Decoding the analysis using the Ifa method. What is an enzyme immunoassay? When will the analysis be ready?

With the progress of modern medicine, it is possible to carry out more in-depth diagnostics if certain pathologies are suspected in a patient. One of the informative methods of laboratory research is ELISA analysis, which is carried out by collecting venous blood. That is, nothing generally changes for the patient. But the laboratory assistant-ELISA analyzer carries out a complex technique for examining the collected biomaterial. We will understand what ELISA tests are and what are the subtleties of using the ELISA method as a diagnostic method in the material below.

What is an enzyme immunoassay?

The production of antibodies is provoked by the antigens themselves that have penetrated the human body. When entering the “battle” for the health of the body, antibodies seem to mark antigens, which is what the laboratory technician sees when examining blood. That is, in the collected biomaterial, it is possible to track not only the presence of infection, but also its traces after the body has fully recovered.

Thus, by prescribing an enzyme-linked immunosorbent test for a patient, the attending physician can track the duration of the infection, the degree of its progression, or identify the presence of immunity to a particular infection.

The ELISA diagnostic process looks like this:

• The collected venous blood is converted into blood serum in the laboratory;
• Then the laboratory technician uses a special tray with cells, each of which already contains all the necessary antigens. It is enough to simply drop blood serum into each cell and monitor the reaction of immunoglobulins (antibodies) to antigens. The presence of the “desired” reaction is indicated by a change in the color of the material being tested. Subsequently, the laboratory assistant studies the optical density of the medium under study.

• Ascariasis and enterobiasis (roundworms and pinworms);
• Trichinosis;
• Opisthorchiasis in acute and chronic forms;
• Giardiasis;
• Amoebiosis;
• Toxoplasmosis;
• Leishmaniasis in any form.

Important: enzyme immunoassay can be both qualitative and quantitative. In the first case, the laboratory assistant only confirms or denies the presence of the desired substance in the blood. In the second case, the result of the analysis indicates its concentration in the patient’s body.

Disadvantages of the method

With all the advantages of this diagnostic method, it is worth understanding that an enzyme-linked immunosorbent blood test is not a way to find the cause of a patient’s illness, but only a method of confirming the diagnosis proposed by the attending physician. And since the research is quite expensive, it must be used wisely. In this case, the results of the study should be interpreted only by a qualified specialist.

Decoding the results

After we have sorted out the abbreviation ELISA and what it is ─ found out, it’s worth moving on to interpreting the results. It is important to understand here that if the analysis was carried out qualitatively, the result will only be positive or negative. That is, the diagnosis either confirms the doctor’s suspicions regarding a certain diagnosis or refutes them. In this case, the form will contain the symbols “+” or “-”, respectively.

Important: a negative test result does not always indicate the absence of infection. The fact is that antibodies to antigens can form within 14 days after infection and it is likely that they have not yet been formed.

If a quantitative analysis is carried out, then the type of antibodies, their quantity and stage of activity are determined. In particular, during this diagnosis, antibodies (immunoglobulins) IgG and IgM are determined, which are formed during different periods of infection progression. The most common results in this case are:

• Increased IgM and complete absence of IgG. This picture indicates a recent infection and the acute phase of the pathology.
• Increased activity of both types of immunoglobulins (IgM and IgG). It speaks of a long-standing and chronic course of the infectious process.
• IgG activity and complete absence of IgM. The infection occurred at least six months ago and now the virus is in a protracted chronic stage.
• Lack of IgG and IgA antibodies. The result is undetermined.
• Absence of IgM, IgA and IgG antibodies. Indicates a lack of immunity to a certain infection.
• The activity of IgG, IgM and IgA antibodies indicates an exacerbation of the chronic process.

In addition to identifying the types of antibodies, the laboratory assistant also indicates their quantity in a special column of the form in relation to the blood volume. Remember, once you understand what the ELISA method is, do not interpret the results yourself. The results obtained can only be interpreted with accuracy by the attending physician, depending on the expected diagnosis based on the patient’s clinical picture.

