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.

Pros and Cons of Breath Testing for Small Intestinal Bacterial Overgrowth and Intestinal Methanogen Overgrowth

Breath testing is the most widely utilized modality to diagnose small intestinal bacterial overgrowth (SIBO) and/or intestinal methanogen overgrowth (IMO). Although SIBO can be diagnosed with small bowel aspiration and breath testing, IMO can only be diagnosed with breath testing in clinical practice. Breath testing can tailor antibiotic therapy and predict response to treatment; however, the test is limited by its indirect method of measurement and concerns about the variability of orocecal transit time. Like any clinical test, breath testing has inherent strengths and limitations, and results must be interpreted with consideration of the clinical context and influencing factors. Recent studies have demonstrated the expanding clinical utility of breath testing in the diagnosis, management, and prediction of treatment response in SIBO and particularly in IMO along with the identification of distinct breath test patterns such as flat-line and high baseline hydrogen. This article reviews the strengths and limitations of breath testing in diagnosing SIBO and IMO as well as its expanding utility in clinical practice.

Serum Pepsinogen and Gastrin Levels: Reliable Markers to Predict Small Intestinal Bacterial Overgrowth

BACKGROUND

Serum pepsinogen, a useful indicator of gastric acidity, could reflect small intestinal bacterial overgrowth. The aim of this study is to evaluate the relationship between small intestinal bacterial overgrowth and profiles including pepsinogen or gastrin.

METHODS

We conducted a prospective study with 62 patients with a functional gastrointestinal disorder. All patients underwent glucose breath test for small intestinal bacterial overgrowth, immediately followed by upper endoscopy to survey gastric injury and Campylobacter-like organism test for Helicobacter pylori and serum laboratory tests including gastrin, pepsinogen I and II.

RESULTS

The positivity to small intestinal bacterial overgrowth was 17.7%. Significantly, low total hydrogen concentration during a glucose breath test, low prevalence for gastric injury, and high H. pylori positivity rate were shown in groups with pepsinogen I/II ratio ≤ 3.5 compared to those with pepsinogen I/II ratio > 3.5 or in groups with serum gastrin > 35.4 pg/mL comparing to those with serum ≤ 35.4 pg/mL, respectively. A high gastrin level was independently associated with H. pylori infection. A proportionally correlated tendency between pepsinogen I/II ratio and total hydrogen concentration was shown, whereas that of inverse proportion between H2 and gastrin was observed. Old age was solely independent predicting factor for small intestinal bacterial overgrowth (P = .03) in the multivariate analysis.

CONCLUSION

Old age was significantly related to the presence of small intestinal bacterial overgrowth in functional gastrointestinal disorder patients. Although pepsinogen and small intestinal bacterial overgrowth seem irrelevant, elevated gastrin level may cautiously indicate a decreased breath hydrogen concentration. Further studies should consider the function of intestinal motility and gastric acidity in patients with hydrogen-producing small intestinal bacterial overgrowth.

Does a glucose-based hydrogen and methane breath test detect bacterial overgrowth in the jejunum?

BACKGROUND

Direct diagnosis of small intestinal bacterial overgrowth (SIBO) requires the collection and culture of fluid from the jejunal lumen, with a finding of over 10⁵ viable bacteria per mL. More often, SIBO is diagnosed indirectly, using a non-invasive test of the exhaled hydrogen and methane generated by microbial fermentation when ingested glucose reaches the jejunum. Our objective was to determine how well this breath test detects chronic overgrowth of jejunal bacteria that is unrelated to gastrointestinal surgery.

METHODS

Eighteen patients reporting symptoms consistent with SIBO received a glucose breath test. On a later day, the jejunal lumen was sampled via aspiration during enteroscopy. Jejunal aspirates were cultured on aerobic and anaerobic media. DNA was extracted from the same samples and analyzed by quantitative pan-bacterial PCR amplification of 16S ribosomal rRNA genes, which provided a culture-independent bacterial cell count.

