Helicobacter pylori infection diagnostic tests
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Endoscopic Diagnostic Tests
Endoscopic diagnostic tests are biopsy-based diagnostic methods for H. pylori infection. This include:
- Site, number, and size of gastric biopsies
- Method of staining
- Level of experience of the examining pathologist
- Advantage of histology over other diagnostic studies is its ability to detect the pathological changes associated with H. pylori infection such as inflammation, atrophy, intestinal metaplasia, and malignancy.
- Multiple biopsies are required for accurate diagnosis as the prevalence and density of H. pylori varies throughout the stomach. Therefore a minimum of three biopsies is taken from different sites. They are:
- Greater curvature of the corpus
- Greater curvature of the antrum
- The sensitivity of histology is greatly affected by the use of medications such as bismuth, antibiotics, and PPI.
Rapid Urease Testing (RUT)
- The gastric biopsies obtained are placed into an agar gel or on a reaction strip containing urea, a buffer, and a pH-sensitive indicator.
- The urea is metabolized to ammonia and bicarbonate in the presence of H. pylori's urease leading to a pH increase in the microenvironment of the organism.
- A change in color of the pH sensitive indicator signifies the presence of the active infection.
- The sensitivity of the RUT decreases due to medications such as bismuth-containing compounds, antibiotics, or PPIs which reduce the density and/or urease activity of H. pylori.
- It is recommended that biopsies are taken from two sites due to the patchy distribution of H. pylori infection after antibiotics use. The sites include:
- The body at the gastric angularis
- Greater curvature of the antrum
- PPIs are withheld for 1-2 wk before the performance of RUT as they reduce the sensitivity of the test.
- Culture is not as sensitive as RUT or histology.
- Highly specific method for identifying active H. pylori infection.
- It is also used to determine antibiotic sensitivities and resistance.
Polymerase Chain Reaction (PCR)
- PCR is highly specific and more sensitive than other biopsy-based diagnostic techniques.
- It is also used to identify mutations associated with antimicrobial resistance.
- This method is not standardized across laboratories
|*2. Rapid urease testing||
|*4. Polymerase chain reaction||
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