Extending the Glucose Breath Test Beyond 60 Minutes Is Associated with a Negligible Increase in Diagnostic Yield

Abstract

Purpose: To determine the optimal duration of the glucose breath test (GBT) for evaluation of small intestinal bacterial overgrowth (SIBO). Methods: Five hundred and three patients (403 female; mean age 51 years) underwent a GBT for evaluation of SIBO. During the GBT, two breath samples were obtained at baseline and then at 30, 45, 60, 75 and 90 minutes following ingestion of 50g of glucose in 150 cc of water (isosmotic solution). The concentrations of hydrogen and methane from the breath samples were then recorded for each time point. The criteria for a positive GBT were: 1) a baseline hydrogen or methane concentration of >15 ppm, or 2) when baseline hydrogen or methane concentration was <10 ppm, a rise in concentration to a peak exceeding 20ppm, or 3) when baseline hydrogen or methane concentration was >10 ppm, a rise in peak hydrogen or methane concentration by >12 ppm. Results: One hundred and eighty-four (37%) patients had a positive GBT based on the criteria mentioned above, of which 125 (68%) were positive based on a rise in hydrogen level, 48 (26%) by a rise in methane level, and by a rise in both methane and hydrogen in 11 (6%). Eighty-six (47%) of these patients had a positive GBT based on methane or hydrogen levels at baseline, and 175 (95%) patients met the criteria for a positive GBT by the end of 60 minutes. Of the 328 patients who had a negative test based on the above criteria at 60 minutes, 9 (3%) had a positive test with continued monitoring of hydrogen breath samples up to 90 minutes. None of the patients had a positive test by virtue of a delayed increase (beyond 60 minutes) in methane concentration. Of those patients who had a delayed peak in hydrogen production, 5 had a history of chronic constipation, 2 had prior abdominal surgery in the form of ileocecal valve resection and Roux-en-Y gastric bypass, and 1 each had chronic pancreatitis and celiac sprue. Conclusion: 1) It is reasonable to stop collection of breath samples at 60 minutes during performance of GBT without significantly affecting the diagnostic accuracy of the test. 2) The 60 minute GBT could increase patient tolerability of the procedure and save on costs related to personnel and equipment. 3) It is plausible that the delayed rise of hydrogen concentration in the breath samples seen in 3% of patients could be explained by the role of colonic flora.