KEY RESULTS

Combined bacterial colony counts ranged from 5.7 x 10³ to 7.9 x 10⁶ CFU/mL. DNA-based yields ranged from 1.5 x 10⁵ to 3.1 x 10⁷ bacterial genomes per mL. Microbial viability ranged from 0.3% to near 100%. We found no significant correlation of glucose breath test results with either the number of bacterial colonies or with the DNA-based bacterial cell counts. Instead, higher signals in the hydrogen-methane breath test were significantly correlated with a lower viability of jejunal bacteria, at a P-value of .014.

CONCLUSIONS & INFERENCES

The glucose-based hydrogen and methane breath test is not sensitive to the overgrowth of jejunal bacteria. However, a positive breath test may indicate altered jejunal function and microbial dysbiosis.

Non-invasive diagnosis of type 2 diabetes in Helicobacter pylori infected patients using isotope-specific infrared absorption measurements

Helicobacter pylori causes several gastrointestinal diseases and may also contribute to the development of type 2 diabetes (T2D). Several studies suggest that there might be a potential link between H. pylori infection and T2D, but it still remains the subject of debate. Here, we first report the cumulative effect of H. pylori infection and T2D by exploiting the excretion kinetics of ¹³C/¹²C and ¹⁸O/¹⁶O isotope ratios of exhaled breath CO₂ in response to an oral dose of ¹³C-enriched glucose in individuals with T2D and non-diabetic controls (NDC) harbouring the H. pylori infection. Using a high-resolution integrated cavity output spectroscopy (ICOS) technique in the infrared region, we observed that the isotopic fractionations of ¹³C and ¹⁸O in breath CO₂ are distinctly altered in H. pylori infected T2D patients as well as in H. pylori infected NDC. Several optimal diagnostic cut-off points of ¹³C and ¹⁸O isotopes of breath CO₂ were also determined which exhibited the diagnostic sensitivity and specificity of ∼97 % and thus suggesting that breath ¹³C and ¹⁸O isotopes might be considered as potential biomarkers for the non-invasive assessment of the gastric pathogen prior to the onset of T2D. This may open a new diagnostic strategy for treating these common diseases in an alternative way.

Diagnosis and treatment of small intestinal bacterial overgrowth

A huge number of bacteria are hosted in the gastrointestinal tract, following a gradient increasing towards the colon. Gastric acid secretion and intestinal clearance provide the qualitative and quantitative partitioning of intestinal bacteria; small intestinal bacteria overgrowth (SIBO) occurs when these barrier mechanisms fail. Diagnosis of SIBO is challenging due to the low specificity of symptoms, the frequent association with other diseases of the gastrointestinal tract and the absence of optimal objective diagnostic tests. The therapeutic approach to SIBO is oriented towards resolving predisposing conditions, and is supported by antibiotic treatment to restore the normal small intestinal microflora and by modifications of dietary habits for symptomatic relief. In the near future, metagenomics and metabolomics will help to overcome the uncertainties of SIBO diagnosis and the pitfalls of therapeutic management, allowing the design of a personalized strategy based on the direct insight into the small intestinal microbial community.

Glucose breath test and Crohn's disease: Diagnosis of small intestinal bacterial overgrowth and evaluation of therapeutic response

OBJECTIVE

Small intestinal bacterial overgrowth (SIBO) is characterized by an abnormal proliferation of bacterial species in the small bowel. It has been shown that patients with Crohn's disease (CD) have a higher risk of SIBO development. The aim of the present study was to investigate SIBO prevalence in CD patients, possible clinical predictors of SIBO development and response to antibiotic therapy.

MATERIAL AND METHODS

Sixty-eight patients (42 male, 26 female; mean age 49.3 ± 12.8 years) with CD reporting abdominal complaints were prospectively evaluated for SIBO with H2/CH4 glucose breath test (GBT).

