Helicobacter pylori infection diagnostic tests

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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

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.

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.

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.

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 (>95%) and specificity (95%)	Expensive and requires infrastructure and trained personnel Detection improved by use of special stains- e.g. the Warhin-Starry silver stain, or the cheaper giemsa stain protocol
*2. Rapid urease testing	Inexpensive and provides rapid results. Excellent specificity (98%) and very good sensitivity in properly selected patients. Excellent specificity (99%)	Sensitivity significantly reduced in the posttreatment setting
*3. Culture	Excellent specificity. Allows determination of antibiotic sensitivities	Expensive, difficult to perform and not widely available. Poor sensitivity if adequate transport media are not available Experience/ expertise required
*4. Polymerase chain reaction	Excellent sensitivity and specificity. Allows determination of antibiotic sensitivities	Methodology not standardized across laboratories and not widely available Considered experimental