From time to time, doctors prescribe ELISA tests; not everyone knows what this is. ELISA has the following decoding - enzyme immunoassay of blood. Such a blood test helps to understand how the body fights infectious diseases and demonstrates the phase of the disease. Enzyme immunoassay helps in assessing the protective activity of the blood, identifying immunodeficiency in pathologies associated with infections, hormonal problems, etc.

The ELISA blood test works with material that is taken from a vein. In addition, the contents of the vitreous body, fluid from the spinal cord, and smears from the urethra or cervical canal are available for examination. For enzyme immunoassay ELISA, the fluid that surrounds the fetus can be taken from pregnant women.

In this case, blood can be directly tested for ELISA using different techniques. There is direct, indirect, competition and blocking. When the body is infected with some pathogenic agent, which is called an antigen, the immune system begins to produce specific antibodies, for example, to hepatitis. These antibodies are aimed at “dealing” with foreign agents. What are antibodies? These are special proteins that can interact with antigens and form immunological complexes called antigen-antibody. It is for the detection of these complexes that ELISA diagnostics is responsible. To detect an antigen, antibodies are added to the resulting blood sample or the reverse procedure is performed.

A positive ELISA result is based on the reaction of the immune system and enzymes. Under the influence of the first, infectious agents and cellular elements bind, the second helps to visualize the result of the first. The immune reaction involves an antibody and antigen combination. As a result of this process, an immune complex is formed. All cells have antigen on their surface. The immune cell captures the suspicious one, and the antigen, which is fixed on the surface, undergoes a comparison procedure with information that is “loaded” into memory. If there is a match in the description, then the cell returns home, but if not, then a connection occurs, the creation of which is responsible for the antibody that attaches to the surface.

The enzymatic reaction, meanwhile, allows substances to be transformed into new ones. The material is exposed to an enzyme. In this case, the enzymatic difference is ensured by different substrates. The product resulting from this reaction is sent for determination of the amount of pathogen, the determination of which is based on the density of the solution color.

Features of the method

An enzyme immunoassay blood test is prescribed when it is necessary to diagnose allergies and diseases of viral origin. There is also an ELISA test for syphilis and a number of other infections that are transmitted through unprotected sexual contact. This diagnosis is becoming increasingly popular compared to PCR. The fact is that PCR involves working with smears. Unlike PCR, ELISA results can be obtained from blood tests.

In addition, a blood test using the ELISA method can be prescribed when it is necessary to establish the presence of immunodeficiency, diagnose oncology, assess how effective treatment is, determine hormonal levels and undergo a preoperative examination as a whole.

If you compare ELISA studies, for example, with PCR, you can find a number of advantages. The main thing is the possibility of complete diagnosis even at the earliest stages of development. In addition, ELISA results help in determining the specific stage of the disease and the level of its development.

The ELISA test has a higher efficiency compared to PCR; in addition, it can be taken during pregnancy to detect STDs. Anyone who has taken this test can find out the concentration of TSH in the blood serum. This is very important to check what the reaction of the thyroid gland is, whether there are any malfunctions in its functioning.

Additional advantages, however, the polymerase chain reaction also has, is the speed of the study, which means quick results. Doctors also appreciate the accuracy of the results. If we are talking about STDs, then the level reaches 98 percent, as is the case with the TSH concentration.

Of course, there are some drawbacks. However, in this case we are talking about indirect features of the test. In particular, we are talking about the fact that it is impossible to exclude possible errors in determining standards. Sometimes a test taken by an absolutely healthy girl can show a false positive result, or a negative result in the opposite case. However, the classification of psychological research methods in most cases associates such shortcomings with improper preparation or violation of the technique with which the material was collected.

Execution Features

For ELISA analysis, in most cases, blood is donated. Before donating blood, it is important to fast for at least eight hours and avoid taking a number of medications that affect the test result. We are talking about antihistamines and hormonal drugs that affect the functioning of the thyroid gland. In addition, alcohol should be excluded for at least 24 hours. Ensure that you do not smoke at least one hour before donating blood. Distortion of the result is also possible when taking narcotic substances.

Before moving on to the transcript, it is worth mentioning what measurement methods are used for such a test. The test result will indicate antibodies or immunoglobulins Ig. They mean the very specific proteins that were discussed earlier. B-lymphocytes are responsible for their production as soon as viruses, bacteria or fungi enter the body. There are five types of immunoglobulins, designated by the Latin alphabet.