RESULTS

Of the 68 patients enrolled, 18 (26.5%) tested positive for SIBO. Patients with SIBO exhibited increased stool frequency and significant reduction of stool solidity (p = 0.014), were older than patients tested negative to GBT (54.3 ± 13.0 years vs. 47.5 ± 12.3 years, p = 0.049), reported a longer history of CD (21.2 ± 10.3 years vs. 15.7 ± 10.2 years, p = 0.031) and showed a significant higher frequency of prior surgery (p = 0.001), revealing an association of number of surgical procedures (OR = 2.8315, 95% CI = 1.1525-6.9569, p = 0.023) with SIBO. Breath test normalization occurred in 13/15 patients evaluated after antibiotic and probiotic therapy. Although vitamin B12 levels were lower in patients with SIBO (p = 0.045) and a significant improvement was found after treatment (p = 0.011), this could be due to the heterogeneity, regarding vitamin B12 treatment, in our cohort.

CONCLUSION

SIBO is a frequent but underestimated condition in CD, which often mimics acute flare, effectively identified with GBT and could be treated with a combined antibiotic and probiotic therapy.

Clinical significance of the glucose breath test in patients with inflammatory bowel disease

BACKGROUND AND AIM

Small intestinal bacterial overgrowth which has recently been diagnosed with the glucose breath test is characterized by excessive colonic bacteria in the small bowel, and results in gastrointestinal symptoms that mimic symptoms of inflammatory bowel disease. This study aimed to estimate the positivity of the glucose breath test and investigate its clinical role in inflammatory bowel disease.

METHODS

Patients aged > 18 years with inflammatory bowel disease were enrolled. All patients completed symptom questionnaires. Fecal calprotectin level was measured to evaluate the disease activity. Thirty historical healthy controls were used to determine normal glucose breath test values.

RESULTS

A total of 107 patients, 64 with ulcerative colitis and 43 with Crohn's disease, were included. Twenty-two patients (20.6%) were positive for the glucose breath test (30.2%, Crohn's disease; 14.1%, ulcerative colitis). Positive rate of the glucose breath test was significantly higher in patients with Crohn's disease than in healthy controls (30.2% vs 6.7%, P=0.014). Bloating, flatus, and satiety were higher in glucose breath test-positive patients than glucose breath test-negative patients (P=0.021, 0.014, and 0.049, respectively). The positivity was not correlated with the fecal calprotectin level.

CONCLUSIONS

The positive rate of the glucose breath test was higher in patients with inflammatory bowel disease, especially Crohn's disease than in healthy controls; gastrointestinal symptoms of patients with inflammatory bowel disease were correlated with this positivity. Glucose breath test can be used to manage intestinal symptoms of patients with inflammatory bowel disease.

Small intestinal bacterial overgrowth: duodenal aspiration vs glucose breath test

BACKGROUND

The 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.

METHODS

Patients with unexplained gas, bloating and diarrhea and negative endoscopy, imaging and blood tests were prospectively enrolled in two centers in USA. Randomly, within 1 week each patient underwent both duodenal aspiration/culture and GBT. The diagnostic yield of each test and relationship of symptoms, and effects of ethnicity, age, and gender on prevalence of SIBO were assessed and compared.

KEY RESULTS

Duodenal culture was positive in 62/139 (44.6%) subjects and GBT was positive in 38/139 (27.3%) subjects with an overall diagnostic agreement of 65.5%. The sensitivity, specificity, positive and negative predictive value of GBT was 42%, 84%, 68%, and 64%, respectively. Ethnicity or gender did not influence SIBO, but SIBO positive patients were older (p = 0.0018). Symptom patterns were similar except bloating was more prevalent in GBT positive and gas in culture positive subjects.

CONCLUSIONS & INFERENCES

Duodenal aspiration/culture identifies 45% of patients with suspected SIBO. GBT has lower sensitivity but good specificity for detection of SIBO. There were no ethnic or gender differences in the prevalence of SIBO, but patients with SIBO were older. Because GBT is non-invasive, it should be considered first in patients with suspected SIBO.