Background: Although the accuracy of breath H2 testing to detect malabsorption of small (2 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.
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