Small intestinal bacterial overgrowth as an uncommon cause of false positive lactose hydrogen breath test among patients with diarrhea-predominant irritable bowel syndrome in Asia

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.

Efficacy of incremental loads of cow’s milk as a treatment for lactose malabsorption in Japan

BACKGROUND

Lactose intolerance (LI) is commonly seen in East Asian countries. Several studies showed that lactose or milk loading has been used as a treatment for lactose malabsorption (LM) in Western countries, but there have been no reports regarding this type of treatment in Japan. As lactose or milk loading requires ingestion of large amounts of lactose within a short period, this is considered to be too harsh for Japanese people because of their less habitual milk consumption (175 mL per day in average) than Western people. In this study, we demonstrated lactose tolerance acquisition in a suitable way for Japanese.

AIM

To examine the efficacy of lactose (cow’s milk) loading treatment in patients with LM.

METHODS

Individuals with abdominal symptoms induced by milk or dairy products (LI symptoms) were identified with a questionnaire. A 20 g lactose hydrogen breath test (LHBT) was carried out to confirm LM diagnosis and to evaluate co-existence of small intestinal bacterial overgrowth (SIBO). Respondents diagnosed with LM were selected as study subjects and were treated with incremental loads of cow’s milk, starting from 30 mL and increasing up to 200 mL at 4-7 d intervals. After the treatment, changes in symptoms and LM diagnostic value of 20 g LHBT were investigated. Stool samples pre- and post-treatment were examined for changes in intestinal microbiota using 16S rRNA sequencing. Informed consent was obtained prior to each stage of the study.

RESULTS

In 46 subjects with LI symptoms (10-68 years old, mean age 34 years old) identified with the questionnaire, 35 (76.1%) were diagnosed with LM by 20 g LHBT, and 6 had co-existing SIBO. The treatment with incremental cow’s milk was carried out in 32 subjects diagnosed with LM (14-68 years old, median age 38.5 years old). The mean period of the treatment was 41 ± 8.6 d. Improvement of symptoms was observed in 29 (90.6%; 95% confidence interval: 75.0%-98.0 %) subjects. Although 20 g LHBT indicated that 10 (34.5%) subjects had improved diagnostic value of LM, no change was observed in 16 (55.2%) subjects. Analysis of the fecal intestinal microbiota showed a significant increase in Blautia in 7 subjects who became symptom-free after the treatment (P = 0.0313).

CONCLUSION

LM was diagnosed in approximately 75% of the subjects who had LI. Incremental loads of cow’s milk is regarded as a useful treatment for LM without affecting everyday life.

Early hydrogen excretion peaks during breath tests. Small intestinal bacterial overgrowth or accelerated transit?

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) has been reported with varying prevalence, depending upon the criteria used for diagnosis. Lactulose and glucose breath tests are the most used in clinical settings. Early rises of hydrogen excretion during a lactose breath test suggest SIBO, but the finding could result from accelerated mouth-to-caecum transit time.

AIMS

Defining the prevalence of early hydrogen peaks during lactose breath tests and assessing the proportion of patients affected by SIBO.

METHODS

An early (≤ 60') hydrogen excretion peak was observed in 120/663 patients with positive lactose hydrogen breath test. Eighty-one of them underwent a 50 g-9sample-glucose hydrogen breath test to diagnose SIBO.

RESULTS

The glucose breath test proved positive in 11/81 (13.6%) patients. The positivity rate was 18.2% (2/11) in those with the first peak detected at 30' and 12.8% (9/70) in those with the peak occurring at 60'.

CONCLUSIONS

Early hydrogen excretion peaks are rarely associated with SIBO. The low positive predictive value indicates that the finding does not help identifying patients at high risk for this condition. Indirectly, the present data support the opinion that the prevalence of SIBO diagnosed by standard lactulose breath tests is much lower than reported, and the reliability of the test is low.

Relevance of Methane and Carbon Dioxide Evaluation in Breath Tests for Carbohydrate Malabsorption in a Paediatric Cohort

OBJECTIVES

The relevance of methane measurement in breath tests for the detection of carbohydrate malabsorption in children is controversial. The need for correction for poor sample collection is disputed. We evaluated the relevance of methane/CO2 measurements for the diagnosis of paediatric carbohydrate malabsorption.

METHODS

A total of 132 breath tests (fructose: n = 54; lactose: n = 78) were performed in 91 children/adolescents with functional abdominal complaints. Breath samples were collected and analysed for hydrogen, methane, and CO2. Malabsorption was defined by a net increase over baseline of ≥20 parts per million (ppm) for hydrogen, ≥5 to ≥12 ppm for methane, and ≥10 to ≥15 ppm for hydrogen-plus-methane. The diagnosis was made before and after the use of a CO2-based correction factor (5.5% as the numerator). Hydrogen-based test results were compared with results obtained with other cut-off values.

