13C-urea breath test threshold calculation and evaluation for the detection of Helicobacter pylori infection in children.

Background: The 13C-urea breath test (UBT) is performed in adults and children with epigastric pain for non-invasively diagnosing a suspected H. pylori infection. Criteria for UBT interpretation have not been generally agreed on and test reliability has not been established in children of different ages. This study aimed at identifying reliable UBT thresholds in children by using 251 UBTs in conjunction with reference histology and by analyzing 1232 UBTs.

Methods: At baseline and 30 and 60 minutes after the administration of 75 mg 13C-urea to children and adolescents (0.25 to 18 years of age), the differences (Delta) of 13CO2/12CO2 ratio in exhaled air (delta) were determined by mass spectrometry. UBT Deltadelta value thresholds were calculated in random subgroups and evaluated in complementary subgroups using logistic regressions on reference histology or bimodal distribution analyses of Deltadelta values from UBTs alone.

Results: Deltadelta values were higher (median, 15.4 per thousand) in positive (133/251, 53 %) than in negative histology (2.4 per thousand). At 30 minutes, the calculated cut-off was 5.3 per thousand (mean regression determination R2 = 0.91), and sensitivity (0.95), specificity (0.97), positive (0.97) and negative predictive values (0.95) were higher than at 60 minutes (threshold 6.8 per thousand, R2 = 0.85). Similar thresholds resulted from UBTs analysis (5.8 per thousand and 6.2 per thousand) when sensitivity and specificity were maximized (concordance probabilities, 0.99 and 0.99). There was no systematic age effect.

Conclusions: In children, 13C UBT cut-offs were obtained and specially validated, entailing high accuracy of non-invasively testing for gastric H. pylori infection.