Doubtful HIV. Doubtful analysis result: what does the laboratory doubt? How is the incubation period of HIV qualified?

Particular attention is currently being paid to the diagnosis of HIV (immunodeficiency virus) in humans. Detection of the disease at an early stage will help to start the treatment course earlier and this will significantly affect the increase in the life of the patient.

After an HIV test is taken, the interpretation of the results is usually positive or negative. In this case, there is a primary diagnosis and a secondary one. In the primary - a person is checked with the help of ELISA. If necessary, a second blood test for HIV is done. What does positive and negative mean? How is an HIV test decoded? Why does a person who is not a drug addict and alcoholic, has a permanent sexual partner, deciphering the analysis for the immunodeficiency virus gives a positive but doubtful result?

About HIV

The causative agents of the disease are of the 1st and 2nd type. For a long period of time, their presence in a person goes unnoticed, then the immune system is affected first of all, then other human systems.

With the main method of laboratory diagnosis of the immunodeficiency virus, antibodies to HIV are detected. Enzyme-linked immunosorbent assay (ELISA) is the basis of the method, it is sensitive (99.5% and above) and specific (99.8% and above). In addition, when diagnosing HIV using ELISA, the p24 antigen is determined.

Each test system has different indicators, in connection with this, they determine the various protein structures of the viral envelopes. The causative agents of HIV come in two subtypes: 1st and 2nd or HIV-1 and HIV-2. Virus particles look like spherical shape having an outer phospholipid shell. For the 1st subtype, it has the following molecular weight: gp120, gp41, gp160. 2nd subtype contains gp105, gp36, gp140. For the inner envelope of the virus, the molecular weight is also known. For the 1st subtype, these are p55, p17, p24. For the 2nd - p16, p25, p55.

For each test system to detect a virus, there are three main sets of proteins.

In general, the result of an ELISA can be:

negative;
false positive;
false negative;
doubtful or uncertain.

Diagnostic methods detect antigens, antibodies.

About normal result

Norm - what does it mean? When the HIV test is negative, it is considered normal.

1. The latest generation of ELISA test systems allow you to determine the presence of antibodies to HIV and protein particles. If the analysis is normal, then antibodies and protein particles of the pathogen are not found in the blood. But it is possible to say for sure that a person is healthy on the basis of this, if there was no risk of infection for 3 months before the delivery. Otherwise, after some time, you need to repeat the test again.

There were cases when HIV was detected only after 6 months. Therefore, if the result is negative, and there was contact with an HIV-infected patient, for reliability it is necessary to repeat the test after three, four and six months. It happens that the ELISA gave a negative result, and the person clearly has a suspicion of the presence of signs of HIV, it is recommended to take the test again. An erroneous result is possible due to early dates analysis or due to the human factor.

2. If the result is negative on immunoblot, then this is currently the most reliable analysis.

If a person has an immunodeficiency virus, and the result is negative, then most likely this is a medical error that can occur at any stage of the test. If the result is negative when repeating the immunoblot after three and six months, then there is nothing to worry about, this indicates the norm. And only after a negative response of the immunoblot will a certificate be issued that the HIV test is negative.

3. PCR research in adults in diagnosing the immunodeficiency virus is used extremely rarely, and this method is used for newly born children.

A negative result is also considered the norm here.

4. According to sociological research, many people use a rapid HIV test. At the sight of a negative line, people calm down and refuse to go to a medical facility, even if they have all the signs of HIV infection. But you need to know that the accuracy of the rapid test is eighty-five percent. In addition, at home, it can be carried out incorrectly, or the conditions for its storage will be violated. There is an even greater chance that the result is incorrect. Even taking mineral alkaline water 8 hours before testing will affect the test result. Therefore, the fact that the human immunodeficiency virus is absent on the basis of a rapid test, even if it is negative, is far from always a true statement.

Deciphering the analysis

After testing has been carried out, people often have the question of how to decipher the result of the research, what to do if a positive result for HIV is obtained.

1. If the ELISA showed the presence of all or almost all antibodies to antigens according to this test system, this means a positive test for HIV. If the response after the second serological enzyme immunoassay is positive, then an immunoblot should be performed. The interpretation of his results will be more correct. If the enzyme-linked immunosorbent assay gave a positive result, the next immunoblot analysis also showed the presence of HIV, then the final result is put. When analyzes are deciphered, you need to know that a positive HIV test is determined by:

60% to 65% 28 days after infection;
in 80% - after 42 days;
in 90% - after 56 days;
in 95% - after 84 days.

