Immunoenzymatic blood test with interpretation of indicators. What is IFA? Enzyme immunoassay method: essence, principle, disadvantages What does blood mean for ifa

Content

To assess the body's ability to resist infectious diseases or to determine the phase of the pathology, a blood test is used. The ELISA method occupies an important place among laboratory studies, it helps to comprehensively study the activity of the protective function of the blood, determine immunodeficiency in infectious diseases, blood ailments, hormonal, autoimmune processes.

What is an enzyme immunoassay

This method refers to laboratory studies, determines the presence of protective blood factors of a protein nature (antibodies) to certain disease-causing agents (antigens). Immunoenzyme analysis of blood determines immunoglobulins, which can be detected in the form of immunocomplexes. They appear when complex neurohumoral reactions of human immune defense occur, which become a response to the introduction of foreign antigens.

Specific antibodies are produced in the body against each type of pathogen. Further, the binding of a pathological microorganism or antigen occurs, a complex compound "antigen-antibody" is formed. Then it is neutralized, enzymatic lysis occurs, the reaction of phagocytosis, and the process ends with the withdrawal from the body. The presence of specific complexes, determined by ELISA, indicates the type of pathogen, a harmful substance in a patient.

Immunoglobulin classes

Scientists have discovered and studied 5 types of immunoglobulins: IgE, IgD, IgG, IgM, IgA. There are other classes, but they are still at the stage of research, and their role has not been fully elucidated. In practical medicine, A, M, G are important. Informativeness, accuracy of determination is based on the time intervals for which they appear, reach a maximum and disappear.

Indications for blood testing by ELISA

With the help of this analysis, it is possible to evaluate the effectiveness of treatment, conduct a comprehensive study before transplant operations, determine the state of immunodeficiency and antibodies to more than 600 types of allergens. A blood test using ELISA is used as an additional method for detecting cancer cells. An analysis is prescribed if it is necessary to detect antibodies to microbes that provoke venereal pathologies:

trichomoniasis;
syphilis;
toxoplasmosis;
mycoplasmosis;
ureaplasmosis.

With helminthic invasions in the analysis of ELISA, an increase in the number of immunoglobulins will be noted. Research is being conducted to confirm the presence of the patient:

Epstein-Barr virus;
herpetic infections;
cytomegalovirus;
groups of viral hepatitis.

An enzyme immunoassay is not the only option for determining immunoglobulins. Sometimes for this study, cerebrospinal fluid, vitreous tissue, and amniotic fluid are taken. When using blood, it is collected from the cubital vein using an injection needle. It is necessary to take an analysis on an empty stomach; before ELISA, it is not recommended to take medications that can affect the result. You should give up alcohol, smoking, drug use before donating the biomaterial. Test result options:

With negative indicators of immunoglobulins IgG, IgM, IgA, doctors talk about the absence of pathology or the initial stage. The same result (negative) will be after a full recovery after a long period.
If IgG is positive, but IgM and IgA are not detected, this indicates the formation of immunity after vaccination or an infectious disease.
With high titers of IgM and negative IgA, IgG, an acute infectious disease is diagnosed.
With a positive indicator of IgG, IgM, IgA, doctors talk about the acute phase of a relapse of an existing chronic disease.
With a chronic infection that is at the stage of subsiding (remission), the ELISA analysis shows negative IgM titers, and IgA and IgG will be positive.

Advantages and disadvantages of ELISA analysis

The main negative point of this study is the possibility of obtaining false positive or false negative results. The reason for the unreliability is the intake of medicines, technical shortcomings of the laboratory. The process of metabolic disorders in the body can falsify the analysis. The main advantages of ELISA analysis are:

accuracy, diagnostic specificity;
low cost of analysis;
the speed of obtaining results;
the possibility of dynamic control of the stage of pathology, the effectiveness of treatment;
ease of research;
the ability to perform mass examinations of foci of infection;
painlessness, safety for the patient;
application in information technology processing.

Video

Enzyme-linked immunosorbent assay (ELISA) is carried out for a comprehensive assessment of the protective functions of the body. During the study, the number and properties of immune cells, the presence of the necessary antibodies are determined. ELISA blood test is performed to diagnose infectious, hematological, autoimmune diseases, primary and secondary immunodeficiencies. Consider what a blood test is by ELISA, and what indications exist for this study.

