Small intestine bacterial overgrowth is frequent in cystic fibrosis: combined hydrogen and methane measurements are required for its detection.

Introduction: Hydrogen breath test (BT) is commonly used as a diagnostic tool for the detection of small intestine bacterial overgrowth (SIBO). It was reported that colonic methane production is far more frequent in cystic fibrosis (CF) patients than in other subjects. Therefore, measuring exclusively hydrogen in the diagnostic breath test for diagnosing SIBO might be of limited value. We aimed to assess the usefulness of combined measurement of hydrogen and methane expiration for the diagnosis of SIBO in CF.

Material And Methods: The study comprised 62 CF patients aged 5 to 18 years. Three-hundred-ninety subjects assessed due to gastrointestinal symptoms for the presence of SIBO served as a comparative group. In all subjects hydrogen/methane BT using glucose was performed. A positive BT was defined as fasting hydrogen > or = 20 ppm or fasting methane > or = 10 ppm or a rise of > or = 12 ppm hydrogen or > or = 6 ppm methane over baseline during the test.

Results: In 23 (37.1%) CF patients and in 52 (13.3%) subjects from the comparative group abnormal BT results were found. In seven (11.3%) CF patients and 29 (7.4%) of the other subjects studied methane measurement allowed diagnosis of SIBO.

Conclusions: Small intestine bacterial overgrowth is frequent in cystic fibrosis. For its detection in cystic fibrosis and other gastrointestinal patients, combined hydrogen and methane measurement instead of hydrogen breath test should be applied. Without the additional measurement of methane a significant percentage of SIBO will be missed.