If the response to HIV is positive, this will mean that antibodies to the virus have been detected. To avoid a false positive answer, it is necessary to re-test, preferably twice. If antibodies to immunodeficiency are detected when passing two tests out of two or when passing 3 tests in 2 of them, then it is considered that the result is positive.

The p24 antigen can be detected in the blood as early as 14 days from the date of infection. Using the enzyme immunoassay method, this antigen is detected from 14 to 56 days. After 60 days, it is no longer in the blood. Only when AIDS is formed in the body does the re-growth of this p24 protein in the blood occur. Therefore, enzyme immunoassay test systems are used to detect HIV in the first days of infection or to determine how the disease progresses and monitor the treatment process. The high analytical sensitivity of enzyme immunoassay detects the p24 antigen in biological material when HIV first subtype at a concentration of 5 to 10 pg / ml, with HIV of the second subtype from 0.5 ng / ml or less.

2. A questionable result of an enzyme immunoassay means that when diagnosing, they made a mistake somewhere, as a rule, medical workers mixed up something, or the person has signs of infection, and the result is negative, which causes suspicion, the person is sent for re-testing.

3. A false positive result is understood as a result when blood tests were taken under the following conditions of the patient:

pregnancy;
if a person has a hormonal imbalance;
with prolonged immunosuppression.

How to decipher the analysis in this case? A false positive result is given if at least one protein is detected.

Due to the fact that the p24 antigen is very dependent on individual variations, using this method, 20% to 30% of patients are detected in the first period of infection.

About the indicators after the study by the method of polymerase chain reaction

Using this method, HIV RNA and DNA are detected almost immediately after infection. But the final diagnosis is not made, mandatory confirmation by other methods is required. "Help decipher the PCR result." - quite often you can hear such a request. What is written in this case if an immunodeficiency virus is detected? When answering the result of an analysis made using PCR, the number of RNA copies per milliliter of blood is indicated. The table below shows the result depending on the quantitative characteristics in the blood.

It is good to use the above table when testing for AIDS is done, since it is easy to determine the stage of the disease from it.

These tables, taking into account various test systems, are available in laboratory rooms for each method of enzyme immunoassay and immunoblotting.

Often asked: "Decipher the answer after the study by the polymerase chain reaction in terms of CD4." The normal number of CD4 cells is from 600 to 1900 cells per milliliter of biological material. This corresponds to HIV-negative status. But you need to know that these indicators, even in healthy people, are not in this range.

IN modern world many laboratories already have good equipment with which you can fully examine the body for the content of HIV infection in it.

In contact with

The problem of AIDS and HIV today has become very relevant, and all over the world. About how many people (almost half a million) die annually from acquired immunodeficiency syndrome, doctors know firsthand. AIDS and HIV are two different diagnoses. AIDS (acquired immunodeficiency syndrome) is already a progressive disease that becomes fatal for many infected, HIV is just a virus that allows people to live with it for a very long time and be carriers of the disease.

talking in simple words, with acquired immunodeficiency syndrome, immunity is completely absent - antibodies that fight infection, viruses and bacteria that enter the bloodstream. A person diagnosed with AIDS can die from the most harmless common cold. HIV and AIDS are not transmitted by rodents, insect bites or personal hygiene items. The main link for infection is blood and semen. The only way to make sure that antigens are present is to donate blood anonymously for AIDS and HIV. Moreover, you can pass the analysis at will - anonymously or without hiding your data.

After the transcript is carried out and the results are known, it will be possible to find out whether the result is positive or not. Even if the person is not promiscuous or anti-social (does not use drugs or alcohol), the score and result may be positive but questionable.

Before taking an anonymous HIV test, it is necessary to take a clinical blood test and then draw a conclusion whether it is doubtful or not. That is, it is possible to determine the immunodeficiency virus - negative or HIV-positive, only after donating blood anonymously. After the decoding is done and the results are processed, it will be possible to draw any conclusions.

Antibody values for a false positive HIV result (anonymous) will be higher than normal. But according to one indicator, it is impossible to say that a person has a virus. In 50% of cases, indicators can be overestimated for completely different reasons.

Many people are interested in the question - how long does it take to get the results and what is the expiration date of the analysis. It doesn't matter if the analysis is anonymous or open, its validity period is 5-6 months. And the question of how long to wait for the result can be answered unambiguously - 2-3 weeks.

HIV diagnosis is carried out in several stages:

carrying out enzyme immunoassay (ELISA);
immunoblotting technique.

