Accuracy of breath tests using low doses of 13C-urea to diagnose Helicobacter pylori infection:: a randomised controlled trial

Background: The C-13-urea breath test (UBT) for detecting Helicobacter pylori infection is a non-invasive method based on the organism's urease activity. Since its first description, the method has been extensively modified. However, only the dose of C-13-urea and the measurement equipment are directly related to the cost of the test. Aims: (1) To assess the diagnostic accuracy before eradication therapy of three UBTs using 25, 15, and 10 mg of C-13-urea, respectively; and (2) to determine diagnostic performance in the post-eradication setting showing the highest values for sensitivity and specificity with the lowest dose of C-13-urea. Methods: Three hundred consecutive patients were randomised to be tested with one of the three UBTs. All patients underwent upper endoscopy with biopsies. A total of 222 more patients were enrolled to evaluate the second aim. Infected patients were offered treatment and asked to return 4-6 weeks after the end of therapy to perform endoscopic follow up and to carry out C-13-UBT. Results: In the pretreatment setting, C-13-UBT 25 mg had a sensitivity of 100% (95% confidence interval (CI) 91.8-100) and a specificity of 100% (95% CI 93.7-100); C-13-UBT 15 mg had a sensitivity of 96.1% (95% CI 86.8-98.9) and a specificity of 100% (95% CI 92.6-100); and C-13-UBT 10 mg had a sensitivity of 89.1% (95% CI 77-95.3) and a specificity of 100% (95% CI 93.3-100). As the test with the best performance and the lowest dose of C-13-urea was C-13-UBT 15 mg, it was evaluated after treatment, reporting a sensitivity of 100% (95% CI 79.6-100) and a specificity of 98.9% (95% CI 94.3-99.8). Discussion: UBTs using 25 and 15 mg of C-13-urea were both accurate in the diagnosis of H pylori infection in untreated patients. C-13-UBT 15 mg was also accurate for follow up of patients after treatment.