What it is

An ELISA blood test is a laboratory method that detects antibodies or antigens in a blood sample. This study is used to detect the level of immunoglobulins, immunological complexes, hormones.

Indications for analysis

For the appointment of an ELISA blood test, there are the following indications:

diagnosis of sexually transmitted infections - ureaplasma, mycoplasma, chlamydia, trichomonas, syphilis;
diagnosis of viral diseases - cytomegalovirus, herpes, hepatitis, Epstein-Barr virus;
determining the level of hormones;
diagnosis of oncological diseases;
determination of immunodeficiency;
diagnosing allergies;
preoperative comprehensive examination before organ transplantation;
assessment of the effectiveness of therapy.

Method principle

The principle of operation of the enzyme immunoassay method is based on the determination of specific protein-antibodies in the blood - immunoglobulins. Immunoglobulins are produced by the human immune system when antigens (foreign microorganisms) enter the body. These immune molecules bind to a variety of infectious agents in the body and neutralize them.

Immunoglobulins have an important characteristic - specificity. Due to this, they can bind to a specific antigen, forming an antigen-antibody complex. During an ELISA blood test, it is this complex that is determined qualitatively and quantitatively.

There are five classes of immunoglobulins. But usually three classes are defined - immunoglobulins A, M, G. These antibodies accumulate in the body at different times from the moment of infection.

Immunoglobulins class M (IgM) appear in the blood very first on the fifth day from the moment of infection. They are in the body for 5-6 weeks, then disappear from the bloodstream. IgM antibodies indicate an acute period of the disease or an exacerbation of the disease in its chronic course.
Approximately 3-4 weeks after infection, immunoglobulins appear in the blood class G (IgG). They can exist in human blood for several months or even years. According to the decoding of the ELISA blood test, if in two blood samples taken consecutively two weeks later, the amount of IgG immunoglobulins is increased, they speak of a current infection or reinfection - re-infection with the same infection.
Immunoglobulins class A (IgA) can be detected by this research method 2–4 weeks after infection or exacerbation of an infectious disease. Of these, only 20% circulates in the blood, the rest are secreted by the mucous membranes. IgA antibodies disappear from the bloodstream 2-8 weeks after the destruction of infectious agents. The disappearance of these immunoglobulins means a cure for the infection. If, after the end of the disease, the presence of IgA antibodies in the blood is determined, then the disease has passed into the chronic stage.

Preparation for analysis

Human blood is most often used to conduct an ELISA blood test. But you can also examine the contents of the vitreous body, cerebrospinal fluid, amniotic fluid.

A blood sample for research is taken from the patient from the cubital vein. It is recommended to donate blood on an empty stomach (at least 12 hours should pass from the moment of the last meal). It is necessary to tell the doctor if the patient is taking medications, as some of them can change the result of the analysis. The reliability of the results of the study is affected by the use of alcohol and drugs.

Decryption

The result form of this analysis indicates a positive (+) or negative (-) result for each class of immunoglobulins.

Consider the interpretation of a possible decoding of the ELISA blood test.

Negative result of IgM, IgG, IgA - lack of immunity to infection.
Negative IgM, IgA and positive IgG result - post-infection or post-vaccination immunity.
Negative or positive IgG, IgA and positive IgM is an acute infection.
A positive result of IgM, IgG, IgA is an exacerbation of a chronic infectious disease.
A negative IgM result and a negative or positive IgG, IgA result is a chronic infection.
Negative IgM result and no IgG, IgA - recovery.

Advantages of the method

An ELISA blood test has many advantages. The main ones can be distinguished:

relatively high accuracy (sensitivity);
the possibility of early diagnosis;
the ability to track the dynamics of the infectious process;
a high level of unification, which allows for mass surveys;
a short period of time required to obtain the result of the analysis;
convenience in work;
automation of all stages of analysis;
relatively low cost.

Flaws

The disadvantage of the ELISA method is that it sometimes gives false negative or false positive results. In addition to technical errors during the study, the cause of false results may be the rheumatoid factor in the patient, the presence of chronic diseases (in which antibodies are produced), metabolic disorders, and taking certain medications.

ascariasis;
trichinosis - the analysis is carried out several times, the maximum level of antibodies is determined at 4-12 weeks after infection;
cysticercosis;
taeniasis;
fascioliasis - antibodies are determined in the acute stage of the disease;
opisthorchiasis - carry out differential diagnosis between chronic and acute forms of the disease;
giardiasis;
visceral and cutaneous leishmaniasis;
amoebiasis;
toxoplasmosis.

