[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.