Diagnosis ofHelicobacter pylori: What should be the gold standard?

Abstract

Since the discovery of Helicobacter pylori (H. pylori) in 1983, numerous detection methods for the presence of the bacterium have been developed. Each one of them has been associated with advantages and disadvantages. Noninvasive tests such as serology, (13)C urea breath test (UBT) and stool antigen tests are usually preferred by the clinicians. Serology has its own limitation especially in endemic areas while (13)C UBT is technically very demanding. The stool antigen detection method, although specific, is usually associated with poor sensitivity. The (13)C UBT is believed to be specific, but with present revelation of the fact that stomach is colonized by many other urease producing bacteria makes it questionable. Histology, culture, rapid urease test and polymerase chain reaction (PCR) are the tests which are carried out on antral biopsies collected by invasive means. Histology has been proposed to be very sensitive and specific but the question is how by simply looking the morphology of the bacteria in the microscope, one can claim that the curved bacterium is exclusively H. pylori. Rapid urease test (RUT), the doctor's test, is also challenged because the presence of other urease producing bacteria in the stomach cannot be denied. Moreover, RUT has been reported with poor sensitivity specially, when density of the bacterium is low. Isolation of H. pylori is essential to investigate its growth requirements, antibiotic susceptibility testing, studying virulence factor to develop vaccine and many more explorations. It has also got several disadvantages i.e., special condition for transporting, media, incubation and few days waiting for the colonies to appear, apart from the speed essentially needed to process the specimens. Till date, majority of the microbiological laboratories in the world are not equipped and trained to isolate such fastidious bacterium. The option left is PCR methods to detect H. pylori's DNA in gastric mucosa, gastric juice, saliva, dental plaques and environmental specimens. There are speculations for false positivity due to detection of non-pylori Helicobacters due to genetic sharing; and false negativity due to low bacterial counts and presence of PCR inhibitors. However, specimen collection, transportation and processing do not require speed and special conditions. PCR based diagnosis may be considered as gold standard by designing primers extremely specific to H. pylori and targeting at least more than one conserved genes. Similarly specificity of PCR may be improved by use of internal Primers. Further, nested PCR will take care of false negatives by countering the effect of PCR inhibitors and low bacterial counts. Therefore, nested PCR based methods if performed properly, may be proposed as gold standard test.

Comparative Evaluation of RUT, PCR and ELISA Tests for Detection of Infection with Cytotoxigenic H. pylori

“…Although PCR could be performed even with a traces of bacterial DNA, it is mainly considered as an invasive method that needs biopsy. 16 On the other hand simple breath tests (UBT), serology and stool antigen test as well as Enzyme-Linked Immunosorbent Assay (ELISA) are known as noninvasive assays which are usually used for patients who are not advised undergoing gastroscopy. 17 To date, several commercially available ELISA kits have been used for detection of H. pylori infection which differs in target antigens and antibody preparations.…”

The importance of Helicobacter pylori in the development of gastric MALT lymphoma — induction of proliferation and immune suppression

“…Confirming H. pylori status in people with diagnosed GML is a routine procedure [39]. It is suggested that besides detecting such bacteria, an important diagnostic element may also be in determining the H. pylori virulence profile.…”

“…For this reason, H. pylori infection should be confirmed in each patient diagnosed with GML. The diagnosis should be based on invasive and noninvasive tests including measuring IgG, IgM, IgA antibodies, monoclonal stool antigens detection, the 13 C-urea breath test, microbes culture and histochemical testing [39]. H. pylori eradication therapy should rely on highly effective antibiotics with due consideration given to possible resistance in bacterial strains [5].…”

Letter: effect of proton pump inhibitor use on invasive detection ofHelicobacter pylorigastritis - authors' reply

“…However, while PCR tests for antibiotic resistance and pathogenicity are well established and commercialised in Europe and Asia, the large numbers of apparent 'false positives' (positive PCR in histologically normal biopsies) has limited its clinical applications as markers of infection. 6 …”

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