C-13 urea breath test with nondispersive isotope-selective infrared spectrometry: Reproducibility and importance of the fasting status

Background. The C-13 urea breath test (C-13-UBT) is the most convenient met hod for diagnosing Helicobacter pylori infection noninvasively. Nondispersi ve isotope selective infrared spectrometry (NDIRS) is an inexpensive and ea sy alternative to mass spectrometry. The objective of this study was to eva luate: (1) the reproducibility of the C-13-UBT as performed by using the ND IRS method; (2) the repeatability of bags analysis and the impact of delaye d analysis; and (3) the need for fasting status for the C-13-UBT. Methods. The C-13-UBT was performed with 75 mg urea labeled with C-13, with breath samples collected at times 0 and 30 minutes. Results are expressed as delta over baseline (0/00). Fifty-three patients underwent two successiv e C-13-UBTs with an interval of 48 to 72 hours. The 106 collected bags were randomly reanalyzed immediately or 72 hours later. In 26 volunteer subject s, the C-13-UBT was performed both in a fasting condition and after a nonst andardized meal. The reproducibility was assessed by the method of Bland an d Altman. Results. The mean of difference between two successive tests was 0.14 0/00 (standard deviation, 0.90), and the coefficient of repeatability was 1.80 ( confidence interval, 95%). The difference between two successive analyses w as always less than 2.2% of the initial value. The coefficient of variation between two successive tests for the influence of a meal was 11.24. Conclusion. The C-13-UBT as performed by using NDIRS is reproducible, analy ses can be delayed up to 72 hours, and the test must be performed in fastin g conditions.