4.2 4.20 out of 5 (5 Votes)

Laboratory tests help doctors not only identify the disease, but also determine the body's ability to resist infections. In addition, some allow you to set the stage of pathology. An example of such a study is ELISA, which is often used in diagnostics.

ELISA method - what is it?

Enzyme-linked immunosorbent assay (ELISA) is a laboratory study aimed at identifying specific antibodies of a protein nature to certain antigens in a blood sample. Of paramount importance among many antibodies are immunoglobulins, which are able to exist as part of immunocomplexes. They are synthesized in the body as a result of neurohumoral reactions of the immune system after the introduction of a pathogenic agent into the body.

For each type of pathogenic cells, their own antibodies are produced - as a response. Their detailed diagnostics and analysis help to determine directly the type of pathology that may be present in the human body without manifesting itself. Enzyme-linked immunosorbent assay reveals latent, sluggish pathological processes, determines their stage.

What does the ELISA analysis show?

Having dealt with what is meant by the term ELISA analysis, what it is, it is necessary to note the main diagnostic value of the study. This method is used to determine the presence in a blood sample of the antigens of the infectious agent and antibodies, which are the result of the activation of the immune system. Among the important classes of antibodies, it is necessary to distinguish IgA, IgM, IgG.

An enzyme-linked immunosorbent assay is prescribed if differential diagnosis is necessary, a final diagnosis is made. It helps doctors to identify hidden pathologies. In addition, ELISA can also be prescribed to assess the level of the immune response after the day before vaccination. In most cases, an ELISA analysis (what it is, described above) is prescribed if the following types of pathologies are suspected:

hepatitis;
chicken pox;
helminthiases;
rubella;
polio;
herpes;

In addition, ELISA for certain types of immunoglobulins can also be carried out with:

rheumatoid arthritis;
sepsis;
chronic purulent otitis;
pneumonia;
meningitis;
sinusitis;

How is an enzyme immunoassay performed?

Enzyme-linked immunosorbent assay, ELISA, is carried out by examining a sample of blood taken. A small amount of blood serum and purified antigen is placed on the surface of a pre-prepared special tablet. Connecting them, observe the origin of the reaction in a microscope. An antigen and an antibody of the same species form a complex. To diagnose its formation, additional staining is carried out. Based on the intensity of the staining that has occurred, conclusions are drawn regarding the concentration of immunoglobulins in the patient's blood serum sample.

Analysis by ELISA (what it is, you already know) is sensitive even to a small amount of immunoglobulins, has a high specificity. As a result, doctors can use it to accurately differentiate diseases with a similar clinical picture. The analysis procedure itself does not last long, so the result of the study can be found out on the same day. If you need an urgent diagnosis, you can get an answer after 2-3 hours from the moment of blood sampling.

ELISA blood test - preparation

The enzyme immunoassay method requires some preparation from the patient before it is carried out. Venous blood serves as the test material. Its fence is carried out exclusively in the morning, on an empty stomach. Before undergoing the procedure, the patient is required to avoid emotional overload, stressful situations, and exclude physical activity. To obtain objective results of the study, before taking an ELISA test for chlamydia and other infections, you must:

A day before the analysis, fatty foods, smoked meats and alcohol are excluded from the diet.
Do not smoke before the study.
The last meal should occur on the eve of the analysis with an interval of at least 8 hours before the expected time of the study.

Enzyme immunoassay - material sampling

Analysis by ELISA involves the collection of venous blood as a biomaterial for research. The procedure is carried out in a laboratory. A blood sample of 5–10 ml is taken from the cubital vein using a disposable syringe. Often, special vacuum test tubes are used, after connecting the needle to which the blood fills the container on its own. The received sample is marked accordingly and sent for further examination. More often, the result of the study is known the next day.

