[The diagnostic value of hydrogen sulfide breath test for small intestinal bacterial overgrowth]

Objective: To evaluate the diagnostic value of hydrogen sulfide breath test(SBT) for small intestinal bacterial overgrowth (SIBO). Methods: College students were enrolled to complete gastrointestinal symptom scale, food frequency questionnaire, lactulose hydrogen- methane breath test (LHMBT) and SBT. Based on the correlation between hydrogen sulfide(H₂S) and hydrogen or methane gas,the receiver operating characteristic (ROC) curve of H₂S was drawn and diagnostic criteria of SBT was defined. Results: A total of 300 subjects including 84 males and 216 females with age 17-32 (21.6±2.4) years were enrolled from April 2019 to December 2019 and divided into two groups.Two hundred and three patients reported SIBO discomforts with 99 (48.8%) LHMBT positive, while 38 (39.2%) were LHMBT positive in 97 health controls. Rise of H₂S at 90 min was positively related with that of hydrogen (r=0.516, P<0.01), and H₂S levels at 90 min were positively correlated with methane (r=0.632, P<0.01). A rise in H₂S of ≥25.0 ppb or H₂S levels ≥62.5 ppb at 90 min during lactulose breath test was considered positive for SIBO, that sensitivity, specificity and accuracy were 66.4%,79.1% and 73.3% respectively. H₂S levels were significantly related to the amount of Vitamin B₁₂ intake (P=0.011). H₂S-positive subjects exhibited a constipation-predominant pattern. Conclusion: SBT is consistent with LHMBT, especially in constipation-predominant patients, which may provide a reference to the diagnosis of SIBO.