RESULTS

Fifty-eight positive tests were obtained by hydrogen measurement (without CO2 correction). The addition of methane measurements did not significantly influence the test results (P > 0.05). Only under the use of extraordinary cut-offs (combined hydrogen-plus-methane smaller than ≥18 ppm) did the rate of malabsorbers increase significantly (P < 0.05). After CO2 correction, hydrogen ≥20 ppm was detected in 4 additional patients, but 1 patient lost the hydrogen-based diagnosis of malabsorption (Cohen kappa = 0.92).

CONCLUSIONS

Methane measurement did not significantly affect the detection rate of carbohydrate malabsorbers in children/adolescents with functional abdominal complaints when established cut-offs are used. The use of CO2 correction altered the diagnosis of malabsorption in a minority of patients but did not significantly alter overall test results.

Is There a Correlation Between Irritable Bowel Syndrome and Lactose Intolerance?

Irritable bowel syndrome (IBS) is a poorly understood gastrointestinal disorder that affects a significant percentage of the population and has a strong negative effect on the quality of life. The lack of known pathophysiologic mechanisms has made finding effective treatment strategies difficult. One of the common recommendations by clinicians is a trial of a lactose-free diet. We have wondered if there was sufficient evidence in the currently available literature to support such a recommendation. We have also looked into other possible relationships between malabsorption syndromes and IBS. All the articles used for this review have been found in the PubMed database. We have taken into consideration the possibility that there may be both genetic differences and differences in the gut microbiome between populations living in different geographic regions. Therefore, we have included articles from different geographic regions to increase the generalizability of the findings. While there is a plethora of evidence that IBS patients commonly report milk intolerance, we have not found any conclusive evidence to suggest an objective link between IBS and any known malabsorption syndromes, including lactose malabsorption. Furthermore, trials of lactase supplementation have not led to clinical benefit. We concluded that there was no evidence to support routinely recommending a lactose-free diet for patients diagnosed with IBS, but including hydrogen breath testing in routine workup of IBS is a reasonable clinical decision. Ultimately, we believe that more clinical trials and chemical studies of the feces are needed to determine the pathophysiology and explore possible dietary recommendations for patients with IBS.

Fecal Microbiota Alterations Associated With Diarrhea-Predominant Irritable Bowel Syndrome

Altered gut microbiota are assumed to be involved in the pathogenesis of irritable bowel syndrome (IBS). However, gut microbiota alterations reported in different studies are divergent and sometimes even contradictory. To better elucidate the relationship between altered gut microbiota and IBS, we characterized fecal microbiota of diarrhea-predominant IBS (IBS-D) patients and further explored the effect of rifaximin on gut microbiota using bacterial 16S rRNA gene-targeted pyrosequencing. In our study, IBS-D patients defined by Rome III criteria and age-and-gender matched healthy controls (HC) were enrolled to investigate the fecal microbiota alterations. These IBS-D patients were then treated with rifaximin for 2 weeks and followed up for 10 weeks. Fecal microbiota alterations, small intestine bacterial overgrowth (SIBO) and gastrointestinal (GI) symptoms of IBS-D patients were analyzed before and after treatment. Our results showed fecal microbiota richness but not diversity was decreased in IBS-D patients as compared to HC and there were alterations of fecal microbiota at different taxonomy levels. The abundant phyla Firmicutes was significantly decreased and Bacteroidetes was increased in IBS-D patients. Moreover, the alterations of predominant fermenting bacteria such as Bacteroidales and Clostridiales might be involved in the pathophysiology of IBS-D. In addition, rifaximin was effective in terms of SIBO eradication and even GI symptoms of IBS-D patients achieved at least 10-week improvement after treatment. Furthermore, rifaximin induced alterations of some special bacteria rather than affected the overall composition of microbiota in IBS-D patients. Meanwhile, a potential decrease in propanoate and butanoate metabolism was found in these IBS-D patients after rifaximin treatment. Taken together, there were alterations of gut microbiota in IBS-D patients as compared to HC. Rifaximin could relieve GI symptoms, modify gut microbiota in IBS-D patients and eradicate SIBO in those patients with SIBO, suggesting an additional therapeutic mechanism of rifaximin in the treatment of IBS-D. Our findings of compositional gut microbiota alterations in IBS-D and the effect of rifaximin on the gut microbiota implied that altered gut microbiota were associated with the pathogenesis of IBS.