ELISA blood test - transcript

The decoding of the ELISA analysis is carried out exclusively by a specialist. This takes into account the results of other studies conducted the day before. It should be noted that the ELISA has two modifications - qualitative and quantitative assessment. A positive result of a qualitative assessment of ELISA indicates the presence in the body of antibodies to a certain type of pathogen. In the future, a quantitative assessment is assigned, which is aimed at establishing the degree of the disease, the stage. With a negative analysis, they speak of the absence of pathogens in the baby's body.

ELISA analysis is negative

A negative test result does not always indicate the absence of pathology. So, an ELISA test for syphilis can be negative in remission, when the pathogen in the body is in low concentration after a course of therapy. Given this option, doctors conduct an additional study after some time. In addition, a negative result can also be observed after a recent infection, when antibodies have not yet been developed by the body in a diagnostic concentration.

Blood test ELISA positive

With a positive result of the analysis, the titer of antibodies, their class, is determined. In most cases, for the diagnosis of infectious processes, the concentration of IgG and IgM is determined. They form at different times.

When an analysis is prescribed, take an ELISA test for syphilis. Methods of laboratory diagnostics. Analysis results - how to determine the norm and deviations. The cost of enzyme immunoassay.

As a rule, constantly when contacting the clinic, doctors prescribe various tests. This allows them to identify infections and diseases that a person suffers from. ELISA, or the so-called enzyme immunoassay, is an excellent way to assess the body's immune system, and to identify infection and stage of the disease by the presence of antibodies.

So, who is assigned to take this analysis and what is an enzyme immunoassay? Doctors prescribe this analysis if a person has the following diseases:

Rash on the body - allergic reactions.
Viruses - herpes, cytomegalavirus.
Sexually transmitted diseases - syphilis, Trichomonas.
Pathology associated with cancer.
Neurosyphilis.

In addition to these diseases, the analysis is prescribed to determine the level of the hormone in the blood. Based on the results, the quality of therapy is assessed. What is syphilis probably every person knows, but does not represent its scale, and how many infected people walk next to us.

Currently, syphilis is the most common disease. This is a treponoma that affects the human body. And as a result, all the internal organs of the patient are affected.

This is a very dangerous infection, and it often happens that it may not manifest itself for a long time. Therefore, a person can be a carrier and distributor for a long time without knowing that he is sick.

Method of laboratory diagnostics

Medicine does not stand still, modern analyzes have become significantly different from the old methods of studying the body. Although they performed their role perfectly, sometimes they had to wait weeks and months for results. This naturally was not favorable for the infected person. What is the expectation of the result, the sick person went through.

Classical analyzes - the detection of syphilis by the Wasserman method, the Kahn method began to lose their positions and were replaced by such tests as ELISA.

This is the most modern method for detecting infection in humans. The result is decrypted using a computer. This allows you to more accurately determine a positive result or a negative test.

During the decoding, a search for antibodies to specific diseases is performed. And as a result of the analysis, it was possible to detect infection when the result was positive. Using ELISA to detect syphilis implies a three-class use of immunoglobulins:

G, M, A - for diagnosis are the most important.
They are produced in an infected person strictly in a certain sequence.
Quickly determine the stage of infection.

ELISA results - normal and positive analysis

If he talks about the analysis of ELISA for syphilis, then in this case it is difficult to say that there is a norm or a deviation. The result is usually either negative or positive. In addition, there are titers that determine the amount of antibodies in the blood.

There are many subtleties in deciphering the analysis, if it showed a positive result, the analysis will still have to be retaken several times to exclude the method of a false positive reaction.

As already written, there are a lot of subtleties when deciphering the analysis, and only the attending physician can determine the result. We give examples in the table, which results can be shown for enzyme immunoassay:

Do not despair if the analysis showed a positive result. As a rule, additional tests and tests are carried out, in various ways, to more accurately establish the diagnosis.

The cost of enzyme immunoassay

As a rule, the cost of this analysis directly depends on the analysis itself and the identification of a specific infection. Determination of markers for infection of various types costs from 200 to 350 rubles. And such an analysis is carried out within two days.

ELISA is the most popular and modern method for diagnosing an organism. The method has shown its effectiveness in detecting infection, and determining the exact period of infection.

Given the pricing policy, we can say that the analysis is available to every person with any budget. It allows the attending physician to get a complete picture of a person's infection. He showed himself in the case and did not disappoint the doctors. At the same time, having received an analysis, the attending physician could respond promptly, prescribing timely treatment.