ELISA clinical blood test for HIV is carried out in order to identify the total spectrum of antibodies against the antigens of the immunodeficiency virus. This is a screening method. It detects suspicious antibodies and weeds out healthy ones. But doing this blood test is not enough. It is at this stage that false positive results occur.

Immunoblotting is a more detailed blood test for HIV. It confirms the fact of infection. Its essence is the destruction of the virus into antigens (ionized amino acid residues that have a different charge). Using electrophoresis (isolation of plasma and red blood cells from the blood) and further examining the serum, doctors determine if antibodies are present that interact with the immunodeficiency virus. This method is much more efficient, but it cannot be guaranteed.

False-positive results for the immunodeficiency virus are quite common, literally shocking the person donating blood. The thing is that there are a lot of diseases that can provoke a false positive result.

It should be noted that ELISA for AIDS can only be called preliminary testing for the immunodeficiency virus and it is not necessary to rely on its description at all. In most cases, it is offered to pass it for the overall clinical picture. Only after the second stage of testing can you anonymously verify whether the blood result is doubtful for AIDS, HIV or not.

Many people ask how long the study itself takes. It takes 15-20 minutes to draw blood. Only disposable medical devices are used for the study. By the way, it is much easier to get infected with the immunodeficiency virus in a hairdresser or in a movie theater than in a medical laboratory.

Even the most cutting-edge equipment is not always able to detect the presence of antibodies and antigens of HIV infection. And the point is not in the equipment itself, but in the period of reproduction of virus cells in the blood. In some cases, especially after taking ELISA for AIDS and the immunodeficiency virus, people get a false positive result. But this does not mean that a person really has AIDS. To do this, it is necessary to pass repeated tests after a while (the expiration date of the result is valid for about six months). The reasons why the result can become a false positive, whether it is anonymous or not, are violations of the rules for donating blood. Ordinary seeds or previously eaten spicy, sour, fried foods, and even mineral carbonated water, especially alkaline - for example, Borjomi, can provoke a dubious result, no matter how many of them are eaten - a lot or a little.

Only highly qualified medical laboratories can guarantee anonymous and accurate research. But in order to make sure once and for all that there is no AIDS or HIV virus, it is better to repeat the study in six months. This is no longer needed by doctors, but by the people themselves. The window period is present in all people. It is also called the incubation period, and immediately after infection, it is impossible to detect the immunodeficiency virus. No need to stop if the result is positive, it may be a false positive.

How is the incubation period of HIV qualified?

The initial stage of infection with the human immunodeficiency virus in almost 99% does not manifest itself. It depends on the general state of immunity and the body as a whole. It may take a long time until a person already has symptoms confirming the presence of HIV antigens. But on the other hand, a person remains a source of infection for other people. Whether HIV is present can only be determined by taking an ELISA 3-6 months after the actual infection. The window period is a time span. Its beginning is the penetration of the virus into the blood, the end is the detection of the virus. Every person has a different window period. How long is the window period? Approximately 2 to 5-6 months. And from this period depends on how accurate the study will be. It is during this period of time that the results, under the influence of certain factors, can be false positive.

False positive HIV test (anonymous)

The ideal HIV test is 100% accurate in determining whether the virus is present or not. But for a number of reasons, the result may be questionable. Today, anonymous analysis at home is considered very fashionable and common. This provides people with complete confidentiality, but cannot protect against errors. It is at home that test results often become false positives.

In order to dispel doubts, it is better to take an ELISA test in qualified laboratories. In this case, the risk that the result will be questionable is excluded by 99.9%. In addition, home studies can give a result that people do not expect at all, both positive and negative.

Conditions that can cause a false positive result:

cross reactions;
the period of pregnancy (risk group - women who have given birth several times);
the presence of normal ribonucleoproteins;
multiple blood donations;
infectious lesions of the respiratory system;
influenza virus and hepatitis;
recent vaccinations (tetanus, hepatitis B, influenza);
very thick blood;
primary autoimmune liver diseases;
tuberculosis virus;
herpes virus;
poor clotting;
fever;
liver disease caused by alcohol;
arthritis;
violation of immunoregulatory processes;
damage to small vessels of the body;
oncological diseases;
different types of sclerosis;
organ transplant;
elevated bilirubin;
elevated levels of antibodies;
critical days.

Some diseases can cause cross-reactions. For example, due to an allergy in the blood, antigens that are incomprehensible to the body can be produced, which it recognizes as foreign. Such antigens can cause a false positive result.

During pregnancy, a woman experiences hormonal failure, so in some cases there may be a false positive result on the test. At menstrual cycle blood for the immunodeficiency virus is not recommended.

