Helicobacter pylori infection diagnostic tests: Difference between revisions
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==Overview== | ==Overview== | ||
Endoscopic diagnostic tests are biopsy-based diagnostic methods for ''[[H. pylori]]'' infection. These include [[histology]], [[rapid urease testing]], [[culture]] and [[polymerase chain reaction|polymnerase chain reaction (PCR)]]. | |||
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{| class="wikitable" | {| class="wikitable" | ||
| colspan="4" | | | colspan="4" | | ||
* 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. | * In patients who have not been on a [[proton pump ionhibitor|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]]''. | ||
|- | |- | ||
| colspan="4" | | | colspan="4" | | ||
* For patients who have been taking a PPI, antibiotics, or bismuth, endoscopic testing for H.pylori should include biopsies from the gastric body and antrum for histology with or without rapid urease testing. | * For patients who have been taking a [[proton pump inhibitor|PPI]], [[antibiotics]], or [[bismuth]], endoscopic testing for ''[[H. pylori]]'' should include biopsies from the gastric body and antrum for histology with or without rapid urease testing. | ||
|- | |- | ||
| colspan="4" | | | colspan="4" | | ||
* 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. | * Though culture or [[polymerase chain reaction|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. This include: | Endoscopic diagnostic tests are biopsy-based diagnostic methods for ''[[H. pylori]]'' infection. This include: | ||
*Histology | *[[Histology]] | ||
*Rapid urease testing | *Rapid urease testing | ||
*Culture | *Culture | ||
*Polymerase chain reaction | *[[Polymerase chain reaction]] | ||
===Histology=== | ===Histology=== | ||
*Histology for H.pylori detection depends on: | *Histology for ''[[H. pylori]]'' detection depends on: | ||
:*Site, number, and size of gastric biopsies | :*Site, number, and size of gastric biopsies | ||
:*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 is taken from different sites. They are: | *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 affected by the use of medications such as bismuth, antibiotics, and PPI. | *The sensitivity of histology is greatly affected by the use of medications such as [[bismuth]], [[antibiotics]], and [[proton pump inhibitor|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|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 [[proton pump inhibitors|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: | *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 the performance of RUT as they reduce the sensitivity of the test. | *[[Proton pump inhibitors|PPIs]] are withheld for 1-2 wk before the performance of RUT as they reduce the sensitivity of the test. | ||
===Culture=== | ===Culture=== | ||
*Culture is not as sensitive as RUT or histology. | *Culture is not as sensitive as RUT or histology. | ||
*Highly specific method for identifying active H.pylori infection. | *Highly specific method for identifying active ''[[H. pylori]]'' infection. | ||
*It is also used to determine antibiotic sensitivities and resistance. | *It is also used to determine antibiotic sensitivities and resistance. | ||
===Polymerase Chain Reaction (PCR)=== | ===Polymerase Chain Reaction (PCR)=== | ||
*PCR is highly specific and more sensitive than other biopsy-based diagnostic techniques. | *[[PCR]] is highly specific and more sensitive than other biopsy-based diagnostic techniques. | ||
*It is also used to identify mutations associated with antimicrobial resistance. | *It is also used to identify mutations associated with antimicrobial resistance. | ||
*This method is not standardized across laboratories | *This method is not standardized across laboratories | ||
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!Disadvantages | !Disadvantages | ||
|- | |- | ||
|*1. Histology | |*1. [[Histology]] | ||
| | | | ||
* Excellent sensitivity (>95%) and specificity (95%) | * Excellent sensitivity (>95%) and specificity (95%) | ||
| | | | ||
* Expensive and requires infrastructure and trained personnel | * Expensive and requires infrastructure and trained personnel | ||
* Detection improved by use of special stains- e.g. the Warhin-Starry silver stain, or the cheaper | * Detection improved by use of special stains- e.g. the [[Warhin-Starry silver stain]], or the cheaper [[giemsa stain]] protocol | ||
|- | |- | ||
|*2. Rapid urease testing | |*2. Rapid urease testing | ||
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* Sensitivity significantly reduced in the posttreatment setting | * Sensitivity significantly reduced in the posttreatment setting | ||
|- | |- | ||
|*3. Culture | |*3. [[Culture]] | ||
| | | | ||
* Excellent specificity. | * Excellent specificity. | ||
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* Experience/ expertise required | * Experience/ expertise required | ||
|- | |- | ||
|*4. Polymerase chain reaction | |*4. [[Polymerase chain reaction]] | ||
| | | | ||
* Excellent sensitivity and specificity. | * Excellent sensitivity and specificity. | ||
Revision as of 19:46, 23 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 are biopsy-based diagnostic methods for H. pylori infection. These include histology, rapid urease testing, culture and polymnerase chain reaction (PCR).
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)
- 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 |
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| *2. Rapid urease testing |
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| *3. Culture |
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| *4. Polymerase chain reaction |
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