Using a cutoff of <10 ppm for breath hydrogen testing: a review of five years' experience.

To assess the clinical use of the breath hydrogen test in a large community hospital using a <10 ppm cutoff, we reviewed 222 tests performed over a 5-year period to evaluate patients for disaccharidase deficiency or bacterial overgrowth of the small intestine. Of these, the vast majority (195) were for lactose malabsorption, although fructose (17), sucrose (8) and lactulose (2) were also occasionally administered. One hundred eleven tests (50 percent) were positive, with an increase of at least 10 ppm hydrogen above the fasting level and a maximum value most commonly observed (42.3 percent of the time) at 3 hours post-administration. Only 34 patients (15.3 percent) had symptoms noted during the test, as compared with 185 (83.3 percent) who had experienced persistent intestinal problems prior to the test. Recent conditions which may have caused intestinal distress, such as transient disaccharidase deficiency, infections, surgery or other disorders like Crohn's disease, ulcerative colitis or food poisoning, were recorded in only 14 cases. Patterns consistent with bacterial overgrowth of the small intestine were observed in only 3 cases. Of 111 positives, 9 cases had increases between 10 and 20 ppm hydrogen and 7 showed the increase in the 3-hour sample, possibly reflecting a delayed transit through the intestine. Final diagnoses in 6 of these where information was available were for conditions other than malabsorption. We conclude that using a rise of 10 ppm to interpret a positive test does not contribute significantly to an increased frequency of false positives, but that patients with increases between 10 and 20 ppm probably are not lactase deficient.