Breath Hydrogen Testing in East and Southeast Asia

Breath hydrogen tests are popular, noninvasive tests for the assessment of carbohydrate fermentation in patients with irritable bowel syndrome (IBS) and functional dyspepsia (FD). There is limited information regarding the utility of breath hydrogen and methane tests in IBS and FD patients in East and Southeast Asia. This review aims to summarize current literature about common indications of breath testing in this region, the genesis of functional gastrointestinal symptoms by provocative breath testing and provide suggestions for correct use. The most common testing indication is the assessment of lactose intolerance, followed by small intestinal bacterial overgrowth (SIBO) and differentiation of intestinal gas profiles in research setting. Studies in this region not only documented a high prevalence of lactose malabsorption but a population, both healthy and IBS, that is highly symptomatic to typical lactose intakes. Breath hydrogen assessment of other fermentable carbohydrates (FODMAPs) are fairly uncommon, whereas methane breath testing is almost nonexistent. Cumulative hydrogen production following lactulose was also not excessive in IBS patients compared with controls. The evidence however, for the detection of SIBO suggests limited reliability in the use of lactulose or glucose breath testing alone and inconclusive data on its correlation with symptoms. Conversely, little has been carried out in FD. In conclusion, breath testing should be limited in the predicting patients with SIBO for directing clinical management but can be considered in the objective assessment of lactose malabsorption within a low FODMAP diet. Recommendations to improve the interpretation of breath testing in research were also provided.

Prevalence of lactose intolerance in patients with diarrhea-predominant irritable bowel syndrome: data from a tertiary center in southern China

BACKGROUND

Symptoms associated with lactose intolerance (LI) and diarrhea-predominant irritable bowel syndrome (IBS-D) are almost the same. These disease entities are difficult to differentiate clinically. In practice, differential diagnosis depends on self-reported patient milk intolerance. However, there is limited data on the prevalence of LI in China. The aim of this study was to investigate the prevalence of LI in IBS-D patients and asymptomatic healthy controls.

METHODS

Lactose malabsorption (LM) was diagnosed by a lactose hydrogen breath test (HBT) and was defined by peak breath H₂ excretion over the baseline level of ≥ 20 ppm. LI-related symptoms were monitored for 8 h following lactose administration. LI was defined in LM patients with positive symptoms during the observation time. Patients with IBS-D were additionally asked if they were intolerant to milk.

RESULTS

A total of 109 eligible IBS-D patients (Rome III criteria) and 50 healthy controls were enrolled in this study. Except for hydrogen non-producers, the prevalence of LM did not differ between IBS-D patients and the control group (85%, 82/96 vs 72%, 34/47; P = 0.061). There was, however, a higher LI prevalence in IBS patients than in healthy subjects (45%, 43/96 vs 17%, 8/47; P = 0.002). Sensitivity, specificity, and positive and negative predictive values of self-reported milk intolerance for detecting LI were 58, 58, 53, and 63%, respectively.

CONCLUSIONS

Prevalence of LI is significantly higher in IBS-D patients than in healthy subjects. Self-reported milk intolerance is a poor diagnostic predictor of LI.

Small Intestinal Bacterial Overgrowth in Patients with Refractory Functional Gastrointestinal Disorders

Background/Aims

Small intestinal bacterial overgrowth (SIBO) is considered to be involved in the pathogenesis of functional gastrointestinal disorders (FGID). However, the prevalence and clinical conditions of SIBO in patients with FGID remain to be fully elucidated. Here, we examined the frequency of SIBO in patients with refractory FGID.

Methods

We prospectively enrolled patients with refractory FGID based on Rome III criteria. A glucose hydrogen breath test (GHBT) was performed using a gas analyzer after an overnight fast, with breath hydrogen concentration measured at baseline and every 15 minutes after administration of glucose for a total of 3 hours. A peak hydrogen value ≥ 10 ppm above the basal value between 60 and 120 minutes after administration of glucose was diagnosed as SIBO.

Results

A total of 38 FGID patients, including 11 with functional dyspepsia (FD), 10 with irritable bowel syndrome (IBS), and 17 with overlapping with FD and IBS, were enrolled. Of those, 2 (5.3%) were diagnosed with SIBO (one patient diagnosed with FD; the other with overlapping FD and IBS). Their symptoms were clearly improved and breath hydrogen levels decreased to normal following levofloxacin administration for 7 days.

Conclusions

Two patients initially diagnosed with FD and IBS were also diagnosed with SIBO as assessed by GHBT. Although the frequency of SIBO is low among patients with FGID, it may be important to be aware of SIBO as differential diagnosis when examining patients with refractory gastrointestinal symptoms, especially bloating, as a part of routine clinical care.