Any infectious, fungal and viral diseases almost always give a positive result for the presence of the immunodeficiency virus. For this reason, doctors advise to undergo treatment for the disease, and only after 25-30 days to undergo an examination.

Diseases, oncology, elevated bilirubin, vaccinations - all these factors affect the result. If a non-standard set of enzymes is present in the blood, then an anonymous analysis will be false positive.

For these reasons, doctors do not tell people that they have already been diagnosed with viral infection immunodeficiency. And having heard that the analysis is positive, a person should first of all think about what could provoke a positive result.

False-positive human immunodeficiency virus tests are very common after organ transplantation, especially during the period when the organ is engrafting. In this case, unknown antibodies are produced, which, when tested, are encoded as antigens of the immunodeficiency virus.

Before taking an anonymous test for HIV or AIDS, it is imperative to notify the doctor about whether the disease is present and how long it lasts. This must be done in order to exclude false positive analysis.

In order not to become a hostage of a false positive analysis

ELISA analysis should be performed after doubtful contact after 6-12 weeks. During this period, human immunodeficiency virus antibodies are detected. In this case, 70% false positive analysis can be excluded.

Before donating blood for HIV (ELISA), you must not break the diet, do not drink alcohol, drugs and do not have sex at least 2-3 weeks before the HIV test. Blood is given only on an empty stomach. How much blood the doctor will take, and how much the test costs, as well as the expiration date of the test, can be found directly at the medical center. With existing viral or infectious diseases, it is better not to take an analysis, you must contact the laboratory 35-40 days after recovery. If you have other chronic diseases, you should inform your doctor.

Even if the analysis turned out to be positive, there is no need to panic, it may be a false positive. How many months should pass after the first delivery?

After 3-4 months, the ELISA analysis can already be retaken. In a person whose blood does not contain the immunodeficiency virus, the result will be guaranteed to be negative.

Many people are interested in the question of how long HIV lives? The human immunodeficiency virus, getting into the air, dies almost instantly. It dies at temperatures above 40°C. Therefore, if it were possible to heat human blood to such a temperature, HIV would be defeated, and as many people would not die as many die from the virus today.

False positive HIV test - medical errors

Very often people become hostages of a false-positive test for HIV, AIDS, not only due to the fact that only an ELISA test was taken, but also because of the mistakes of medical personnel. A false positive result can be caused by:

improper transportation of the collected blood;
the use of low-quality serum for ELISA analysis;
improper storage of collected blood;
in violation of the rules for blood sampling.

By committing negligent actions, incompetent medical staff calls into question social development person's personality. Of course, not all medical centers allow such errors. Basically, even pregnant women go to a regular hospital to donate blood for HIV and AIDS without any fear.

To date, many laboratories are equipped with good equipment that will help to conduct a complete and extended examination for the presence of human immunodeficiency virus in the blood.

January 15th, 2014

Could it be that the antigen is already bound by antibodies, but there are still not enough antibodies for the test?
No, if there is HIV in the body, and if the antibodies were able to bind so much antigen that the AG line of the test ceases to see it, then it will definitely already detect antibodies to HIV, and the test will still be positive.

What generation was my test?
For the Russian Federation - a quarter, we do not import or use others. The name of the test is usually one of: "Combo", "At/Ag", "AT/AG", or "p24".

What is the window period for 4th generation tests (Ag/At Combo)?
4th generation test systems are able to detect not only antibodies to HIV that the body produces in response to an infection, but also directly HIV, by detecting the p24 viral protein. The p24 protein can be determined very early, but its level in the blood in the period after infection gradually decreases, but at the same time as this decrease, the level of antibodies increases. All people are different because it is impossible to name the exact 100% minimum period when there is no reason to doubt the test. However, today there is a sufficient number of studies that give us very definite guidelines, here are just a few of them:

14 days ();

17-18 days (2.5 weeks) ();

3-4 weeks ();

One month ().

So, how long does it take for ELISA of the 4th generation to absolutely reliably exclude HIV?!!!
The 4th generation test can in some cases detect HIV infection as early as a week after infection, but it is still impossible to focus on this, because it is rather an exception. As you saw above, a month is quite a reliable period for modern laboratory test systems.

.
In 950 out of 1000 people, a 3rd generation ELISA test or only a 4th generation AT-line test will detect antibodies to HIV after 4 weeks. The remaining 49 people will develop antibodies at 5, 6, 7, 8 weeks, and definitely after 12 weeks. There remains this 0.1%, which medicine will leave for every rare and casuistic case. But, it is important to note that we have just talked only about antibodies, and 4th generation tests also detect the HIV antigen, it is known that AH in the interval from 1 to 8 weeks will be detected in 95% of those infected, and in the sum of AH and AT, the line of the test system will give better parameters than 95% after 4 weeks or 99.9% by 12 weeks. It cannot be more reliable, this is absolutely enough.

