Comparison of isotope ratio mass spectrometry and nondispersive isotope-selective infrared spectroscopy for 13C-urea breath test.

OBJECTIVES: The 13C-urea breath test (UBT) is a sensitive and noninvasive method to diagnose Helicobacter pylori infection, but mass spectrometry (IRMS) is very expensive. The aims of this study were to compare the new low-priced infrared spectroscopy with IRMS in detecting the infection and to assess the influence of feeding on test accuracy.
METHODS: One hundred thirty-four patients with dyspeptic symptoms were recruited. Of these, 74 were infected and 60 uninfected on the basis of both CLO-test and histology. A subgroup of 37 patients (22 H. pylori-positive and 15 H. pylori-negative) was studied under fasting and nonfasting conditions on two different days. Duplicate breath samples were analyzed with two IRMS systems (Breath Mat and ABCA) and an infrared spectrometer (IRIS) before, 15 min, and 30 min after ingestion of 75 mg 13C-urea with citric acid. In 37 patients the test was repeated the day after the fasted one and was performed 60 min after a meal of 800 Kcal.
RESULTS: There was a close correlation between IRIS and Breath Mat (r = 0.969 at 15 min and r = 0.977 at 30 min; p < 0.0001), IRIS and ABCA (r = 0.963 at 15 min and r = 0.985 at 30 min; p < 0.0001), and Breath Mat and ABCA (r = 0.987 at 15 min and r = 0.981 at 30 min; p = 0.0001). The sensitivity ranged from 97-100% at both times with all devices, although the specificity was slightly inferior with the infrared system than with the two IRMS machines (95% vs 98-100% at 30 min), but the difference was not significant (p = NS). Food intake produced three false negative results in all three machines and a systematic shift to lower 6 values in infected patients.
CONCLUSIONS: Infrared spectroscopy can be considered a valid alternative to mass spectroscopy for the diagnosis of H. pylori infection. Fasting is required to guarantee an accurate test.