Detection of malabsorption of low doses of carbohydrate: Accuracy of various breath H₂ criteria

Background: Although the accuracy of breath H₂ testing to detect malabsorption of small (<50 g) doses of carbohydrate has never been evaluated, studies suggest that its accuracy is limited by a high prevalence of "H₂ nonproducers." The aim of this study was to determine the accuracy of H₂ breath testing in the detection of malabsorption of 10 g of carbohydrate. Methods: In 55 healthy subjects, we determined the ability of breath H₂ measurements to distinguish between the ingestion of 10 g of a nonabsorbable carbohydrate (lactulose) and two control meals, a nonabsorbable electrolyte solution or glucose (10 g). Results: The conventional criterion of a 20 ppm increase in breath H₂ had 100% specificity but failed to identify lactulose malabsorption in 47% and 24% of subjects at 4 and 8 hours of testing. In contrast, a breath H₂ of >6 ppm at 5 or 6 hours had near perfect specificity and sensitivity. A sum of breath H₂ at 5, 6, and 7 hours of >15 ppm yielded perfect separation between lactulose and control solutions. Conclusions: True "H₂ nonproducers" are extremely rare. Using appropriate criteria, breath H₂ testing provides a very accurate means of identifying malabsorption of low doses of carbohydrate.