To conduct a comprehensive assessment of the state of the body, the ELISA method of diagnosis is used. An enzyme-linked immunosorbent assay is designed to diagnose infectious, hematological, primary and secondary immunodeficiencies.
What is ELISA
Many patients are interested in ELISA: what is it, what is the study done for. Enzyme-linked immunosorbent assay has been used relatively recently. Initially, antigenic structures were studied with its help, and it was carried out only for scientific purposes. Then scientists came to the conclusion that with the help of enzymes specific antibodies can be identified that occur in response to an ongoing disease.
Initially, this technique was used only by narrow-profile medical institutions, mainly at blood transfusion stations. Of particular importance is the ELISA method for detecting HIV infection.
Today, this method has a wide scope. Modern laboratories use it to diagnose:
- tumors;
- hormonal disorders;
- infections
- chronic or previous infectious processes;
- helminths.
If an infectious process occurs in the body, then this type of diagnosis is considered the most optimal for determining the type of disease.
The essence of the method and its types
ELISA method - what is it, what is the essence of this type of research? This and many other questions interest patients. The basis of this diagnostic method is the binding of the body's immune cells to the antigens of the causative agents of the infection. The resulting complex is determined using a special enzyme.
To understand the principle of the ELISA method, you need to know how the antigen-antibody reaction proceeds. Antigen - a molecule of protein origin that is foreign to the body, which penetrates with the infection. Foreign blood particles that do not coincide in the group are also considered antigens. In the body, they provoke an immune response aimed at protecting against foreign substances. Therefore, the human body produces antibodies - immunoglobulins that can attach to antigens, forming an immune complex. Such compounds are much more easily recognized and destroyed by immunity cells.
The reaction to the presence of such immune complexes is carried out in the laboratory, using ready-made compounds to determine whether there are similar ones in the blood.
The essence of the ELISA method is quite simple, but due to the fact that a blood test is performed to detect many infections and diseases, there are several varieties of it. Each differs in the layout and scope. It can be direct or indirect ELISA. The direct method implies that immobilized antibodies that react with antigens are used. The main advantage of this method is that all processes can be automated, which means that diagnostics take a little time.
The indirect method implies that antibodies of a secondary nature are used. And on the solid phase, the antigen is immobilized. The analysis allows you to identify antibodies to various antigens. This helps to achieve a more accurate result, but the method is difficult.
Research benefits
ELISA laboratory tests have many advantages in comparison with other diagnostic methods. The main ones include:
- high sensitivity;
- storage stability of ingredients;
- speed of diagnosis;
- a small amount of test material can be used;
- it is possible to automate all processes;
- infection can be detected in the earliest stages.
This diagnostic method is universal, therefore suitable for mass screening. With the help of the analysis, it is possible to trace the dynamics of the course of the infectious process.
Indications for analysis and sampling
A study using the ELISA method can be prescribed for suspected many diseases:
- acute and chronic infections, sexually transmitted diseases;
- the presence of parasites;
- autoimmune pathologies;
- oncological diseases;
- to determine hormone levels.
Venous blood is examined for antibodies. Before the analysis, elements that can complicate the study are isolated from it. Other biological fluids may be sampled.
To get the most accurate information, blood sampling is performed on an empty stomach. If the procedure was prescribed to determine a latent infection, then several weeks before the analysis, you need to stop taking antibacterial and antiviral drugs. Depending on the equipment of the laboratory where the material was taken, the result can be obtained within 24 hours. In emergency cases, this time is reduced to several hours.
Syphilis test
Using the ELISA method helps to determine the presence of many infections in the body, in particular syphilis. For the study, blood is taken from an empty stomach vein. Then a study is carried out that helps to determine not only the presence of the disease in the body, but also the exact timing of its onset, since during the course of the disease, some antibodies are replaced by others in a strictly defined order.
In the acute phase, indicating a prolonged course of the disease, or with an exacerbation of a chronic infection, type M immunoglobulins will be detected in the blood. The presence of type A immunoglobulins indicates that the infection lives in the body for more than 4 weeks. Group G immunoglobulins indicate the height of the disease or previous treatment.
The degree of color of the holes assesses the intensity of the course of the infectious process, since its saturation depends on the number of formed immune complexes.
HIV test
The ELISA method is also used to test for HIV infection. Diagnosis in this case has certain features that are associated with the course and progression of the disease. This research method is considered the most acceptable for determination, however, it should be carried out no earlier than a month after exposure to risk factors. This is due to the presence of an incubation period that runs from 45 days to 6 months. That is why the analysis must be repeated after six months.
A positive result is considered if antibodies were detected during the initial study. In this case, the analysis is repeated six months later, if again the result is positive, then the study is carried out using highly specific test systems.
Parasite analysis
Quite often, doctors prescribe an enzyme immunoassay to determine the presence of parasites in the body. Using this research method, you can determine:
- ascariasis;
- giardiasis;
- toxoplasmosis and others
ELISA diagnostic blood is used to detect parasites and their metabolic products, as well as immunoglobulins. The effectiveness of this method is 90% and helps to trace the dynamics of the development of processes.
Disadvantages of the method
Despite all the advantages, there are also disadvantages of the ELISA method. The main disadvantage is that during the study, the doctor must have an assumption about the disease in advance.
When diagnosing infectious diseases, there is no way to accidentally find the pathogen and determine its enzyme-linked immunosorbent properties. The test only indicates the presence of antibodies in the patient’s blood. In addition, this is a rather expensive analysis.
Decryption analysis
The result of a qualitative ELISA will be either the presence of antibodies, or their absence in the blood. If a quantitative analysis is carried out, then the concentration of antibodies can be expressed either in numerical value or in a certain number of + signs.
In addition, indicators such as:
The IgM indicator indicates the occurrence of an acute infectious process in the body. Its complete absence may indicate the absence of the causative agent of the disease or its transition to the chronic stage.
An IgA score for a negative IgM test indicates a chronic or latent infection. The simultaneous presence of IgM and IgA indicates that the disease is in an acute stage. The presence of IgG indicates the transition of the disease to the chronic stage or a complete recovery and the development of immunity.
Now there are special ELISA tests that can be carried out independently.