Helicobacter tests: types, reliability, preparation and results
The content of the article:
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Helicobacter tests
- PCR
- ELISA
- Immunoblotting
- Breathing tests
- Microbiological methods
- Preparation for analysis
- How the results are decoded
- Helicobacter pylori and its features
- Helicobacter pylori infection symptoms
An analysis for Helicobacter (Helicobacter pylori) is prescribed in the presence of symptoms of chronic gastritis and stomach ulcers, since it is this bacterium that is the causative agent of these diseases. What is it, when should a study be carried out, how to decipher the results and how to treat an infection?
Helicobacter tests
There are several ways to diagnose HP infection (abbreviated HP from Helicobacter pylori), they have different reliability and differ in time and cost. Which method is faster and cheaper, and which one will show the result more accurately?
Methods for laboratory diagnosis of Helicobacter pylori infection are divided into invasive and non-invasive. Invasive ones involve endoscopy with taking biomaterial (biopsy) and subsequent cytological examination.
Helicobacter tests can detect and quantify the presence of infection.
The most informative of the non-invasive tests are immunological studies, which determine the presence of antibodies to Helicobacter pylori in the blood, H. pylori antigen in the feces, PCR tests to identify the genetic material of the bacteria, and breath tests.
PCR
Polymerase chain reaction (PCR) is a molecular genetic study that allows you to identify DNA fragments of the causative agent of Helicobacter pylori. Fecal matter is used as a test biomaterial. During the analysis, a section of bacterial DNA is isolated from the biomaterial, which is then repeatedly duplicated on a special device - an amplifier. When the amount of DNA is sufficient for further detection, it is determined whether a genomic fragment characteristic of Helicobacter pylori is found in the sample. A positive result means the presence of Helicobacter pylori infection. PCR analysis allows you to confirm the presence of a foreign microorganism in the body with an accuracy of 90-95%. Normally, the genetic material of Helicobacter pylori is not found in the test material.
ELISA
Immunological methods do not directly determine the pathogen, but detect antibodies to its characteristic antigens.
The main method of blood analysis for antibodies is enzyme-linked immunosorbent assay (ELISA) - a quantitative determination of the level of antibodies of the IgA, IgM and IgG classes to Helicobacter pylori. ELISA also allows you to evaluate the effectiveness of therapy for infection. Thus, the production of IgM antibodies to Helicobacter pylori is a marker of the acute stage of the process. IgM disappears a few weeks after the initial infection. With the progression of the disease and its transition to a chronic form, antibodies of the IgA class are detected, then IgG. High levels of their concentration remain in the blood for a long time. The sensitivity of the method is 87-98%.
Immunoblotting
Immunoblotting is significantly inferior to other immunological methods both in cost and in the complexity of the analysis, but only with its help, with only the patient's blood serum, it is possible to obtain data on the properties of the Helicobacter pylori strain (based on whether it produces specific antigens CagA and VacA).
Breathing tests
Breathing test - determination of the products of urea hydrolysis by H. pylori urease in the patient's exhaled air. The study is based on the ability of bacteria to produce the hydrolytic enzyme urease. In the digestive tract, urease decomposes urea to carbon dioxide and ammonia. Carbon dioxide is transported to the lungs and released with air during breathing, its amount is recorded with a special device for urease analysis. Breathing tests for Helicobacter are divided into carbon and ammonia.
Microbiological methods
Microbiological and bacteriological methods are used less frequently, as they take more time. They involve bacteriological inoculation of feces, isolation of the pathogen culture and determination of its sensitivity to antibiotics. In the course of the study, the feces are placed in a growth medium favorable for the cultivation of Helicobacter colonies. After a certain period of time, the culture is examined under a microscope, noting the number of colonies and their properties.
The decision on the choice of the method is made by the attending physician. If an HP infection is detected in a patient, it may be advisable to examine the patient's family members.
Preparation for analysis
To pass the analysis for Helicobacter, no special training is required, but it is important to follow the general rules, since only correctly collected material guarantees the reliability of the result. As a rule, all tests are taken on an empty stomach, that is, after at least eight hours of abstinence from food. Before the study, you should exclude alcohol intake, smoking, consumption of fatty and fried foods. When collecting material yourself, for example, for stool analysis, it is important to avoid contamination, since any foreign inclusions (for example, detergents used to clean the toilet bowl or bedpan) can distort the result.
An important rule when taking tests: within a month before taking the material, the patient should not take antibiotics and drugs that stimulate gastric motility.
How the results are decoded
If a qualitative analysis was carried out (determination of the presence of Helicobacter bacteria in the body), then in the form of results there can be only two options - "negative" or "positive". If the analysis method involved a quantitative assessment, the rates of the results depend on the methodology, laboratory, units of measurement and other factors, therefore, only a doctor can interpret the analysis results, he also makes the final diagnosis and prescribes treatment.
Helicobacter pylori and its features
Until the 70s of the last century, it was believed that any bacteria that entered the stomach died under the influence of hydrochloric acid, lysozyme and immunoglobulin. In 1989, researchers were able to isolate and cultivate a spiral microorganism from the gastric mucosa of a patient suffering from gastritis - the bacterium Helicobacter pylori.
The name of the microorganism comes from "pylori", indicating its habitat (pyloric stomach), and the characteristics of the form - "helico", which means "spiral".
Infection with a bacterium usually occurs through contact with dirty surfaces, through saliva, airborne droplets, as a result of contact with an infected patient, non-compliance with personal hygiene rules, eating insufficiently clean vegetables and fruits, and water from contaminated sources.
After entering the body, the bacterium moves along the mucous membrane of the stomach with the help of flagella and is fixed on its walls. The microorganism produces substances that destroy the epithelial cells of the gastric mucosa, releases toxins that cause immune diseases. Trying to protect itself from a parasitic microorganism, the stomach increases the secretion of hydrochloric acid and substances that destroy its walls. However, the bacterium is able to survive for a long time in an acidic environment due to the enzyme it secretes - urease, which protects the microorganism from the effects of gastric juice.
In 1989, an infectious agent of gastritis and gastric ulcer was identified - the bacterium Helicobacter pylori
The appearance of clinical symptoms depends on the state of immunity. Among infected people, asymptomatic carriage is also found, since the microbe is capable of long-term parasitism without pronounced clinical manifestations and conflicts with the host's immune system. In this case, the bacterium takes an inactive form, increasing its activity when conditions favorable to it appear. However, even in an inactive state, the pathogenic microorganism can cause damage to the walls of the stomach and duodenum. The developing inflammatory changes can lead to mucosal atrophy and the development of malignant neoplasms.
Helicobacter pylori infection is associated with chronic gastritis, gastric ulcer and duodenal ulcer, malignant tumors of the stomach (adenocarcinoma, B-cell lymphoma).
Helicobacter pylori infection symptoms
The main signs that may indicate infection with Helicobacter pylori are typical symptoms of diseases of the gastrointestinal tract:
- pain in the epigastric region;
- bad breath;
- sour belching;
- heartburn, nausea, vomiting;
- loss of appetite;
- feeling of heaviness after eating;
- increased gas formation;
- prolonged constipation or loose stools, as well as their alternation.
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Anna Kozlova Medical journalist About the author
Education: Rostov State Medical University, specialty "General Medicine".
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