The urease test is designed to detect Helicobacter pylori in gastric or duodenal biopsy samples. The test is based on the physiological ability of Helicobacter pylori to secrete large amounts of urease. This enzyme breaks down the urea in the test and produces ammonia, which causes the colour of the test disc to change from yellow to pink, and then to reddish-pink (buccal colour) and violet.