Application of isotope-selective non-dispersive infrared spectrometry for the evaluation of the C-13-urea breath test: comparison with three concordant methods

The aim of this work was to compare the performance of isotope-selective no n-dispersive infrared spectrometry (IRIS) for the C-13-urea breath test wit h the combination of the C-14-urea breath test (C-14-UBT), urease test and histologic examination for the diagnosis of H. pylori (HP) infection. Fifty -three duodenal ulcer patients were studied. All patients were submitted to gastroscopy to detect HP by the urease test, histologic examination and C- 14-UBT. To be included in the study the results of the 3 tests had to be co ncordant. Within one month after admission to the study the patients were s ubmitted to IRIS with breath samples collected before and 30 min after the ingestion of 75 mg C-13- urea dissolved in 200 mi of orange juice. The samp les were mailed and analyzed 11.5 (4-21) days after collection. Data were a nalyzed statistically by the chi-square and Mann-Whitney test and by the Sp earman correlation coefficient. Twenty-six patients were HP positive and 27 negative. There was 100% agreement between the IRIS results and the HP sta tus determined by the other three methods. Using a cutoff value of delta-ov er-baseline (DOB) above 4.0 the IRIS showed a mean value of 19.38 (minimum = 4.2, maximum = 41.3, SD = 10.9) for HP-positive patients and a mean Value of 0.88 (minimum = 0.10, maximum = 2.5, SD = 0.71) for negative patients. Using a cutoff value corresponding to 0.800% CO2/weight (kg), the C-14-UBT showed a mean Value of 2.78 (minimum = 0.89, maximum = 5.22, SD = 1.18) in HP-positive patients. HP-negative patients showed a mean value of 0.37 (min imum = 0.13, maximum = 0.77, SD = 0.17). IRIS is a low cost, easy to manage , highly sensitive and specific test for H. pylori detection. Storing and m ailing the samples did not interfere with the performance of the test.