PCR tests for HIV: reliability and features of the procedure. Testing for HIV using the PCR method: when to take it, what is the accuracy of PCR diagnostics of HIV-associated infections
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Polymerase chain reaction in modern venereology and urology it is very often used to diagnose various STIs. PCR testing for HIV infection has also become widespread nowadays.
At the Private Practice clinic you can get tested using the PCR method in two main options:
- Qualitative PCR test for HIV - determines the presence or absence of the immunodeficiency virus in a person’s blood. The analysis usually takes 3-5 days, often faster if the result is negative. Costs 5000 rubles.
- Quantitative PCR diagnostics of HIV detects not only the presence of the virus, but also its quantity in 1 ml of the patient’s blood, that is, the so-called viral load. Allows you to monitor the effectiveness of treatment and build tactics for treating the disease. The analysis is usually ready within 5-7 days.
No special preparation is required to perform this analysis. It is advisable, of course, not to eat fatty foods the day before and to come on an empty stomach so that there is not a large amount of fat in the serum, which can interfere with the detection of HIV by PCR.
You need to come to the Private Practice clinic, you can pre-register, but you can also do this test without an appointment. The venereologist will fill out the referral form in room 2. Next, you will be taken to the treatment room, where, using a special vacuum system, almost painlessly, a nurse will take blood from the cubital vein for HIV PCR. The entire process from filling out documentation to drawing blood takes no more than 10 minutes.
You can receive the diagnostic result either by email or in person by picking up an HIV test form at the clinic. If the analysis is positive - only in person!
There are several types of tests for HIV and AIDS that cost much less and are done faster:
- Express method
- HIV ELISA
- Immunoblotting
- Immunogram
What are the advantages of PCR diagnostics of HIV:
- The most specific test for HIV infection, directly determining the RNA of the human immunodeficiency virus, and not antibodies to it and antigens.
- The earliest test that can detect infection in the first weeks after possible infection, unlike other methods that may not show the presence of the virus for up to 306 months or more.
- It is possible to determine the amount of HIV in a person’s blood, that is, its activity. What is important for further treatment and prognosis of the course of the disease.
You can get tested for HIV using the PCR method every day at the Private Practice Clinic, without weekends or holidays.
In addition to determining HIV using the PCR method, you can undergo any diagnosis of STIs, urological and gynecological diseases, and get advice from highly qualified specialists - venereologists, urologists and gynecologists.
Doctor of the clinic "Private Practice" dermatovenereologist, urologist Volokhov E.A. talks about PCR for HIV.
One of the most accurate and reliable methods of molecular genetic diagnostics is PCR, that is, polymerase chain reaction. This method makes it possible to diagnose various types of hereditary and infectious diseases in a patient.
PCR research allows you to diagnose one of such complex diseases as, which is difficult to treat. The reliability of HIV PCR is justified only in 80 cases out of 100.
The main way to diagnose HIV infection in a person’s body is through his blood, that is, testing for this disease is carried out. The simplest and most common diagnostic method is to take venous blood and conduct it in a special laboratory. Of course, the positive result obtained may be false, so it is rechecked in a more accurate research way in a reference laboratory.
Polymerase chain reaction is considered a rather expensive procedure, and its implementation requires special equipment and highly qualified specialists. It is for this reason that it has not become widespread among the population.
The use of PCR analysis to diagnose HIV allows you to obtain an accurate and reliable result about the presence of the disease, however, this often depends on the preparation of the patient himself.
PCR analysis is carried out in the following cases:
- Diagnosis of HIV infection in newborns born from a mother infected with AIDS.
- To control the concentration of HIV in the patient’s blood
- Testing of donor blood.
Even if the PCR test shows a positive result, a diagnosis cannot be made using this test alone. Most often it is used as an additional method for resolving controversial situations.
PCR analysis, unfortunately, cannot be called a universal method, the implementation of which gives accurate results on the presence or absence of infection in the human body. This is due to the fact that this type of research is more likely than other methods to produce false positive results. This diagnostic method is used when diagnosing a disease or testing for HIV infection. It is mainly used as an auxiliary method for diagnosing the AIDS virus.
However, despite the likelihood of a false-positive result, such an HIV test has a number of advantages over other diagnostic methods. PCR analysis can be carried out as early as 11-15 days after the date of suspected infection, and all other methods make it possible to assess the presence of the AIDS virus in the human body only after a long period of time. This discrepancy is explained by the fact that most HIV screening tests are based on detection of the virus, the formation of which occurs within three months.
The main difference between PCR testing and other diagnostic methods is the fact that it does not detect the virus, but the presence of the virus itself in the patient’s body.
It is for this reason that the polymer chain reaction method can be called ideal if there is a need for premature detection. In addition, this method can be used in cases where the presence of antibodies cannot be a reliable indicator.
More information about HIV testing can be found in the video.
If it is necessary to identify the degree or severity of pathology in the human body, they resort to conducting a quantitative PCR study. It is this that allows you to obtain information about the level of infection concentration in the patient’s body. The progression of the disease is accompanied by a gradual increase in the concentration of the virus, and quantitative PCR diagnostics makes it possible to determine the stage of infection and the effectiveness of the treatment. Diagnosing the “viral load” before identifying the disease and after treatment allows us to draw a conclusion about how effective the treatment is.
