The 13 C-urea breath test ( 13 C-UBT) is widely used as a non-invasive global method to detect Helicobacter pylori (HP) infection. The aim of the study was to assess the clinical reproducibility of the test. Twenty-seven healthy volunteers entered the study. 13 C-UBT (100 mg 13 C-urea, citric acid as a test drink) was performed in all subjects twice within three days. Duplicate breath samples were collected in 5-minute intervals and were analysed twice by isotope ratio mass spectrometry. Six persons were positive in both tests, 21 subjects were negative when the cut-off 3.5 was used (reproducibility of the positive or negative result 100%). Mean inter-test range of measure- ment in HP-positive persons was 14.4%. 13 C-UBT is an accurate non-invasive test to diagnose HP, the clinical reproducibility of the test is high, the reproducibility of correct results is 100%.

        Key words: Helicobacter pylori, non-invasive diagnostic test, 13 C-urea breath test, isotope ratio mass spectro- metry.