Rapid urease test, also known as the CLO test (Campylobacter-like organism test), is a rapid test for diagnosis of Helicobacter pylori.[1] The basis of the test is the ability of H. pylori to secrete the urease enzyme, which catalyzes the conversion of urea to ammonia and bicarbonate.
The test is performed at the time of gastroscopy. A biopsy of mucosa is taken from the antrum of the stomach, and is placed into a medium containing urea and an indicator such as phenol red. The urease produced by H. pylori hydrolyzes urea to ammonia, which raises the pH of the medium, and changes the color of the specimen from yellow (NEGATIVE) to red (POSITIVE).
There is evidence to suggest that H. pylori moves proximal in the stomach in patients on therapy with proton pump inhibitors, and, as such, samples from the fundus and antrum should be taken in these patients.
The specificity and sensitivity of this test is high compared with histopathological examination or urea breath test. The test is often done as part of point-of-care diagnostics, to eliminate the time and expense required to detect H. pylori on pathology testing.