13C-urea breath test for the detection of H. pylori infection in children: determination of the cut-off point by a graphic method not depending on the gold standard

ABSTRACT

Background: validation of 13C-urea breath test (UBT) in children has been troublesome, The aim of the study was to determine the cut-off value of UBT in childhood using a graphic method and not depending on comparison to the gold standard, Methods: Open, prospective study. The authors studied 84 healthy children [44 (52por cento) female, mean age 6 years (min. 8 mo, max. 12y.0)]. UBT (IRIS, Wagner Analysen-Technik, Bremen, Germany) was perfomed using a dose of 50 mg of 13-C-urea for children up to seven years of age and of 75 mg for children older than seven. breath samples were collected before and 25 (T15), 30(T30) and 45 (T45) min after ingestion of the isotope. Mathematical analysis (log transformation for condensation of the results, Gaussian distribution and Ryan-Joiner normality test) and visual graphic analysis were performed for the determination of the cut-off point Results: According to the graphical and mathematical analysis, the cut-off value was determined to be 40/00 DOB (delta over baseline) at T30 and located at more than 3 SD from the mean for the low urease activity group and at 2.94 SD from the mean for the high urease activity group. 22 children (26por cento) were consideres positiv and 62 (74por cento) negative. Conclusion: This siple low-cost methodology can establish a reliable cut-off point for children, with high sensitivity and specificity. The procedure does not require the use of a comparative method or of a gold standard. Moreover, this practical tool can also be used by the laboratories to monitor UBT perfomance over time