A blood test using the ELISA method
Among the methods of blood analysis( a reference to the third article in this file), allowing to assess the ability of the body to resist infectious diseases and showing the phase of the disease, an important place is taken by enzyme immunoassay( ELISA).Carrying out of this research allows to comprehensively assess the activity of the protective function of blood and to reveal the state of immunodeficiency in infectious pathologies, as well as blood diseases, autoimmune processes, hormonal problems.
How does it manage to capture as many targets in one analysis, and what are the indications for it?Let's try to understand.Table of contents: What is an ELISA test? What are immunoglobulins? Indications for the appointment of an enzyme immunoassay. How is an ELISA performed? Blood plasma immunoassay Benefits Are there deficiencies in an ELISA blood test?Immunoenzyme analysis of blood in parasitology
What is a blood test performed by the ELISA technique
This is a laboratory test that allows to determine the presence of specific antibodies( protective factors of the blood of the protein nature) to certain antigens( pathogens).Among antibodies, immunoglobulins, which can exist as immunocomplexes, are of paramount importance.
Immunoglobulins are produced due to complex neurohumoral reactions of human immunity, arising as a response to the introduction of foreign antigens.For each type of pathogen agent, specific antibodies are produced.They act by "binding" the antigen or pathological microorganism, form a complex compound "antigen-antibody" with subsequent neutralization, enzymatic lysis, phagocytosis reactions and withdrawal from the body.
Note: is determined by the presence of certain complexes by the ELISA method, the type of pathogen or the harmful substance present in the patient is determined.
You can learn the basic principles of the functioning of human immunity by watching this video review:
What are the immunoglobulins
5 main classes of immunoglobulins - IgA, IgM, IgG, IgD, IgE have been discovered and studied.The role of the rest is not yet fully understood and it is in the stage of scientific research.
Note: the most important in practical medicine is the importance of immunoglobulins classes - A, M and G. Informative definition is based on different time intervals of their appearance, maximum and disappearance.
Consider this issue in more detail.
The main objective of immunoglobulin A( IgA) is to protect the mucous membranes of the respiratory tract, gastrointestinal tract and urinary system.With acute onset of the disease, they can not be identified.These protective complexes appear only from 2 weeks of onset of the disease, sometimes later.The bulk of immunoglobulin A is concentrated in the mucous tissues.Approximately 80%.The remaining antibodies circulate in the blood.The main function is to neutralize and destroy microorganisms.After the acute manifestations of the disease abate, the number of these immunoglobulins begins to decrease and completely disappears at the term of up to 8 weeks after the onset of the disease.If IgA are detected at a later date, this indicates a chronic process.
The main and the first markers of the acute phase of developing pathology are immunoglobulins of class M( IgM) .They are found to 5 days of the onset of malaise.Determine their presence in the blood can be about 6 weeks.Then they begin to disappear quickly.
Residual immune response characterizes the presence in the blood of immunoglobulins class G( IgG) .The appearance of these factors in the blood is detected about a month after the onset of the disease.In the future, they can be determined for many months, years and even a lifetime, performing a protective function from the return( relapse) of the disease, and in some cases making it impossible for the secondary development of pathology.If the amount of immunoglobulin G begins to grow again, then you can suspect a second infection.A similar conclusion can be drawn by conducting two or three samples taken at intervals of 2 weeks.
Immunoglobulin E( IgE) is used in the practice of parasitology.
Immunoglobulin D( IgD) is located on B-lymphocytes, is in a small concentration in healthy people.After 10 years of life reaches the maximum values.The amount of immunoglobulin D increases during pregnancy, in patients with systemic connective tissue diseases, bronchial asthma, diseases caused by immunodeficiency.
Indications for the appointment of an enzyme immunoassay
Determination of antibodies to the presence in the body of pathogens causing:
- ureaplasmosis and mycoplasmosis.
There is an increase in the number of immunoglobulins in helminthic invasions.
Diagnosis is performed to detect:
- herpetic diseases;
- group of viral hepatitis;
- of the Epstein-Barr virus;
- of cytomegalovirus.
With the help of ELISA it is possible to detect the presence of antibodies to 600 species of allergens, to detect the state of immunodeficiency, to conduct a comprehensive examination before transplant operations, to conduct a comprehensive analysis for the effectiveness of treatment.
ELISA is an additional method of detecting cancer cells.
How is the blood IFA performed?
For the enzyme immunoassay, in most cases, the patient's blood is used, sometimes the vitreous tissue, spinal fluid, amniotic fluid are taken.
Blood is injected through the injection needle into the syringe from the ulnar vein.The study is performed on an empty stomach.It should be remembered that taking certain medications can affect the result of the analysis.Before donating blood should refrain from smoking, drinking alcohol.Distort the results can the use of drugs.
In the case of negative values of immunoglobulins IgM, IgG, IgA, one can speak about the absence of disease or its initial phase, and the result with minuses is possible with full recovery after a considerable amount of time.
If IgA and IgM are not detected, and IgG is shown positively, then in all probability it is a question of the formed immunity after an infectious disease, or after vaccination.
In the case of a high IgM titer with negative values of IgG, IgA, it can be concluded that there is an acute infectious disease.
Simultaneous positive values of the results of immunoglobulins - IgA, IgM, IgG are characteristic for the acute phase of the recurrence of the existing chronic disease.
For chronic infection, in the phase of remission, the ELISA shows negative immunoglobulin M( IgM) values, with the result of the immunoglobulin G( IgG) and A( IgA) being positive.
Advantages of the method of enzyme immunoassay
The main advantages of the ELISA method are:
- low cost of analysis;
- diagnostic specificity, accuracy;
- dynamic control( repeat analysis to determine the effectiveness of treatment and stages of the disease);
- the possibility of conducting mass surveys in the foci of infection;
- speed of obtaining the result;
- relative ease of analysis;
- the possibility of using information technology in processing;
- safety and painlessness for the patient.
Are there deficiencies in IFA blood?
The main negative point of the study is the possibility of obtaining false-negative and false-positive data.The cause of misunderstandings can be technical shortcomings, medication, which can distort the picture.
Note: falsify the result of the analysis can impair the metabolic processes in the body.Caution in the findings should be observed when several chronic processes are combined in the patient.
Immunoenzyme analysis of blood in parasitology
The possibility of using ELISA in the diagnosis of parasitic diseases is determined by specific immunoglobulin E( IgE), which tends to increase precisely for this group of diseases.In addition, immunoglobulin E is a marker of atopic reactions associated with allergic processes.In the blood, it is in small quantities.Its main localization is mucous membranes, basophils, and marcophagi.The main function of this protein complex is to protect the mucous membranes of the body.But at the same time he is a participant in immune reactions directed against parasites.Activation of IgE is controlled by eosinophils and macrophages.This is an important fact in comparing the analysis data in establishing the diagnosis of the disease.
ELISA is used to detect:
- of round helminths( ascaris, pinworm);
- acute and chronic form of opisthorchiasis;
- the presence of lamblia( as an additional analysis);
- forms of leishmaniasis;
- content of toxoplasm;
Important: immunoglobulins are produced in the body as antibodies to certain antigens.Therefore, even with the highest specificity of the analysis, errors in accuracy are not excluded.With parasitic diseases, the probability percentage is about 90%.
In conclusion, it should be noted that modern immunology is constantly in the development stage, searching for new methods of diagnosis and treatment of diseases.
Stepanenko Vladimir, Surgeon