BackgroundWe evaluated the clinical utility of the13C-xylose breath test for the diagnosis of small bowel bacterial overgrowth in children.MethodsTo determine the optimal dose of13C-xylose, 29 healthy children, 3 to 12 years old, were randomly assigned to receive one of three doses of13C-xylose (10, 25, or 50 mg). After an overnight fast, the oral dose of13C-xylose was administered, and breath samples were collected every 30 minutes for 4 hours. Samples were analyzed for13CO2by gas chromatography with mass spectrometry. Using the 50 mg dose, we then performed nine breath tests with concurrent duodenal bacterial cultures in 6 children, 3 to 12 years old, with short-bowel syndrome (n = 2), immunodeficiency states (n = 1), and motility disorders (n = 3).ResultsExcretion of13CO2in breath peaked at 2.5 hours in all three control groups. The 50-mg dose produced the highest median peak and the smallest range of13CO2excretion in breath within each time period. The time of peak13CO2excretion in breath varied among the diseased children; however, the six patients with small-bowel bacterial overgrowth (2 × 105- 3.5 × 108gram negative rods) all had peak13CO2that exceeded the maximum breath13CO2level in breath of the control subjects at the corresponding time period (100% sensitivity). Of the three patients with negative cultures, two had negative breath test results and one had positive results (67% specificity). One subject had normalization of both duodenal culture and breath test results after antibiotic treatment of small-bowel bacterial overgrowth.ConclusionsOur preliminary results suggest that with a dose of 50 mg13C-xylose, breath test results reliably predict small-bowel bacterial overgrowth in susceptible children.