The quick urease test , also known as the CLO test ( eng. Campylobacter-like organism test ), is a for the detection of Helicobacter pylori bacteria [1] . The basis of the test is the property of Helicobacter pylori to secrete the enzyme urease , which catalyzes the process of converting urea into ammonia and carbon dioxide .
Content
Process
The test is performed at the time of gastroscopy . Biopsy of the mucous is taken from the cavity of the stomach, placed in an environment containing urea and an indicator such as phenol red . Urease converts urea to ammonia, increases the pH of the medium, and changes the color of the yellow sample (negative) to red (positive). As a result of the reaction, the acid-base balance of the stomach ( pH of the medium) is shifted to the alkaline side, which is fixed by means of an indicator. The resulting biopsy is placed in a special cell with ready-made solutions. The speed of changing the color of the indicator from yellow to bright red depends on the urease activity, which, in turn, depends on the number of bacteria. The main purpose of the method is the primary diagnosis of the presence of Helicobacter pylori in patients. The sensitivity and specificity of this method is 90%.
Benefits
The method allows you to get a conclusion quickly - from several minutes to several hours. Its use does not imply the presence of special laboratory equipment or trained specialists and is performed directly by the endoscopist. Cheap for mass and individual use. Currently developed a large number of industrially manufactured urease tests.
There is evidence that H. pylori moves closer to the center of the stomach in patients undergoing treatment with proton pump inhibitors , and thus, samples of these patients should be obtained from the bottom and body of the stomach .
Disadvantages
With a small number of bacteria, discoloration in the urease test can occur after a few hours, and sometimes a false negative result is possible. In addition, the result may be positive in individuals whose stomach is inhabited by H.heilmanii , which has a close affinity with Helicobacter pylori . With the appearance of coccal forms of Helicobacter pylorii (for example, after unsuccessfully carried out therapy) that do not exhibit enzymatic urease activity, the result may be false-negative.
The specificity and sensitivity of this test is high compared with histopathological examination or . The test is often done as part of the diagnosis at the bedside in order to reduce the time and cost required for detecting Helicobacter in pathology testing.
Active gastrointestinal bleeding reduces the accuracy of the test [2] . .
Notes
- ↑ Medscape & eMedicine Log In .
- ↑ Laine LA, Nathwani RA, Naritoku W. Bleeding for Gynecology: Helicobacter pylori diagnostic testing: 1 month later (Dec 2005), pp. 853-859.