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

Gas-tly Interpretations: A Case-Based Approach to the Nuances of SIBO Breath Testing

PURPOSE OF REVIEW

Breath testing to diagnose intestinal microbial overgrowth (MO) is being increasingly utilized, in part due to direct-to-consumer testing modalities. However, the concept of breath testing in the diagnosis of MO is controversial due to numerous limitations regarding optimal substrate, diagnostic thresholds, and confounding variables. We provide seven real-world cases which comprehensively illustrate the principles and nuances of the interpretation of breath testing.

RECENT FINDINGS

We highlight recent studies which examine the optimal substrate for breath testing (glucose versus lactulose), the subtypes and clinical significance of breath test patterns including hydrogen, methane, and hydrogen-sulfide, elevated baseline gas levels, and confounders to breath test interpretation including transit time and diet. Reviewing the latest evidence, we provide recommendations for a personalized interpretation of breath tests utilizing unique patient factors. We conclude with an algorithm to assist clinicians in providing more accurate diagnoses.

Usefulness of a Digital Tool to Improve Methodology and Reporting of Breath Tests for Small Intestinal Bacterial Overgrowth

GOALS

We aimed to determine if the use of a web-based digital tool could improve methodology and reporting of breath tests (BT).

BACKGROUND

Although BT represent a noninvasive and low-cost tool for the diagnosis of small intestinal bacterial overgrowth (SIBO), lack of standardization and poor test performance have been described.

METHODS

We performed a retrospective analysis of a consecutive series of BT reports from 8 different gastroenterology units during the period April 2024 to July 2024. Data from the BT reports was extracted, masked, and uploaded in a digital tool that supports the entire breath test process and creates a report. Three experts in SIBO who were blinded for the test interpretation determined a diagnosis for each patient and delineated a total of 12 quality items that considered relevant to be included in a BT report. The main outcomes of the study were accuracy (ie, proportion of correct diagnoses) and quality of BT reports.

RESULTS

A total of 210 BT were analyzed; the type of substrate was informed in 187 (89.0%) BT and lactulose was used in most of the studies (162/187, 86.6%). Most tests measured only hydrogen (89.5%) and 38 (18.1%) extended the BT for <90 minutes. SIBO was diagnosed in 92 (43.8%) and 79 (37.6%) patients in the original BT report and the digital tool report, respectively. As compared with the diagnosis by the expert gastroenterologists and current guidelines, the original report was accurate in 182 (86.6%) patients and the digital tool report in 210 (100%) patients (P<0.0001). Regarding quality of reporting, the original BT report had a median of 5 (3 to 8) items included and the digital tool report described a median of 9 (7 to 11) items (P<0.0001).

CONCLUSIONS

Breath tests methodology and interpretation for the diagnosis of SIBO are heterogenous and do not comply with current guidelines. The use of a web-based digital tool specifically developed to assist the entire BT process appears to improve accuracy and quality of reports.

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.