Recent Approaches in the Diagnosis of Helicobacter Pylori induced Gastritis

Endoscopy: A Pivotal Approach in Diagnosis of H. pylori

Upper GI endoscopy is a procedure in which an endoscope, a flexible tube with a camera to see the lining of your upper GI tract, including your oesophagus, stomach, and duodenum. During upper GI endoscopy, biopsies are obtained by passing an instrument through the endoscope to take small pieces of tissue from stomach lining, to diagnose gastritis or gastropathy, determine the cause, and manage complications.

A gastroscopy may be performed, which is a type of upper gastrointestinal endoscopy. The procedure involves an endoscope being inserted into the patient’s stomach to examine the internal walls of the oesophagus and stomach. This procedure is often used to confirm a diagnosis. If metaplasia (pre-cancerous changes) or gastric cancer is suspected, a biopsy sample may also be taken from the affected area.

Mucosal biopsy samples can also be used to check for H. pylori. The sample is placed on a reaction strip or agar gel that contains urea, a pH indicator and a buffer. If H.pylori is present, the urea is converted to ammonia and bicarbonate, which is picked up as a change in colour. The sensitivity and specificity of this test is 90% and 100%, respectively, providing the patient is not taking a proton pump inhibitor or antibiotic. The test is also not reliable in individuals with an acute GI bleed

Urea breath test

Because of high sensitivity and specificity, UBT is a very attractive method to measure the H. pylori active infection. At least for asymptomatic subjects, the UBT is a gold standard method. Another preference of UBT is that the method is free of sampling errors (lack of endoscopic surgery).  Overall, the specificity and sensitivity of the UBT are mostly more than 95%. Although these high rates for both sensitivity and specificity are an advantage for this test, lack of data on antibiotic resistance and further analysis is the main limiting feature of this popular method to detect active H. pylori infection. In recent years, stool antigen test (SAT) and UBT became more acceptable diagnostic tests to detect active H. Pylori Infection.

Faecal Antigen Test/ Stool Antigen Test

The faecal antigen test, which detects H.pylori in stool samples, is available as a monoclonal and polyclonal assay. The sensitivity and specificity of the monoclonal assay is 96% and 97% respectively and for the polyclonal assay, both sensitivity and specificity are more than 90%.

Although the SAT is an accurate and precise method this accuracy is influenced by several limiting factors: upper gastrointestinal bleeding, antibiotic consumption, bowel movement, and also proton pump inhibitors (PPIs) uptake. This non-invasive and almost cheap test became recommended whenever UBT was not available. There are two major preferences for SAT in comparison with UBT; less expensive chemicals and materials and also not high technology equipment are necessary.

Upper GI series

Upper GI series or Barium swallow is used to check for signs of gastritis or gastropathy. An upper GI series is a procedure in which a doctor uses x-rays and a chalky liquid called barium to view upper GI tract.

Serological Tests

Done by using different bacterial components include whole cell lysate, specific outer membrane proteins, LPS, heat shock protein (HSP), catalase, and cag A protein and many of the adhesions were applied to induce specific antibodies in the host for facilitating the serological assay.

The clinical importance of this test emerges when antibiotics and PPIs consumption are reported. Indeed, false negative results observed for other methods can have different response using serologic analysis. Because of acceptable sensitivity and specificity rates observed in many commercial IgG-bases tests exist and have been validated in recent years. Taking together, the antibody-based examination cannot guarantee the accuracy of reported H. pylori status following the antibiotic treatment; thus further analysis is needed.

Rapid Urease Test

Rapid urease test (RUT) is a one of the cheapest but rapid diagnostic tests. The main biologic basis of this diagnostic test is to evaluate the presence of urease enzyme in clinical specimens shipped to the laboratories. Staphylococci and streptococci are the other major urease-producers present in the gastric mucosa and may interfere with the detection of H. pylori based on the urease activity.

Culture

The main superiority of bacterial culture for H. pylori is the possibility of antibiotic susceptibility tests to choose proper antibiotics in the treatment of subjects and avoiding a new generation of antibiotic resistance among the symptomatic animals. Successfulness of this culture process made this approach as the gold standard in the diagnosis of H. pylori infection.

As a general rule, H. pylori needs blood or lysed blood supplements to grow optimally on agar plates. Currently, Wilkins Chalgren agar, Brain heart agar, and Columbia and Brucella agars are most used base media to propagate H. pylori culture in routine diagnosis. Because of the high risk of contaminating microorganisms including gram-positive microorganisms, fungi, and yeasts, using selective medium became a universal rule to have typical H. pylori colonies on the plates.

PCR

PCR-based methods are applied to detect H. pylori infections in large variety of environmental and clinical samples including water, food, vegetables, human saliva, stool, gastric juice and biopsies, and dental plaques. Positive result from a specific PCR approach can easily replace other time-consuming and expensive tests.

References

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