Diagnosing Small Intestinal Bacterial Overgrowth

I have read with great interest the review article “Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management” by Rao and Bhagatwala (1). This article presents a comprehensive review on various diagnostic and clinical aspects as well as treatment modalities associated with small intestinal bacterial overgrowth (SIBO). Of note, the authors also report on their procedural experience using a 6F Liguory catheter with multiple side holes at its tip for the collection of small bowel aspirate. In clinical practice, the diagnosis of SIBO remains challenging because there is no widely accepted diagnostic test (2). On the one hand, the utility of aerobic and anaerobic culture in the diagnosis of SIBO is not fully known (2), on the other hand, although considered safe and noninvasive, hydrogen (H2)/methane (CH4) breath testing still lacks standardization across medical diagnostic laboratories worldwide (1,3). With this respect, the North American Consensus on hydrogen and methane-based breath testing in gastrointestinal disorders recommends the administration of 75 g of glucose or 10 g of lactulose mixed with or followed by 1 cup of water (3). A breath test is positive for SIBO when there is a rise in H2 concentrations of ≥20 ppm from baseline by 90 minutes. Furthermore, a breath test is considered positive when there is a CH4 level of ≥10 ppm at any time during the breath test (3). In their paper (1), Rao and Bhagatwala state that an increase in H2 concentrations of ≥20 ppm from baseline within 90 minutes and an increase from baseline in CH4 concentrations of ≥10 ppm within 2 hours are considered diagnostic of SIBO, also referencing to the diagnostic criteria defined by the North American Consensus (3). In addition, within Table 2 describing various diagnostic tests for SIBO, the authors mention a rise in CH4 levels ≥10 ppm from or above baseline as a sufficient criterion when breath testing is performed with glucose or fructose, again with reference to the diagnostic criteria defined by the North American Consensus (3). Given the fact that a CH4 fasting (baseline) level of ≥10 ppm can predict positivity in up to 86.4% of patients on lactulose and/or glucose breath testing (4,5), it is deemed necessary to clearly delimit CH4 positivity to either a single concentration measurement (i.e., ≥10 ppm), may it be the baseline level or not, or a change in concentration determination based on 2 measurements (i.e., ∆ ≥10 ppm between a measurement after the ingestion of sugar and the baseline level). CONFLICTS OF INTEREST Guarantor of the article: Gernot Kriegshäuser, MD, PhD. Specific author contributions: Sole author. Financial support: None to report. Potential competing interests: None to report.