Helicobacter pylori, antibodies total
Why this test?
To diagnose diseases caused by H. pylori and control their treatment:
Antral and fundal gastritis;
Duodenal or stomach ulcers.
In what cases is it prescribed?
When examining a patient with first-onset signs of dyspepsia (primary H. pylori infection), especially if endoscopy is not planned.
When examining a patient with a history of dyspepsia, if H. pylori therapy was not prescribed (or if antibiotics active against H. pylori were not used for another reason).
At the initial diagnosis of helicobacteriosis and 6 months after the end of the course of its therapy.
H. pylori is a gram-negative, facultatively anaerobic microorganism capable of infecting the mucous membrane of the stomach and duodenum. In most cases, infection with H. Pylori (helicobacteriosis) is permanent and chronic.
Helicobacteriosis is very common: the bacterium H. pylori can be detected in 50% of people on the globe. At the same time, H. pylori-associated diseases (gastritis, gastric or duodenal ulcer, gastric adenocarcinoma, MALT lymphoma) occur only in 15-20% of infected patients. A feature of these diseases is their favorable prognosis, provided their early diagnosis and complete eradication of H. pylori. Laboratory research methods are of leading importance in the diagnosis of helicobacteriosis.
There are several methods for detecting H. pylori. Direct methods allow direct detection of the microorganism itself. Most direct methods require a sample of mucosal tissue (biopsy) and/or stomach and duodenal contents (aspirate), which are usually obtained during an endoscopy. Thus, direct research methods are usually invasive. In contrast, indirect methods detect not the microorganism itself, but indirect signs of infection, such as specific antibodies in blood serum (serological tests) or the retention of a labeled carbon atom in exhaled air (respiratory urease test). Since indirect tests do not require an endoscopic examination, they are called non-invasive. Both direct and indirect tests for H. pylori have their advantages and disadvantages. Accurate diagnosis of helicobacteriosis requires several tests at once. In this regard, a comprehensive analysis that includes all necessary tests for H. pylori is especially convenient for the doctor and the patient.
One of the most sensitive methods for detecting H. pylori is real-time polymerase chain reaction (RT-PCR). RT-PCR is a method of molecular diagnostics that allows detection of fragments of genetic material (DNA) of an infectious agent in biological material (for example, in a tissue sample). Since the analysis is based on the detection of genetic material, RT-PCR allows detecting the presence of any forms of H. pylori (not only active spiral-like, but also inactive coccal, uncultivated), as a result of which the study is characterized by a very high sensitivity, which exceeds the sensitivity of the bacteriological method sowing Theoretically, the presence of 1 DNA molecule is sufficient for RT-PCR. In practice, the concentration of the pathogen in the sample should be about 10-100 CFU / ml. Such a high sensitivity of the test means that receiving a negative test result allows you to exclude H. pylori as the cause of the disease. This is of fundamental importance in the differential diagnosis of NSAID-associated, stress and ischemic gastritis and ulcers.
It should be noted that, despite the very high sensitivity of the test (85-98%), false negative results are still possible. So, for example, falsely negative results can be obtained if the bacterial load is very low (for example, against the background of taking some antibiotics). Misdiagnosis can be avoided by combining this direct test with serological studies.
H. pylori infection is accompanied by a significant increase in IgG and IgA class immunoglobulins in blood serum. These immunoglobulins (antibodies) are determined in the blood using indirect tests. IgG is detected in 95-100% of cases of helicobacteriosis, and IgA - in 68-80%. The study allows you to determine the titer of antibodies, that is, it is quantitative. As a rule, high antibody titers are more characteristic of an active, ongoing infection. It should be noted, however, that there is no clear correlation between the antibody titer and the severity of the infection.
Serological tests, like the RT-PCR method, have some limitations. Yes, the result of the analysis depends on the features of the patient's immune response. The immune response of patients taking cytostatic drugs and the elderly is characterized by reduced production of specific antibodies (any, including H. pylori). For this reason, to avoid diagnostic errors, it is advisable to supplement serological tests with direct tests. This feature was taken into account when compiling a comprehensive analysis for H. pylori.
Thus, a comprehensive test for H. pylori is a combination of necessary and sufficient tests for the detection of this microorganism. Complex analysis is not intended to monitor treatment. The result of both RT-PCR and IgG and IgA immunoglobulins will remain positive even in case of complete eradication of H. pylori. A false-positive result of RT-PCR in this case is due to the ability of this method to detect DNA of any, even destroyed, microorganisms, a false-positive result of serological tests is due to the peculiarities of the dynamics of the immune response.