Background: In an attempt to identify the minimum criteria for scoring the 13C-urea breath test, we examined test results from 96 healthy subjects, 270 duodenal ulcer patients undergoing treatment to eradicate Helicobacter pylori, and 1000 consecutive breath tests analyzed in our laboratory.
Methods: The 13CO2/12CO2 isotope ratio in a baseline sample was compared with that of samples collected at 20, 30, 40, and 50 min post-dosing. A positive test was defined as an average increase in the ratio of 6/1000 over baseline. Values for a two-sample analysis (baseline and one other) and for a single-sample analysis were extracted from the data and compared with the original analysis outcome.
Results: Test results were negative for 186 patients and positive for 84. The two-sample method had high specificity (94-99/1000), sensitivity (95-99/1000), and positive predictive value (88-97/1000). False-positive results occurred most often with samples collected at 20 min and least often with the sample at 40 min (11 and 1, respectively). Analyses based on a single sample collected beyond 20 min, in which samples with an isotope ratio > or = -15/1000 versus the standard were defined as positive, gave comparable specificity (98-99/1000), slightly reduced sensitivity (92-94%), and positive predictive value (96-99%). The analyses of 1000 consecutive breath tests yielded approximately 1% false-positive and false-negative results by the two-sample method; the single-sample method yielded a 2% false-positive and false-negative result.
Conclusion: The 13C-urea breath test can determine H. pylori infective status from a single breath sample collected at least 30 min post-dose in which the absolute 13C abundance is > or = -15/1000 versus the standard.