration time. The MDL could be further enhanced to 4.87 ppb with an integration time of 81 s, allowing ultra-sensitive trace gas detection.

Carbohydrate Maldigestion and Intolerance

This review summarizes dietary carbohydrate intolerance conditions and recent advances on the possible role of carbohydrate maldigestion and dietary outcomes in patients with functional bowel disease. When malabsorbed carbohydrates reach the colon, they are fermented by colonic bacteria, with the production of short-chain fatty acids and gas lowering colonic pH. The appearance of diarrhoea or symptoms of flatulence depends in part on the balance between the production and elimination of these fermentation products. Different studies have shown that there are no differences in the frequency of sugar malabsorption between patients with irritable bowel disease (IBS) and healthy controls; however, the severity of symptoms after a sugar challenge is higher in patients than in controls. A diet low in 'Fermentable, Oligo-Di- and Monosaccharides and Polyols' (FODMAPs) is an effective treatment for global symptoms and abdominal pain in IBS, but its implementation should be supervised by a trained dietitian. A 'bottom-up' approach to the low-FODMAP diet has been suggested to avoid an alteration of gut microbiota and nutritional status. Two approaches have been suggested in this regard: starting with only certain subgroups of the low-FODMAP diet based on dietary history or with a gluten-free diet.

Belgian consensus on irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is characterised by recurrent abdominal pain related to defaecation or associated with altered stool frequency or consistency. Despite its prevalence, major uncertainties in the diagnostic and therapeutic management persist in clinical practice.

METHODS

A Delphi consensus was conducted by 20 experts from Belgium, and consisted of literature review and voting process on 78 statements. Grading of recommendations, assessment, development and evaluation criteria were applied to evaluate the quality of evidence. Consensus was defined as > 80 % agreement.

RESULTS

Consensus was reached for 50 statements. The Belgian consensus agreed as to the multifactorial aetiology of IBS. According to the consensus abdominal discomfort also represents a cardinal symptom, while bloating and abdominal distension often coexist. IBS needs subtyping based on stool pattern. The importance of a positive diagnosis, relying on history and clinical examination is underlined, while additional testing should remain limited, except when alarm features are present. Explanation of IBS represents a crucial part of patient management. Lifestyle modification, spasmolytics and water-solube fibres are considered first-line agents. The low FODMAP diet, selected probiotics, cognitive behavioural therapy and specific treatments targeting diarrhoea and constipation are considered appropriate. There is a consensus to restrict faecal microbiota transplantation and gluten-free diet, while other treatments are strongly discouraged.

CONCLUSIONS

A panel of Belgian gastroenterologists summarised the current evidence on the aetiology, symptoms, diagnosis and treatment of IBS with attention for the specificities of the Belgian healthcare system.

Significance of validated symptom assessment versus breath testing for malabsorption after lactose load in children

BACKGROUND AND OBJECTIVES

Lactose malabsorption and lactose-induced symptoms are poorly correlated, as shown by breath tests and various symptom assessment methods. Validated assessment is the key to overcome the limitations of biased symptom measurements. We characterized lactose-induced symptoms with the population-specific, validated paediatric carbohydrate perception questionnaire (pCPQ) and their correlation with the history of symptoms (HoS).

METHODS

A total of 130 patients with functional gastrointestinal symptoms underwent a lactose hydrogen breath and tolerance test (LBTT) allowing for a diagnosis of malabsorption (M+) and lactose sensitivity (S+). HoS indicative of lactose-induced symptoms (abdominal pain, nausea, bloating, flatulence, diarrhoea) in the 4 weeks preceding the test was determined using a validated questionnaire. The pCPQ was used to score lactose-induced symptoms.

MAIN RESULTS

The LBTT revealed 41 children (31.5%) with lactose malabsorption (M+), 56 (43.1%) with lactose sensitivity (S+) and 24 (18.5%) were M+/S+. Sensitivity correlated with HoS (P < 0.001), regardless of whether malabsorption was detectable. Malabsorption status did not correlate with HoS (NS). The odds of lactose sensitivity significantly increased when abdominal pain [odds ratio (OR) 3.5, confidence interval (CI) 1.6-7.8], nausea (OR 2.3, CI, 1.1-4.9) and flatulence (OR 3.1, CI 1.4-6.8) were reported in the 4 weeks preceding the LBTT. Symptoms after the lactose load were similar for M+/S+ and M-/S+, except for flatulence, which was more frequent in malabsorbers (P < 0.01).

