A non-invasive diagnostic test used to detect active infection with Helicobacter Pylori bacteria in the stomach. It is based on measuring the ratio of radioactive carbon isotope (Carbon-13 or Carbon-14) in carbon dioxide in the patient's exhaled breath, after consuming a urea solution labeled with the radioactive isotope. If the bacteria are present, they break down the urea releasing radioactive carbon dioxide that is measured, indicating the presence of active infection.