Extended hydrogen breath test analysis for optimized diagnosis of SIBO-positive IBS patients

Small intestinal bacterial overgrowth (SIBO) is suggested in irritable bowel syndrome (IBS). Optimal hydrogen levels and time frame for diagnosing SIBO are still under discussion. Our primary aim was to consolidate a discriminating threshold for a positive lactulose hydrogen breath test (LHBT) in IBS. As a secondary aim, we optimized the diagnostic time frame for the small bowel. LHBT was performed on 503 subjects who met the inclusion criteria. After excluding non-hydrogen producers, the remaining 462 subjects were 92 healthy individuals and 370 IBS patients. Peak hydrogen levels were summarized as median values with interquartile range. At the 80-min orocecal cut-off, healthy subjects showed a peak hydrogen of 8(4–11) ppm compared with 10(4–29) ppm in the overall IBS group (p <0.0001). Using ≥20 ppm cut-off, sensitivity was 38% and specificity 77%. Peak hydrogen was highest in IBS-D (24(9-40) ppm; p <0.0001), intermediate in IBS-M (7(4-14) ppm), and lowest in IBS-C (7(4-10) ppm), showing sensitivities of 61%, 23%, and 10%, respectively, with specificity 77%.After antibiotics, IBS patients with low hydrogen were unchanged, whereas most with high hydrogen reduced their hydrogen levels (p <0.01). Using a cut-off level of ≥20 ppm during the first 80 minutes, LHBT can diagnose SIBO in people with IBS showing high breath hydrogen, as compared with those having low breath hydrogen. Hence, SIBO-positive patients can be separated from SIBO-negative IBS patients. To this end, a majority of SIBO-positive subjects respond to antibiotic treatment. • The lactulose hydrogen breath test can be used to diagnose SIBO-positive IBS patients. • A diagnostic cut-off level of 20 ppm hydrogen within 80 minutes indicates better diagnostic criteria for bacterial overgrowth. • A substantial proportion of IBS-D patients have high hydrogen emanating from the small intestine indicating small intestinal bacterial overgrowth.