Normalizing results of 13C-urea breath testing for CO2 production rates in children

Background: The C-13-urea breath test detects the presence of Helicobacter pylori from an enrichment of breath (CO2)-C-13, which, in turn, is critically dependent on the amount of dilution by endogenous CO2 production. The production of CO2 differs according to age (adults > children), sex (male > female) weight, and height. The cutoff value of 2.4 Delta% (delta over baseline, DOE) for the C-13-urea breath test, defined in adults, does not take into account actual CO, production. Therefore, this cutoff value (2.4 Delta%) may or may not be appropriate for children. The purpose of this study was to determine a cutoff value that would provide accurate results in pediatric patients, independent of their differences in anthropometric parameters. Methods: Estimates of CO2 production were combined with DOE values to calculate the host-dependent urea hydrolysis rate. Results: Calculated as urea hydrolysis rate, the cutoff range for adults was 10.4 to 10.9 mu g/min. Individual ranges were concentric (men, 9.6-10.9 mu g/min; women, 8.5-12.2 mu g/min). Results in studies of 312 children show that a urea hydrolysis rate of more than 10 mu g/min may also be appropriate to predict H. pylori infection. Conclusion: Calculating C-13-urea breath test values as urea hydrolysis rate removes the effect of individual anthropometric differences on test outcome and provides a single cutoff value for pediatric patients of all ages.