A: Correct. The basis of this study is that the Helicobacter pylori bacteria present in the stomach in patients with this infection contain the enzyme urease necessary for the breakdown of urea. This metabolism of C-14 labeled urea results in the formation of C-14 labeled CO2 gas which is then detected using a liquid scintillation counter. In the absence of the bacterial infection the cells of the gastric mucosa which lack the enzyme urease (like all mammalian tissue) are unable to break down the urea and thus no C-14 labeled CO2 gas is formed resulting in a negative study.B: Incorrect. The study has nothing to do with the presence or absence of gastric acid. Only the pres-ence of the enzyme urease found in the Helicobacter pylori organisms but not in the gastric cells can break down the C-14 urea to form C-14 labeled CO2 gas.C: Incorrect. The physiology of the study is as described above. In no way is the formation of glucose or other aspects of carbohydrate metabolism involved.D: Incorrect. Again the metabolism of C-14 labeled urea by bacterial urease is the basis of the study. Renal excretion is not involved and no urine collections are performed. The study is performed by having the patient ingest the radiopharmaceutical followed by collection of two breath samples which are analyzed in a liquid scintillation counter for the presence of C-14 labeled CO2 gas.
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