VALIDATION OF [C-13]UREA BREATH TEST FOR HELICOBACTER-PYLORI USING A SIMPLE GAS-CHROMATOGRAPH MASS-SELECTIVE DETECTOR

Objective Isotope ratio mass spectrometry (IRMS) is the accepted metho d 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 Hel icobactor pylori, The IRMS instrument, an expensive and highly special ized 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 th e selected ion monitoring mode. The reference (CO2)-C-13:(CO2)-C-12 ra tio was from NBS19 obtained from the US National Institute of Standard s and Technology. (CO2)-C-13:(CO2)-C-12 ratios of the breath samples w ere determined. Excess delta per thousand (per mil, delta parts per th ousand) 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 histolog y determined blind to each other were compared. Results The coefficien t 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 s pecificity (95.8%) of the GC-MSD C-13-UBT were comparable to those of other methods of H. pylori diagnosis. Conclusion A gas chromatograph c oupled to a mass selective detector that is available in many analytic al and biomedical laboratories can be used for the C-13-UBT. This meth od will increase the availability and reduce the cost of this non-inva sive, non-radioactive diagnostic test. (C) 1998 Lippincott-Raven Publi shers.