If you think that you had a risky contact, then do an ELISA after 6 weeks after a dangerous contact - the reliability of a negative result will be extremely close to 99.9%. Many experts consider 6 weeks for a 4th generation ELISA in the laboratory to be perfectly sufficient to exclude HIV infection, but even the most conservative guidelines do not consider the feasibility of retesting after 12 weeks. Draw your own conclusions.

At any time from a potentially dangerous situation after 6-12 weeks, ELISA does not increase or lose its reliability, remaining an accurate diagnostic method after a year, and after two years and beyond. In very rare cases, diagnostic problems can occur in very severe, actually terminal patients with a detailed picture of AIDS. You can read more about this, also there are answers to questions about the so-called. late seroconversion.

Serological diagnosis HIV infection involves the detection of virus antigens and antibodies in the blood serum. Detection of antibodies to using ELISA (enzyme-linked immunosorbent assay) is the main method of laboratory diagnosis. All positive results are confirmed by immunoblotting.

based on the detection of antibodies in the blood and biological fluids of the subject. Used in cases where you need to quickly get the result.

Level of immunosuppression determined by the method of counting CD4 and CD8 lymphocytes, followed by determining the ratio of CD4:CD8.

HIV test anonymously

In public health institutions (clinics and hospitals), it is not possible to give an anonymous blood test for HIV. Information about the results of the study will be known to a narrow circle of physicians who are required to keep medical secrets.

Anonymous testing rooms exist on the basis of the AIDS Centers, where each study is assigned a number.

Rice. 4. Blood tubes are sent for serological testing.

HIV test mandatory

There are four populations for which HIV testing is mandatory but not enforced:

Donors of blood and other biological material.
When applying for a job in an institution where an employee may have contact with obviously infected material and patients.
Foreign citizens upon receipt of visas for residence (more than 3 months) on the territory of the Russian Federation.
In the presence of clinical indications to persons in places of deprivation of liberty.

Compulsory testing of the population for HIV is futile and contrary to human rights. Forced testing of the population in the Russian Federation is illegal.

Rice. 5. HIV testing of convicts is carried out according to clinical indications.

How much does an HIV test cost

In public institutions, HIV testing is free, in private clinics - for a fee:

The cost of ELISA is from 400 to 800 rubles. The answer will be ready after one day. There is an urgent diagnosis, when the answer can be received within 2 hours.
The cost of an HIV test using the immunoblot method ranges from 3,000 to 5,000 rubles. The result will be ready in 4 - 7 days.
The cost of an HIV test by PCR is 10-12 thousand rubles. The result will be ready in 10 - 14 days.

How much is an HIV test done

In public institutions, the time frame for obtaining HIV test results is:

When using 3rd generation ELISA, the results give the most reliable result after 12 weeks from the moment of the alleged infection.
When using ELISA 4th generation - 6 weeks.
When using PCR - 4 weeks.

How to get tested for HIV

It is necessary to take an HIV test no earlier than 3-4 weeks after the alleged infection.
Testing is carried out no earlier than 8 hours after a meal.

From the liquid you can use only plain water.

For analysis, 3-5 ml of blood is taken from the cubital vein, for which a conventional syringe or needle with a pump is used.
Before transport to the laboratory, blood serum can be stored in the refrigerator for up to 7 days. Without a refrigerator no more than 30 minutes after collection.
Transportation of test tubes with blood serum is carried out in special thermal containers at a temperature of +4 - +8 o C.

Rice. 6. For analysis, 3-5 ml of blood taken from the cubital vein is taken, for which a conventional syringe or needle with a pump is used.

When taking blood from a vein, the human immunodeficiency virus cannot be infected.

False positive HIV test and other types of test results

The results of an HIV test can be interpreted as positive, negative and questionable.

Doubtful test result obtained in the presence of antibodies in the blood serum that cross-react with the proteins of the human immunodeficiency virus. In this case, the analysis is re-submitted, and during its implementation, more specific test systems will be used. If the questionable result persists, then testing should be carried out every 1 to 3 months for six months.

Positive HIV test result(seropositive) indicates the presence of antibodies to the virus in the blood. In this case, the enzyme-linked immunosorbent assay (ELISA) is repeated and, if a repeat positive result is obtained, is confirmed by an immunoblot test with the same blood sample.

