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 polymerase 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
- 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.[2]
- 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:[1][3]
- 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.[4]
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.[6]
- 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:[7]
- 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.[8]
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 |
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*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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References
- ↑ 1.0 1.1 el-Zimaity HM (2000). "Accurate diagnosis of Helicobacter pylori with biopsy". Gastroenterol Clin North Am. 29 (4): 863–9. PMID 11190070.
- ↑ Dixon MF, Genta RM, Yardley JH, Correa P (1996). "Classification and grading of gastritis. The updated Sydney System. International Workshop on the Histopathology of Gastritis, Houston 1994". Am J Surg Pathol. 20 (10): 1161–81. PMID 8827022.
- ↑ van IJzendoorn MC, Laheij RJ, de Boer WA, Jansen JB (2005). "The importance of corpus biopsies for the determination of Helicobacter pylori infection". Neth J Med. 63 (4): 141–5. PMID 15869042.
- ↑ Woo JS, el-Zimaity HM, Genta RM, Yousfi MM, Graham DY (1996). "The best gastric site for obtaining a positive rapid ureas test". Helicobacter. 1 (4): 256–9. PMID 9398877.
- ↑ Uotani T, Graham DY (2015). "Diagnosis of Helicobacter pylori using the rapid urease test". Ann Transl Med. 3 (1): 9. doi:10.3978/j.issn.2305-5839.2014.12.04. PMC 4293486. PMID 25705641.
- ↑ Midolo P, Marshall BJ (2000). "Accurate diagnosis of Helicobacter pylori. Urease tests". Gastroenterol Clin North Am. 29 (4): 871–8. PMID 11190071.
- ↑ Chey WD, Woods M, Scheiman JM, Nostrant TT, DelValle J (1997). "Lansoprazole and ranitidine affect the accuracy of the 14C-urea breath test by a pH-dependent mechanism". Am J Gastroenterol. 92 (3): 446–50. PMID 9068466.
- ↑ Laine L, Estrada R, Trujillo M, Knigge K, Fennerty MB (1998). "Effect of proton-pump inhibitor therapy on diagnostic testing for Helicobacter pylori". Ann Intern Med. 129 (7): 547–50. PMID 9758575.