Their differences are associated with different molecular shapes and masses. They have different half-lives and are involved or not involved in infectious processes in different ways. The time frame within which they can be detected from the moment the infection occurs also varies.

If you classify immunoglobulins using molecular weight as a basis, then IgM has the highest indicators. A feature of this type of immunoglobulins is the inability to pass through the placental barrier. If IgM is detected in the test in a newborn child, we are talking about the presence of infection in the fetus.

The vast majority of human blood contains IgG immunoglobulins, the least of which is IgE. Speaking about work within the framework of infectious processes, special attention should be paid to options A, M, G. IgE acts as a marker of an allergic reaction. IgD is found only in the tissues of the lymph nodes and tonsils. This is important from the point of view of creating local immunity.

In addition, the analysis determines antigens. They are understood as substances of high molecular weight, which are known for their organic origin. In particular, we are talking about pathogens of infectious and other spectrum diseases. In addition, we also mean substances that signal various cell changes that are inevitable in a number of diseases. An immune complex is also indicated, which demonstrates an antigen-antibody complex that takes part in the immune process.

Typically, production times depend on the specific laboratory you contacted. Some laboratories are able to provide results within a day or two, others take a week. Delays may be due to the need to accumulate a certain amount of serum.

Impact on results and interpretation

Despite the fact that ELISA is considered one of the most accurate testing methods, errors still occur. The procedure for taking the material, improper transportation and storage of the material can affect the correctness of the results. Taking medications, as mentioned above, the presence of hidden diseases. Metabolic disorders or immunodeficiency will also not allow you to obtain the correct indicators. During the period of life up to one year, newborns may also have inaccurate indicators. This is due to the fact that maternal antibodies are present in the body.

Speaking of decoding, the analysis forms use a positive or negative sign to indicate the calculation results for each of the immunoglobulin classes. The following are likely options.

The absence of detected IgG, IgA and IgM indicates complete recovery. A negative result for components such as IgM, IgA, IgG means a lack of immunity to infection.

The combination of a positive and negative result for IgG, IgA in combination with positive IgM indicates the presence of an acute infection in the body. A positive IgG result combined with negative indicators for IgA and IgM corresponds to the post-vaccination period or the acquisition of immunity as a result of an infection.

The combination of a positive or negative result for IgG, IgA and a negative result for IgM indicates the presence of an infection in its chronic course. A positive result for three components: IgG, IgM, IgA indicates an exacerbation of an infection that was in a chronic form. In addition to directly clarifying the antibody classes, as part of deciphering the ELISA analysis, the doctor receives information about their quantitative indicators. It is important to emphasize that the attending physician should be responsible for decoding. The fact is that the combination of some components may lead him to think about the obtained false result, which will lead to retaking the test. Independent decryption in this case is useless.

How is an ELISA study carried out?

Reaction mechanism

The enzyme-linked immunosorbent assay is based on the immune reaction of an antigen with an antibody, and the attachment of an enzyme tag to antibodies allows the result of the antigen-antibody reaction to be taken into account by the appearance of enzymatic activity or by a change in its level. In a simplified form, the reaction mechanism can be presented as follows:

Calculation of results

Carrying out enzyme immunoassay

For serodiagnosis, 96-well polystyrene plates are used, on the walls of the cells of which the antigen is pre-adsorbed. The test serum is added to the cell of the tablet. In this case, antibodies homologous to the antigen are attached to it. Unattached antibodies are removed by washing. Next, antibodies against human immunoglobulins (antibodies) labeled with an enzyme are added to the cells. If detectable antibodies were present in the test serum, then at this stage they will act as antigens with which the labeled antibodies will react. The addition of a chromogenic substance (dye) after washing will allow us to take into account the reaction of the developing color in the cells. The intensity of the color is proportional to the amount of enzyme, and therefore the amount of antibodies. When measuring the optical density (OD) of a liquid in a cell and comparing it with a control sample, the concentration of antibodies is calculated in units of volume. The most often used is to calculate the results in units of optical density. It must be taken into account that Each test system has its own indicators for recording the results and indicators of normality and pathology that should be guided by when interpreting the results.