Negative HIV test result(seronegative) indicates the absence of HIV infection, or the infection has occurred quite recently and antibodies have not yet been developed in the blood of the subject (the “window” period). In this case, the examination should be repeated after 3 and 6 months.

False positive HIV test result is recorded when the cause was not the human immunodeficiency virus, but pregnancy, an autoimmune disease, an allergy, any other infectious disease, a recent vaccination, oncopathology, organ transplantation, and even ordinary food (seeds, spicy, fatty and sour foods consumed the day before, and even highly carbonated mineral water). A large number of false positive results are obtained when testing at home.

False negative HIV test result indicates that the virus is present in the patient's blood, but antibodies have not yet been developed. When conducting a PCR analysis, a false negative result can be obtained in HIV-infected patients during the period of specific treatment, when the concentration of viruses in the blood is so low that it leads to the failure of the test system. In most cases, a false negative result is obtained due to a technical error or marriage in the test system, which is extremely rare due to strict quality control at all levels.

HIV testing should be postponed for at least two weeks after an infectious disease or vaccination.

Test systems that determine the presence of antibodies to HIV

Human immunodeficiency virus antibody testing evaluates the body's response to infection. For this purpose, enzyme-linked immunosorbent assay (ELISA, ELISA) is used, which allows to detect antibodies to the proteins of the virus and a confirmatory analysis of immunoblotting (western blot), which determines the reaction of antibodies to the proteins of the virus.

Antibodies to HIV

Human immunodeficiency viruses have antigenic properties and, when they enter the human body, cause the synthesis of antibodies - specific immunoglobulins. With the help of modern test systems in the blood serum and other biological fluids of an HIV patient, it is possible to determine the class of immunoglobulins (antibodies). The earliest (one week after infection) are IgM immunoglobulins. Their growth is noted within a month and then they remain for about 30 days. Immunoglobulins class IgG circulate in the blood for several years. Their detection is an indicator of the presence of HIV infection.

Antibodies to HIV appear after 2-4 weeks. after infection and then they are determined in the blood throughout the disease.

HIV window period

Antibodies in the body of an infected person are not produced immediately. At first, HIV infection does not manifest itself. Antibodies appear in the blood on average after 2-3 months from the moment of infection (from 2 weeks to 6 months). This period is called the “window”, when the antibody tests are still negative, but the viruses multiply intensively, and the patient himself becomes dangerous in terms of infecting contact persons. An infected person can be detected after a shorter (1-2 weeks) period after infection, for which polymerase chain reaction (PCR) is used. However, due to the high cost, this type of research is not used for screening.

ELISA in the diagnosis of HIV

In 90 - 95% of infected individuals, antibodies in the blood serum appear 3 months after infection. In a small part of patients (5 - 9%), antibodies appear in the period from 3 to 9 months and in 0.5 - 1% - at a later date. In the terminal stage of AIDS, the number of antibodies decreases significantly, and in some cases disappear altogether.

ELISA in the diagnosis of HIV is carried out in order to obtain a total spectrum of antibodies against HIV proteins (antigens) - p24 and gp160. Since 1985, this technique has been used on the territory of the Russian Federation for the purpose of mass research. It is simple to perform, shows fairly accurate results, and is cheap compared to other methods. In connection with the possibility of obtaining false positive results, all positive results are examined twice, after which the patient's blood serum is examined by a confirmatory test - an immune blot. This uses the same blood sample. In the presence of 2 positive results using ELISA and immunoblot in one sample, a diagnosis of HIV infection is made.

In the Russian Federation, ELISAs of the 4th generation are usually used. The test sees both antibodies (produced by the patient's body) and p24 antigens (proteins of the virus). The "window period" for the 4th generation tests is shorter. Within a month, you can get reliable results. However, more reliable, according to health experts, are the terms of 6, 8 or 12 (in the Russian Federation) weeks.

Rice. 8. In the photo, enzyme immunoassay analyzers.

Rice. 9. The photo shows an enzyme immunoassay analyzer.

For the primary examination of groups of people in order to detect HIV infection, only the ELISA method is used.

Immunoblotting method

The method of immunoblotting is more accurate than ELISA, according to most experts - the reference. With its help, antibodies to HIV proteins are detected in the blood serum. The technique is used to confirm the results obtained during the ELISA. Has high specificity. False positive results are rare. The reliability of the obtained results reaches 99%. Immunoblotting is an expensive technique and requires a highly specialized specialist conducting the study. It is possible to get questionable results.

