Urease is not present in mammalian cells, whereas Helicobacter pylori produces highly active urease. Since no other types of bacteria have been found in the human stomach, the detection of urease in the human stomach is evidence of H. pylori infection.

Positive subjects take 14C-labeled urea, and urease secreted by H. pylori will decompose the urea to produce 14C-labeled carbon dioxide and exhale from the lungs after circulation. The appropriate technology is used to collect the carbon dioxide gas exhaled by the subject and detect it on a highly sensitive instrument. If 14C-labeled carbon dioxide is detected, the subject can be judged as positive for Helicobacter pylori, otherwise it is negative.