Rapid urease test (RUT test)

  • The sensitivity and specificity is more than 90%.
  • Obtaining tissue samples from the antrum and the fundus may increase the sensitivity of the test in these patients.
  • The CLO test is a qualitative RUT assay based on the detection of urease, produced by H. pylori.
  • The test system consists of a test well filled with a urea containing gel where the suspected tissue is inoculated and allowed to incubate. If H. pylori is present in the patient’s sample, urease will hydrolyze the urea in the gel leading to an accumulation of ammonium ions (NH4 +). This causes a rise in pH which is detected by a pH indicator in the test system changing from yellow to magenta. Other shades of red such as pink or orange are also considered positive. Yellow is considered a negative screen.
  • Gastric biopsy specimen should be taken preferably from an area that is not as eroded or denuded; H. pylori is present in smaller numbers in these areas than in otherwise normal looking tissue.
  • A CLO is reported as negative if there is no change in colour until the end of the 24 hour period.
  • CLO test may be falsely negative  in patients with recent gastrointestinal bleeding or with the use of PPIs, H2 antagonists, antibiotics, or bismuth-containing compounds as these agents suppress H. Pylori

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