The method is based on the separation of HIV antigens (proteins) using electrophoresis by molecular weight. Antibodies against capsid proteins are the first to be detected during infection. gag"(p24 and p17) and p55 precursor. They are followed by antibodies against supercapsid proteins. Env"(glycoproteins gp 160, gp120, gp41 and proteins p88) and non-structural proteins "Pol" (p31, p51 and p66). In some cases, antibodies against the genes " vpu», « vpr», « vif», « tat», « nef», « rev», « tat».

The blood serum of patients with HIV-1 and HIV-2 contains antibodies to all proteins of the viruses, but to confirm the diagnosis, only antibodies to proteins p24, gp41, gp120 and gp160 are determined in HIV-1, in HIV-2 - antibodies to proteins gp105, gp140 and gp36.

In the presence of 2 positive results using ELISA and immunoblot in one sample, a diagnosis of HIV infection is made.

Rice. 10. Apparatus for conducting research by the immunoblot method.

Rice. 11. Diagnosis of HIV infection is made in the presence of 2 positive results using ELISA and immunoblot in one sample.

Test systems for counting CD4-lymphocytes

One of the immunological tests used in HIV infection is the method of counting CD4 and CD8 lymphocytes in the blood.

CD4-lymphocytes (T-helpers) affected by immunodeficiency viruses. The gradual depletion of their population leads to a decrease in immunity and the patient's body ceases to resist infection. CD4-lymphocytes are counted by flow cytometry using automatic analyzers or manually using optical or fluorescence microscopy. The number of CD4-lymphocytes determines the start time of specific treatment (antiretroviral therapy) and the prevention of opportunistic infections, and evaluates the effectiveness of treatment.

When the number of CD4-lymphocytes in the blood serum is from 500 and below in 1 ml, it indicates the development of immunodeficiency.
With a decrease in the number of CD4-lymphocytes to 200 in 1 ml (the norm is from 600 to 1900 cells in 1 ml), acquired immunodeficiency syndrome - AIDS develops.
With a decrease in the level of CD4-lymphocytes to 50 and below in 1 µl, AIDS enters the terminal stage.

The proportion of CD4-lymphocytes among all lymphocytes in the norm is about 40%. A decrease to 20% indicates the development of AIDS.

CD8-lymphocytes(T-killers, in English. killer- killer) destroy HIV viruses by cytolysis. Their proliferation (increase in number) depends on the activity of T-helpers. With HIV infection, the number of CD4 and CD8 lymphocytes decreases, but the level of CD4 lymphocytes falls most of all. The CD4/CD8 ratio is normally 1.5 - 2.5. With a decrease in the number of CD4-lymphocytes, a decrease in the index is noted.

Its value less than 1 indicates a developed immunodeficiency, with a ratio of 0.6 - 0.8, AIDS develops.

Upon receipt of positive test results, a person must be registered with the state institution Center for the Prevention and Control of AIDS, where monitoring of his condition will be established and adequate specific treatment will be prescribed.

Rice. 12. In the photo, automatic flow analyzers are used to count CD4-lymphocytes in the blood of the subject.

HIV test using PCR

In recent years, the molecular genetic method for diagnosing HIV infection, the polymerase chain reaction (PCR), has become increasingly widespread. It is used to determine genetic material pathogen - RNA already 1 - 2 weeks after the alleged infection, and the high sensitivity of the test allows you to detect RNA viruses, even if there are only a few of them in the test material. This technique is expensive and therefore not currently used for screening. In addition, a significant problem of the study is the possibility of obtaining false positive results.

The essence of the PCR technique for HIV

The essence of this technique is to obtain multiple copies of the virus RNA (nucleic acid), which are subsequently detected both by their characteristic structure and with the help of labeled enzymes or isotopes.

Possibilities of PCR in HIV infection

Complete blood count for HIV

As a result of the defeat of human immunodeficiency viruses in the hematopoietic organs, hematopoiesis is inhibited, which is manifested by a decrease in the number of lymphocytes (lymphopenia), neutrophils (neutropenia), platelets (thrombopenia) and anemia. In addition, the destruction of cell populations is influenced by autoimmune processes that develop in HIV-infected patients. IgG immunoglobulins dominate in the blood serum of patients.

Rice. 16. Blood sampling from a vein and a finger for analysis.

Today, anyone can take an HIV test anonymously and free of charge in a matter of minutes, and modern equipment and trained personnel allow you to get the most accurate results.

