Validation of [13C]urea breath test for Helicobacter pylori using a simple gas chromatograph mass selective detector

Objective Isotope ratio mass spectrometry (IRMS) is the accepted method for accurately measuring the (CO2)-C-13:(CO2)-C-12 ratio in the non-invasive and non-radioactive [C-13]urea breath test (C-13-UBT) for Helicobactor pylori, The IRMS instrument, an expensive and highly specialized analyser, is rarely available. The objective of this project was to modify and validate the use of a simple bench-top gas chromatograph-mass selective detector (GC-MSD) for 13C-UBT. Methods Breath samples from 71 patients were taken at baseline and 30 min after ingestion of 100 mg [C-13]urea. The breath samples were analysed using GC-MSD in the selected ion monitoring mode. The reference (CO2)-C-13:(CO2)-C-12 ratio was from NBS19 obtained from the US National Institute of Standards and Technology. (CO2)-C-13:(CO2)-C-12 ratios of the breath samples were determined. Excess delta per thousand (per mil, delta parts per thousand) of the 30 min sample over the baseline (Delta delta parts per thousand) of greater than or equal to 6 Delta delta parts per thousand was considered H. pylori positive. Results from C-13-UBT and histology determined blind to each other were compared. Results The coefficient of variation of the reference (CO2)-C-13:(CO2)-C-12 ratio was 0.06%. Using histology as the 'gold standard', the sensitivity (97.9%) and specificity (95.8%) of the GC-MSD C-13-UBT were comparable to those of other methods of H. pylori diagnosis. Conclusion A gas chromatograph coupled to a mass selective detector that is available in many analytical and biomedical laboratories can be used for the C-13-UBT. This method will increase the availability and reduce the cost of this non-invasive, non-radioactive diagnostic test. (C) 1998 Lippincott-Raven Publishers.