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There is a pressing need to develop a novel early-detection strategy for the precise evolution of small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome (IBS) patients. The current method based on a hydrogen breath test (HBT) for the detection of SIBO is highly controversial. HBT has many limitations and drawbacks. It often fails to indentify SIBO when IBS individuals have 'non-hydrogen-producing' colonic bacteria. Here, we show that hydrogen sulphide (H2S) in exhaled breath is distinctly altered for diarrhea-predominant IBS individuals with positive and negative SIBO by the activity of intestinal sulphate-reducing bacteria. Subsequently, by analyzing the excretion kinetics of breath H2S, we found a missing link between breath H2S and SIBO when HBT often fails to diagnose SIBO. Moreover, breath H2S can track the precise evolution of SIBO, even after the eradication of bacterial overgrowth. Our findings suggest that the changes in H2S in the bacterial environment may contribute to the pathogenesis of SIBO and the breath H2S as a potential biomarker for non-invasive, rapid and precise assessment of SIBO without the endoscopy-based microbial culture of jejunal aspirates, and thus may open new perspectives into the pathophysiology of SIBO in IBS subjects.

We report for the first time the excretion kinetics of the percentage dose of (13)C recovered/h ((13)C-PDR %/h) and cumulative PDR, i.e. c-PDR (%) to accomplish the highest diagnostic accuracy of the (13)C-urea breath test ((13)C-UBT) for the detection of Helicobacter pylori infection without any risk of diagnostic errors using an optical cavity-enhanced integrated cavity output spectroscopy (ICOS) method. An optimal diagnostic cut-off point for the presence of H. pylori infection was determined to be c-PDR (%) = 1.47 % at 60 min, using the receiver operating characteristic curve (ROC) analysis to overcome the "grey zone" containing false-positive and false-negative results of the (13)C-UBT. The present (13)C-UBT exhibited 100 % diagnostic sensitivity (true-positive rate) and 100 % specificity (true-negative rate) with an accuracy of 100 % compared with invasive endoscopy and biopsy tests. Our c-PDR (%) methodology also manifested both diagnostic positive and negative predictive values of 100 %, demonstrating excellent diagnostic accuracy. We also observed that the effect of endogenous CO2 production related to basal metabolic rates in individuals was statistically insignificant (p = 0.78) on the diagnostic accuracy. However, the presence of H. pylori infection was indicated by the profound effect of urea hydrolysis rate (UHR). Our findings suggest that the current c-PDR (%) is a valid and sufficiently robust novel approach for an accurate, specific, fast and noninvasive diagnosis of H. pylori infection, which could routinely be used for large-scale screening purposes and diagnostic assessment, i.e. for early detection and follow-up of patients.

The article discusses a study which investigated the time-dependent excretion kinetics of 18OO/16O isotope ratios of CO2 in exhalted breath samples for the detection of Helicobacter pylori infection in human stomach. Topics discussed include the use of an optical cavity-enhanced integrated cavity output spectroscopy (ICOS) method and the statistical distribution of 18OO/16O.