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.