A mass spectrometric method for diagnosis of gastrointestinal infections by 13 C determination from respiratory CO2

The use of stable carbon isotopes in metabolic research on humans and large animals is expanding rapidly due to the increasing variety of labelled compounds, greater availability of analytical facilities, and absence of health risk from radiation.This study is focused on a new mass spectrometric technique to diagnose Helicobacter pylori (HP) infection of the gastric mucosa which results in ulcers and some forms of gastric cancer. The method is based on measuring 13 C-enrichment in exhaled air by isotope ratios mass spectrometry. In this breath test, 13 C-labelled urea is given orally to the patient. If HP is present, the 13 C-urea is decomposed rapidly by these bacteria to 13 CO2 which circulates to the lungs and is expelled in the breath where it can be detected. The protocol of the method is described and one example of the use of 13 C-urea is presented. The 13 C-enrichment in CO2 exhaled is measured by mass spectrometry with double collector and the results are expressed in relative delta (δ) per mil (o/oo) units. The instrumental precision was ± 0.12 o/oo. The δ 13 C was measured in both pre and post - dose breath samples collected from infected patient at 20, 40 and 60 min post-dose. The results showed 13 C increases of > 25 o/oo at 40 min, in good agreement with the data of literature. We concluded that these breath tests are ideally suited to diagnose HP infection as a nonradioactive, noninvasive and applicable to subjects of any population method. (authors)