What infections can be detected by ELISA?

Mainly in modern venereology it is used for the diagnosis of syphilis (in combination with other reactions), HIV infection, viral hepatitis. It has limited value for the diagnosis of chlamydial infection, cytomegalovirus infection and other herpetic infections. The ELISA method is also used to determine antibodies in various infectious diseases , levels of hormones, autoantibodies and various markers of cancer.

How to interpret ELISA results

Studying the presence and level of antibodies of various classes in some cases helps determine the stages of the infectious process

Unfortunately, such an important advantage of ELISA as the quantitative determination of antibodies is not of great importance in practical work - i.e. does not allow an accurate diagnosis and does not affect the dosage and timing of medications.

What is the role of the ELISA method in the diagnosis of syphilis

The ELISA method in the diagnosis of syphilis was first used in 1975. Currently, it is widely used for the serological diagnosis of syphilis in Russia and is used as a confirmatory test for syphilis. A study is usually carried out that identifies the so-called total antibodies to Treponema pallidum antigens (IgM and IgG) , although in some cases it is possible to determine only “early” antibodies of the M class. ELISA for syphilis becomes positive after 3 weeks from the moment of infection and remains positive for quite a long time even after treatment (sometimes for life). Therefore, as a test confirming the cure of syphilis, ELISA is not used. In most cases, only a qualitative determination of ELISA is carried out - i.e. only a positive or negative result, although quantitative determination is also possible.

Linked immunosorbent assay(or ELISA for short) is a laboratory test that helps make an accurate diagnosis, identify hidden diseases, determine predisposition to certain diseases, and also monitor the effectiveness of prescribed therapy. During the study, antigens characteristic of specific pathogens and antibodies to them are detected in the patient’s blood serum.

What's the point

In order to understand the principle of ELISA, it is necessary to remember how the body’s immune system works, what “antigen” and “antibodies” are, and what functions they perform.

An antigen is a molecule that carries certain information about a cell. If a foreign antigen enters the body, antibodies (or immunoglobulins (Ig), in response to the appearance of a foreign microorganism in the body, bind to it and recognize whether it is one’s own or a foreign one. When receiving a “foreign” signal, the antibodies begin to destroy the potentially dangerous object. This “antigen” interaction -antibody" is called immune complex. The ELISA method is based on it.

Indications

The analysis is widely used to diagnose various types of diseases. And what is especially valuable is that this study quite accurately diagnoses diseases that occur in the body latently, without symptoms.

With its help you can identify:

• sexually transmitted infectious diseases (chlamydia, ureaplasmosis, mycoplasmosis, syphilis, herpes, HIV, etc.);
• toxoplasmosis, tuberculosis, hepatitis, measles, etc.;
• autoimmune problems;
• oncology;
• sex hormones;
• thyroid hormones;
• allergies.

ELISA can even detect markers of heart disease. In addition, it is prescribed to evaluate the effectiveness of the course of treatment, as well as before certain types of surgical interventions.

Preparation

Blood for research is taken from a vein on an empty stomach, preferably in the morning.

The day before you should refrain from alcohol, sugary drinks, coffee and a large dinner. In addition, the results of the indicators may be affected by the use of certain medications, so consultation with your doctor is necessary.

Smoking should be avoided 4 hours before the procedure.

Enzyme immunoassay blood test at ON CLINIC

The international medical center ON CLINIC is equipped with its own laboratory, which has an international quality control certificate. Here, experienced and qualified specialists conduct various types of analyzes (more than 1000 items).

Among the advantages of this method, one can highlight the fact that it detects it already at the earliest stages of the development of the disease. The sensitivity of the test is 90%. The study accurately shows the dynamics of the infectious process, which allows the specialist to monitor the effectiveness of therapy. The entire process is fully automated, which eliminates the influence of the so-called “human factor”.

In addition, high-precision equipment allows you to obtain reliable research results in a minimally short period of time.

You can decipher the results on the same day with your doctor. Based on them, the doctor will choose a treatment tactic that is right for you.

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