Clinically feasible stable isotope technique at a reasonable price: analysis of 13CO2/12CO2-abundance in breath samples with a new isotope selective-nondispersive infrared spectrometer.

Up to now, stable isotope analysis of carbon dioxide in breath samples is carried out with sensitive but very expensive and complex isotope ratio mass spectrometry (IRMS). Aiming at a more widespread application of breath tests in gastroenterological diagnostic routine, we tested a newly developed isotope selective non-dispersive infrared spectrometer (NDIRS) in comparison to IRMS. 13C-urea breath tests were performed in 63 patients as the routine screening method for Helicobacter pylori infection. Breath samples at baseline and (15) 30 min after administration of the test solution containing 13C-urea were analysed both by NDIRS and conventional IRMS. The correlation between the delta values of both devices was linear and in good agreement (r = 0.96; p < 0.0001; Y = 1.01 X -0.94). Comparing the delta over baseline-values, the correlation was Y = 1.11 X -0.36 (r = 0.98; p < 0.0001). Referring to the diagnosis of Helicobacter pylori infection with IRMS we calculated a sensitivity of 95.0% and an unchanged specificity (100%) for NDIR analysis. In conclusion, NDIRS appears a promising, easy to operate, and low cost potential alternative to conventional IRMS thus encouraging further detailed investigation and more widespread application of the noninvasive stable isotope technique in breath tests for gastrointestinal function testing.