CONCLUSION

Our findings fit well with the emerging view of the important role of a validated symptom assessment after a lactose load. The determination of symptoms may be more relevant than malabsorption for the clinical outcomes of paediatric patients with lactose-related gastrointestinal symptoms.

Lactose Malabsorption and Presumed Related Disorders: A Review of Current Evidence

Background. Lactose malabsorption (LM) is a frequent clinical problem associated with several digestive and extra-digestive diseases. The aim of this manuscript was to clarify the real clinical impact of LM on these disorders. Methods. A literature search for digestive and extra-digestive disorders related to LM was carried out using PubMed, Medline and Cochrane. Results. A transient lactase deficiency is present in celiac disease (CD) on a normal diet. The persistence of symptoms in CD on a gluten-free diet may be instead, in part, attributed to a primary LM. Similar circumstances are present in inflammatory bowel diseases (IBD), in which LM can be responsible for a part of persistent symptoms in IBD on clinical remission. LM and irritable bowel syndrome (IBS) are instead independent conditions. On the other hand, a lactose-restricted diet may be useful for some IBS patients. A reduced lactose intake can lead to low bone mass and limited risk of fragility fractures. Finally, the absorption of levothyroxine could be conditioned by LM. Conclusions. LM can be responsible for persistent symptoms in CD and IBD. The association with IBS seems to be casual. Bone mass and levothyroxine absorption can be affected by LM.

The prevalence of small intestinal bacterial overgrowth in diabetes mellitus: a systematic review and meta-analysis

OBJECTIVE

We conducted this systematic review and meta-analysis to estimate the prevalence of SIBO in diabetic patients and to determine the association between SIBO and diabetes.

METHODS

A comprehensive literature search of the PubMed, Cochrane Library and EMBASE databases from inception to June 2021 was conducted for studies correlating SIBO with diabetes. Studies were screened, and relevant data were extracted and analysed. The pooled prevalence of SIBO among diabetic patients and the odds ratio of SIBO among diabetic patients compared with controls were calculated.

RESULTS

Fourteen studies including 1417 diabetic patients and 649 controls met the inclusion criteria. The pooled prevalence of SIBO in diabetes was 29% (95% CI 20-39%). The odds ratio of SIBO in diabetic patients was 2.91 (95% CI 0.82-10.32, p=0.1) compared with controls. Subgroup analyses showed that the prevalence of SIBO in diabetes was higher in studies using jejunal aspirate culture for diagnosis (39%, 95% CI 12-66%) than in those using the lactulose breath test (31%, 95% CI 18-43%) or glucose breath test (29%, 95% CI 14-43%). The prevalence of SIBO in diabetes was higher in studies conducted in Western countries (35%, 95% CI 21-49%) than in those conducted in Eastern countries (24%, 95% CI 14-34%), and the prevalence of SIBO in type 1 diabetes (25%, 95% CI 14%-36%) was not significantly different from that in type 2 diabetes (30%, 95% CI 13%-47%).

CONCLUSIONS

Twenty-nine percent of diabetic patients tested positive for SIBO, and the risk of SIBO in diabetic patients was 2.91 times higher than that in patients without diabetes. Diabetes could be a predisposing factor for the development of SIBO, especially among patients diagnosed by jejunal aspirate culture or those in Western populations.

Delayed Analysis of Hydrogen-Methane Breath Samples

PURPOSE

Hydrogen-methane breath tests are used to diagnose carbohydrate malabsorption and small intestinal bacterial overgrowth. The COVID-19 pandemic has driven the modification of procedures as breath tests are potentially aerosol-generating procedures. We assessed the effect of delayed analysis of breath samples, facilitating the at-home performance of breath testing.

METHODS

Children provided two breath samples at every step of the lactose breath test. The samples were brought back to the clinic, and one set of samples was analyzed immediately. The second set was stored at room temperature and analyzed 1-4 days later.

RESULTS

Out of the 73 "double" lactose breath tests performed at home, 33 (45.8%) were positive. The second samples were analyzed 20 to 117 hours after the first samples (41.7±24.3 hours). There was no significant difference in the hydrogen concentration between the first and second sets (Z=0.49, p=0.62). This was not the case for methane, which had a significantly higher concentration in the second breath samples (Z=7.6).

CONCLUSION

Expired hydrogen levels remain stable in plastic syringes if preserved at room temperature for several days. On the other hand, the delayed analysis of methane appeared to be less reliable. Further research is needed to examine the impact of delayed analysis on methane and hydrogen concentrations.