Refined Lactulose Hydrogen Breath Test (LHBT)

The refined Lactulose Hydrogen Breath Test (LHBT) is a noninvasive and efficient diagnostic tool used to detect Small Intestinal Bacterial Overgrowth (SIBO) and classify Irritable Bowel Syndrome (IBS) patients based on their hydrogen production levels. This study aimed to enhance the accuracy of LHBT by optimizing its diagnostic parameters and improving patient differentiation.

Key improvements included defining the optimal hydrogen cutoff level at 20 ppm, which balanced sensitivity (77%) and specificity (88%) for detecting SIBO. The orocecal transit time (OCTT) was verified using scintigraphy, establishing an 80-minute diagnostic window. This refinement minimized false positives caused by rapid intestinal transit and improved precision compared to previous 90-minute guidelines.

The study analyzed 206 participants, including healthy controls, SIBO-predisposed individuals, and IBS patients. IBS patients were subdivided into high-hydrogen IBS (above 20 ppm) and low-hydrogen IBS (below 20 ppm). High-hydrogen IBS patients showed bacterial overgrowth patterns similar to confirmed SIBO cases, particularly in diarrhea-predominant IBS (IBS-D), which had significantly higher hydrogen levels compared to constipation-predominant IBS (IBS-C).

The effectiveness of antibiotic therapy was validated, as high-hydrogen IBS patients experienced reduced hydrogen levels and symptom relief after treatment, confirming SIBO’s role in their symptoms. Statistical analyses, including ROC curve and AUC evaluations, demonstrated the reliability of the 20 ppm cutoff.

This refined LHBT method provides a robust framework for diagnosing SIBO and stratifying IBS patients. It offers clinicians a precise tool to identify SIBO-related IBS cases and guide targeted treatment strategies, such as antibiotics, for symptom management.