Helicobacter pylori infection diagnostic tests: Difference between revisions
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* In patients who have not been on a PPI within 1-2 wk or an | * In patients who have not been on a PPI within 1-2 wk or an antibiotic or bismuth within 4 wk of endoscopy, the rapid urease test (RUT) provides an accurate, inexpensive means of identifying H.pylori. | ||
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* Though culture or polymerase chain reaction (PCR) are the primary means by which antibiotic | * Though culture or polymerase chain reaction (PCR) are the primary means by which antibiotic sensitivities can be determined, neither is widely available for clinical use in the United States and therefore, cannot be routinely recommended. | ||
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Endoscopic diagnostic tests are biopsy-based diagnostic methods for H.pylori infection. | Endoscopic diagnostic tests are biopsy-based diagnostic methods for H.pylori infection. This include: | ||
*Histology | *Histology | ||
*Rapid urease testing | *Rapid urease testing | ||
Line 29: | Line 29: | ||
:*Method of staining | :*Method of staining | ||
:*Level of experience of the examining pathologist | :*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. | *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 | *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: | ||
:*Angularis | :*Angularis | ||
:*Greater curvature of the corpus | :*Greater curvature of the corpus | ||
:*Greater curvature of the antrum | :*Greater curvature of the antrum | ||
*The sensitivity of histology is greatly | *The sensitivity of histology is greatly affected by the use of medications such as bismuth, antibiotics, and PPI. | ||
===Rapid Urease Testing (RUT)=== | ===Rapid Urease Testing (RUT)=== | ||
*Identifies active H.pylori infection through the organism's urease activity. | *Identifies active H.pylori infection through the organism's urease activity. | ||
*'''Procedure''' | *'''Procedure''' | ||
:*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 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. | :*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. | :*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. | *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 patchy distribution of H.pylori infection after antibiotics use. The sites include: | *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 | :*The body at the gastric angularis | ||
:*Greater curvature of the antrum | :*Greater curvature of the antrum | ||
*PPIs are withheld for 1-2 wk before performance of RUT as they reduce the sensitivity of test. | *PPIs are withheld for 1-2 wk before the performance of RUT as they reduce the sensitivity of the test. | ||
===Culture=== | ===Culture=== |
Revision as of 02:53, 18 January 2017
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]
Overview
Endoscopic Diagnostic Tests
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Endoscopic diagnostic tests are biopsy-based diagnostic methods for H.pylori infection. This include:
- Histology
- Rapid urease testing
- Culture
- Polymerase chain reaction
Histology
- Histology for H.pylori detection depends on:
- 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:
- Angularis
- 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)
- Identifies active H.pylori infection through the organism's urease activity.
- Procedure
- 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
- 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
Endoscopic testing | Advantages | Disadvantages |
---|---|---|
*1. Histology | Excellent sensitivity and specificity | Expensive and requires infrastructure and trained personnel |
*2. Rapid urease testing | Inexpensive and provides rapid results. Excellent specificity and very good sensitivity in properly selected patients | Sensitivity significantly reduced in the posttreatment setting |
*3. Culture | Excellent specificity. Allows determination of antibiotic sensitivities | Expensive, difficult to perform, and not widely available. Only marginal sensitivity |
*4. Polymerase chain reaction | Excellent sensitivity and specificity. Allows determination of antibiotic sensitivities | Methodology not standardized across laboratories and not widely available |