Much attention is paid to the diagnosis of the immunodeficiency virus in the modern world. After all, the sooner a person learns about a terrible diagnosis, the sooner he can turn to specialists for professional help. Accordingly, treatment this disease could start earlier. Timely use of special antiretroviral therapy can significantly increase the life span of an immunodeficiency virus infected. It is important to note that in modern diagnostics There is a division into primary and secondary. Primary involves checking the patient with enzyme immunoassay. The result of ELISA for HIV, if necessary, is rechecked. How and why does this happen, and what might be the outcome of the primary research?

ELISA HIV negative, positive or doubtful: conditions for making a diagnosis and further actions of the patient

A positive ELISA for HIV does not always indicate that a person is infected. But before answering the question of why this happens, you should find out what the result of an enzyme immunoassay can be. The reliability of HIV ELISA is approximately ninety-eight to ninety-nine percent. This study has a small margin of error. During the analysis, blood is taken from the patient from a vein. Research is being done on an empty stomach. Next, the biological material is tested in the laboratory using special reagents and enzymes in order to determine whether its components react with artificial antibodies of the immunodeficiency virus. Despite the fact that the accuracy of ELISA for HIV is great, doctors and scientists involved in the study of the most terrible disease of the twenty-first century believe that only healthy people can be weeded out with its help. That is, those whose ELISA for HIV did not show a plus.

So, what can be the results of enzyme immunoassay, and what should the patient do when they are received:

ELISA for HIV negative. This may indicate that the person is healthy. The absence of antibodies in the patient's serum or plasma indicates that there is no immunodeficiency virus in his body. It should be remembered that this can only be judged if at least five weeks have passed since the alleged infection. And in some cases more. If the ELISA test for HIV is negative, but infection could occur, for example, through injecting drugs or unprotected intercourse with an untested partner, then infection is still possible. And it is better to check after a certain period of time. After all, how quickly the immunodeficiency virus will make itself felt depends on the state of the immune system and on the amount in which the infection entered the body. Medicine knows cases when the virus was detected more than six months after infection. Therefore, the reliability of ELISA for HIV after 3-4-6 months in certain cases remains in question. If the enzyme-linked immunosorbent assay showed a negative result, and the symptoms of the human immunodeficiency virus appear, we are talking about nausea and vomiting, diarrhea, aching joints and limbs, as well as an increase in body temperature, the check should be repeated. Perhaps the analysis was performed too early or an error occurred.

The analysis on a HIV IFA positive. This may indicate a possible infection. It is possible, because on the basis of enzyme immunoassay, conclusions about the presence of an immunodeficiency virus in a person are not made. If ELISA for HIV is negative, what does it mean? This means that the person is healthy. But a positive result does not always mean that the patient undergoing the study is sick. After all, the production of bodies in the body is possible in some other cases. The reliability of ELISA for HIV is high. So why is it impossible to make a diagnosis based on a positive result? The fact is that enzyme immunoassay is the primary diagnosis. Therefore, a person with a positive result is sent for re-examination using more sensitive methods.

Doubtful ELISA for HIV indicates that a mistake could have been made in the diagnosis. This can happen in both public and private medical institutions. Employees of clinics, laboratories and commercial organizations are people, and they tend to make mistakes. In rare cases, confusion can occur due to the fact that they can mix up the markers or the results themselves. The reliability of ELISA for HIV after 6 weeks is ninety-eight to ninety-nine percent. However, if there are symptoms and manifestations of the immunodeficiency virus, and the result is negative, the doctor may consider it doubtful and refer the patient for re-examination. This can be an enzyme immunoassay, immunoblotting, or a CITO test.

ELISA for HIV positive, immunoblot positive or negative: what do the results of testing with two methods say?

The reliability of ELISA for HIV 4 generations is high. However, before making a diagnosis, the patient is also referred for immune blotting. This is necessary in order to find out whether the antibodies that were detected by enzyme immunoassay enter into a stable reaction with antigens.

If the ELISA for HIV is positive, and the immunoblot is negative, then the infection has not been confirmed. In this case, the patient is referred for additional diagnostics to find out why antibodies are produced in the body and whether it is produced at all.

If the immunoblotting is positive and the enzyme immunoassay is the same, then the patient is diagnosed with immunodeficiency virus. After that, he is referred to a therapist or immunologist.

If the ELISA for HIV is negative after 6 weeks, but there are still doubts, the patient will be referred for immune blotting. The accuracy of these studies is the same. And there is an error in both enzyme immunoassay and immune blotting.

If the ELISA test for HIV, which is highly accurate, turns out to be negative, and the immune blot is positive, then the patient will also be given a terrible diagnosis.