Radioactive Carbon Incorporated in Urea for H. Pylori Test

The noninvasive test method used clinically for the diagnosis of Helicobacter pylori infection and post-eradication follow-up is the urea breath test (UBT). A probe for the bacteria has been developed by incorporating a radioactive isotope of carbon into the urea used for the test.

H. pylori produce an enzyme, urease, which catalyzes the hydrolysis of the urea molecule into ammonium and carbon dioxide. The urea contains one carbon atom that is replaced by the radioactive carbon isotope. The probe, developed by Stat Diagnostics Services (Mumbai, India), is called the Heliprobe instrument.

A Helicap (hard urea 14C) is ingested with 50 ml of water. When H. pylori are present in the stomach, urease metabolizes the C-urea releasing carbon dioxide containing the C-labeled atoms. The carbon dioxide passes through the mucosa into the blood stream and it is transported to the lungs where it is exhaled. The amount of CO2 produced in the stomach can be measured with the Heliprobe instrument.

If the patient is not infected, no metabolisation of urea will occur and therefore no CO2 is detected--the unmetabolised C urea will be excreted in the urine. If the Heliprobe system detects CO2, this is diagnostic evidence of an ongoing infection with H. pylori.

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