Reassessing small intestinal bacterial overgrowth in irritable bowel syndrome: A comparative study of diagnostic guidelines and their clinical relevance

Loh, Audrey Joe Chii, Loo, Qing Yuan, Ng, Ai Kah, Khoo, Xin Hui, Siah, Kewin Tien-Ho, Majid, Hazreen Abdul, Mahadeva, Sanjiv and Chuah, Kee Huat (2026) Reassessing small intestinal bacterial overgrowth in irritable bowel syndrome: A comparative study of diagnostic guidelines and their clinical relevance. Journal of Gastroenterology and Hepatology. pp. 1-7. ISSN 1440-1746 (In Press)

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Abstract

Background/Aims: Hydrogen breath testing is a widely used, noninvasive method for diagnosing small intestinal bacterial overgrowth. However, diagnostic cut-offs vary across international guidelines. This study evaluated the diagnostic performance of differing criteria. Methods: We prospectively studied consecutive adults with irritable bowel syndrome who underwent glucose hydrogen breath testing. Small intestinal bacterial overgrowth was diagnosed using the Asia-Pacific consensus (rise in hydrogen ≥?12?ppm from baseline) and the North American consensus (rise ≥?20?ppm). Methane ≥?10?ppm was considered methane-positive in both. Results: Ninety subjects were included (median age 49?years; 53% female); 60% had diarrhea-predominant subtype. Small intestinal bacterial overgrowth was diagnosed in 44.4% using Asia-Pacific criteria and 37.8% using North American criteria. Hydrogen-positive cases were significantly associated with diarrhea-predominant subtype, while methane-positive cases correlated with constipation-predominant subtype. Severe irritable bowel syndrome symptoms (Symptom Severity Scale >?300) were more common in affected patients based on both Asia-Pacific (32.5% vs. 8.0%, p?=?0.003) and North American (29.4% vs. 12.5%, p?=?0.047) criteria. Only the Asia-Pacific criteria were significantly associated with higher symptom severity scores (median: 200 vs. 165, p?=?0.009), whereas this was not significant with the North American criteria (median: 200 vs. 170, p?=?0.087). Small intestinal bowel overgrowth was also linked to poorer quality of life and higher depression rates. Conclusion: The Asia-Pacific consensus diagnostic criteria improved detection and identified cases associated with more severe irritable bowel syndrome. These findings support using a lower hydrogen cut-off for breath testing, particularly in Asian populations.

Item Type:	Article
Keywords:	Disorder of gut–brain interaction, Functional gastrointestinal disorder, Gut dysbiosis, Pathophysiology
Schools:	School of Health and Rehabilitation Sciences
Depositing User:	Jessica Tovey
Date Deposited:	18 Jun 2026 08:54
Last Modified:	18 Jun 2026 08:54
URI:	https://hsu.repository.guildhe.ac.uk/id/eprint/659

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