Modern medicine has specific diagnostic methods that make it possible to establish the etiology of diseases in humans based on the definition of the pathogen, genetically alien substances that stimulate the immune response, nucleic acids, as well as allergic and immune changes that occur due to his actions. Today, RIA is widely used in immunology and virology, that is, radioimmunoassay, the goals of setting, components, the course, the accounting of which, we will consider in this article. This assay is able to detect antigens as a result of their interaction with antibodies.
Definition
RIA is a method for diagnosing biologically active substances in liquids, which is based on the reaction of antigens with antibodies when using radionuclide-labeled analogous substances that have special binding systems. After their interactionan immune complex is formed, which is separated and its radioactivity is studied. It is known that radioimmunoassay is carried out using standard reagent kits.
Each reagent is able to determine the concentration of one specific substance. The biological fluid taken from a person is mixed with a reagent, after the incubation period, the free and bound radioactive substances are separated, then radiometry is carried out and the results are calculated. An isotope of iodine is used to label substances. It is marked and added in a certain amount.
Application
Radioimmune analysis has a wide application in medicine and microbiology. It is used to diagnose heart and vascular diseases, diseases of the endocrine and other body systems. RIAs are also often used to identify the cause of infertility, the pathology of fetal development. In oncology, this analysis is carried out in order to determine the markers of neoplasms in order to be able to monitor the effectiveness of treatment. In immunology, RIA is used to study the presence of immunoglobulins, enzymes, proteins, and so on in the blood. Today, this analysis allows you to detect the concentration of various hormones up to a millionth of one gram. Thus, radioimmunoassay is widely used in cardiology, oncology, endocrinology, gynecology and virology.
RIA Methods
It is customary to distinguish between several methods of analysis, depending on the naturereactions:
- The non-competitive method is characterized by such reaction components as standard and detectable antigens, buffer solution, isotope-labeled antibodies, certain antibodies that bind to the sorbent. An antigen is added to the antibodies to be tested. After incubation, antigen-antibody complexes appear, the sorbent is washed, labeled antibodies are added, which bind to the antigen in the complex. The radioactivity depends on the concentration of the antigen being tested.
- Competitive radioimmunoassay is driven by antigen competition. Here there are such components of the reaction as control and determined antigens, a buffer solution, certain antibodies that bind to the sorbent, as well as an isotope-labeled antigen. Diagnosis begins with the introduction of the antigen that is being examined. An antigen-antibody complex is formed on the sorbent. Then the sorbent is washed, and the labeled antigen is injected. In doing so, it binds to the antibody. With the help of counters, the reaction and the amount of radioactivity are measured. It will be in inverse proportion to the amount of antigen in the sample.
- The indirect method is the most common. In this case, the radioimmunoassay of the reaction components has such as control and test serum, antigens or antibodies that are bound on the sorbent, antibodies labeled with isotopes, buffer solutions. Antibodies or antigens that are diagnosed react with antigens or antibodies that are bound to the sorbent. Then the incubate is removed, labeled antibodies are injected, which bind toantigen-antibody complexes.
Analysis Methodology
So, radioimmunoassay is carried out using special reagents. The sets are standard, so any errors or violations are not allowed. Diagnostic results are reliable. The analysis is carried out in the morning, for this they take venous blood from a person. In the laboratory, serum is separated from the blood, which will be used for RIA. This serum is mixed with reagents. The resulting mixture is incubated at a given temperature in a thermostat.
Free and bound isotopes are separated in the resulting mixture. After that, the received material is examined, and the results are calculated. The radioimmunoassay mechanism has several options. The technique described above is a liquid-phase RIA, since all components are in a liquid state. There is RIA and solid-phase, where antibodies are placed in a carrier that does not dissolve in liquid.
Availability of diagnostics
The use of this diagnostic method in medicine is becoming more and more popular every year. Recently, radioimmunoassay has become a standard diagnostic method that can be prescribed by a doctor when making a final diagnosis. For a long time this type of analysis was carried out only in laboratories, today it has become a common research method. But RIA requires the use of expensive equipment (gamma counters), and reagent kits have a short service life. All this is the main drawback of such an analysis, which determines itsexpensive cost.
In addition, RIA has recently begun to supplant more modern research methods that do not require interaction with isotopes. These include enzyme immunoassay. Thus, RIA is desirable in many clinics. It has long been used in large cities and diagnostic centers, but in ordinary hospitals in small towns this analysis is practically not used because of its high cost.
Dignity of RIA
Radioimmunoassay has many advantages. It is quite specific and has a high sensitivity, which makes it possible to determine the presence of biologically active substances in incredibly small quantities. This analysis is carried out very simply, a person is only required to donate venous blood. Test results are 100% accurate and ready the very next day. RIA can also be easily automated. Thus, this analysis allows you to identify proteins that are waste products of infectious bacteria, which indicates the presence of infection in the body.
Diagnosis in Virology
The most promising RIA is for virology, because it allows you to quickly identify viral pathogens. This is due to the fact that in recent years the incidence of various infections has been growing, which are spreading at a high speed, causing mortality among people. This is especially true for countries that do not have a highsocial and economic development (the countries of the Far East), radioimmunoassay is simply indispensable here. Microbiology also uses this diagnostic method to detect infectious diseases caused by pathogenic bacteria. For example, RIA is widely used to detect typhoid fever. In the first days of the disease, before the appointment of treatment, it is necessary to conduct a study of feces and vomit. However, the diagnostic results will be obtained after a long time. Here RIA comes to the rescue, the analysis allows you to identify the causative agent of the disease in a short time. A person donates blood, the next day the results of the study are ready. This analysis helps in making an accurate diagnosis.
Results
Radioimmunoassay is currently one of the most sensitive diagnostic methods. It is used to analyze any substance against which antibodies can be obtained. This method makes it possible to make many samples in the smallest volume of the investigated liquid, as well as to record the results in the shortest possible time, since it can be fully automated. This analysis was developed in the 1950s by Solomon Burson. Thirty years later, it became widespread. To date, there is no one hundred percent alternative to RIA, since the analysis has a high sensitivity. RIA is used in various branches of medicine, as well as in microbiology and virology.
Finally
The use of the method in virology is very relevant today, as it givesthe ability to investigate the spread of infections, make an accurate diagnosis and prescribe specific treatment. This problem is especially relevant for countries that have a low level of economy and social development. Also, this analysis allows you to detect the amount of hormones and enzymes in the human body. In order to obtain reliable results, the researcher only needs to donate blood for analysis. Medicine does not stand still, along with radioimmunoassay, new research methods appear, but RIA continues to be one of the leaders in medical diagnostics.
