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 com bined C-13-lactose (CO2)-C-13/H-2 breath test, which was performed in 33 pa tients 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 r esults did not always occur in the same patients. In five of six patients w ith bath test results abnormal, lactase activity was low. In 13 of 15 patie nts 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 alo ne.