Non-invasive detection of low-intestinal lactase activity in children by use of a combined (CO2)-C-13/H-2 breath test

Background: The aim of the study was to diagnose hypolactasia with a higher accuracy than with the traditional H-2 breath test. Methods: We used a combined C-13-lactose (CO2)-C-13/H-2 breath test, which was performed in 33 patients in whom lactase activity was measured. Results: Lactase activity was reduced in 13 cases. The sensitivity and specificity of the H-2 test were 54 % and 90 %; those of the (CO2)-C-13 test 69 % and 70 %. False-negative results did not always occur in the same patients. In five of six patients with bath test results abnormal, lactase activity was low. In 13 of 15 patients with both test results normal, lactase activity was normal. In 6 of 12 cases with only 1 test abnormal, lactase activity was low. Conclusion: The combined H-2/(CO2)-C-13 breath test (sensitivity, 85 %; specificity, 65 %) is more adequate for diagnosis of hypolactasia than the H-2 breath test alone.