Diagnosis of Helicobacter pylori infection in children: Is the N-15 urine test more reliable than the C-13 breath test?

Background: The [C-13]urea breath test is a convenient method to estimate H elicobacter pylori colonization non-invasively. As an alternative method, t he [N-15]urea urine test has been established. It is hypothesized that the urine rest could be advantageous under some circumstances. The diagnostic v alue of the breath test might, for example, be jeopardized owing to fluctua ting C-13 isotope dilution by endogenous carbon dioxide. Methods: To compar e the reliability and practicability of the two tests, C-13 breath tests an d N-15 urine tests were performed simultaneously in three groups of patient s: A) 36 adults under standardized conditions, B) 67 children who were allo wed to move around during the test, and C) 18 children once without and onc e during standardized physical activity. Results: In the 36 adults there wa s a close correlation of the test results of the two methods (r = 0.88). In contrast, the correlation in the group of 67 children and infants was poor (r = 0.10). In the children with controlled activity the C-13 results fluc tuated, whereas the N-15 results remained unchanged. Conclusions: Owing to their identical biochemical basis the breath test and the urine test produc e the same diagnostic results in the same individuals if standardized pre-t est and test conditions are followed. However, factors such as physical act ivity during the test may provoke fluctuations with a tendency to decreasin g C-13 values. This could be due to additional isotope dilution by increase s in the endogenous production of C-12-carbon dioxide. We conclude that in very active children the N-15 urine test might be advantageous and more rel iable than the C-13 breath test.