Other HIV diagnostic methods
Today, diagnosing HIV infection is a standard procedure that involves the use of various types of diagnostics:
ELISA test systems
Carrying out such a screening test makes it possible to detect the virus within a few weeks after it enters the human body. Such a study is not aimed at determining the presence of the virus in the patient, but at diagnosing the production of antibodies to it. There are several generations of ELISA tests, each of which has different sensitivity. Such a test sometimes gives results, which is explained by improper processing and the presence of various types of pathologies in the patient’s body.
Immune blotting
If the immune blotting shows a positive result, then we can talk about making a final diagnosis of HIV. The main way to carry it out is to use a nirocellulose strip on which proteins of viral origin are applied.
Express methods
This is considered a novelty in the field of diagnosing HIV infection and the results can be assessed within a few minutes after they are performed. The most accurate and reliable results are obtained by immunochromatographic tests, the use of which is based on the principle of capillary flow.
We can talk about the presence of HIV infection in the body only after confirming ELISA tests with IB analysis.
Diagnosing HIV infection in a person’s body makes significant changes to his usual lifestyle and relationships with others. It is the responsibility of the medical staff to save the test results, and only the patient himself makes the decision about who to inform about his illness. PCR is one of the diagnostic methods that allows one to detect the presence of a virus in the human body in just a few weeks.
A dangerous disease that is rightly called the “plague of the twenty-first century.” That is why enormous amounts of money and resources are spent on the fight against this disease, as well as on its research. The fact is that the immunodeficiency virus has not yet been fully studied. New discoveries are allowing scientists to develop vaccines and drugs to combat it. In modern medicine, much attention is paid to methods of diagnosing this disease. Doctors all over the world recognize PCR as one of the most effective ways to detect the virus. For HIV, this method is carried out through DNA testing. What is this study, what is its reliability and how to prepare for the analysis?
What is an HIV test - PCR?
First of all, you should decipher this abbreviation. Polymerase chain reaction (PCR method for HIV) is a diagnostic that has not been widely used in free medicine in our country. There are several reasons for this. But the main thing is that such research is not cheap. Moreover, its effectiveness is approximately eighty percent, when enzyme-linked immunosorbent assay and immunoblotting have higher reliability. It ranges from ninety-five to ninety-eight percent. Naturally, HIV can be detected using PCR. It is also used for other purposes. Using DNA and RNA studies, genetic and hereditary diseases, as well as infectious and viral illnesses are determined.
What is PCR for HIV, the reliability of which, as mentioned above, is only eighty percent, and why did this diagnostic method receive such a name? For this type of research, several types of biological material are used. This is primarily blood when it comes to the immunodeficiency virus. Also, to take an HIV test using the PCR method, secretions from the female genital organs and sperm are used. In this case, saliva is not examined. Because it is ineffective. Saliva contains a small number of virus cells. The same can be said about urine, sweat and tear fluid.
Does HIV PCR detect antigen or not? This question is often asked to medical professionals. The answer cannot be positive. Since this diagnostic method is aimed at studying DNA and RNA. Qualitative PCR for HIV is performed in a certain sequence. The necessary biological material is collected from the suspected infected person. Most often, venous blood is taken for such a study. By the way, the patient is not recommended to eat fatty foods for several days before this. The study is performed on an empty stomach. The biological material is placed in a special laboratory reactor, where it is broken down. Next, certain enzymes are added to the biological material (they are different for each disease or pathology). In order to synthesize a copy of a microbe, virus or infection, these enzymes bind to their DNA.
This happens in several stages according to the principle of a chain reaction. First, from one molecule of deoxyribonucleic acid, two are obtained, why four, and so on. Upon completion of several cycles of research, the laboratory technician receives hundreds or thousands of copies of the DNA of the material being studied, thanks to which he can easily compare them with the DNA of any pathogenic organisms, infections and pathologies at the genetic level, including the immunodeficiency virus. Thanks to this study, patients can take a PCR test for HIV type 1 or 2. It can also be used to determine the concentration of virus cells in human blood. If the PCR test for HIV is positive, but it was not preceded by immunoblotting or ELISA screening, then the patient is referred for these types of studies. If the polymerase chain reaction was preceded by one of the above types of research, then specialists in the field of medicine have no doubt. In this case, the person is given a specific diagnosis. If the PCR test for HIV is negative, but doctors still have doubts, the patient may also be referred for additional tests. It is worth noting that a false positive result in the case of this diagnostic method is detected more often than a false negative one. It is important to know that PCR testing for HIV is not performed using the smear or scraping method.
Where can I get a PCR blood test for HIV, and can it be done for free?
As mentioned above, research of this type is not very common in Russia. And the reason for this is its high cost. This allows us to conclude that it is impossible to take a PCR test for HIV (the reliability of PCR for HIV type 2 and type 1 is the same) in a regular public clinic. To do this, you will have to contact a specialized laboratory or a paid clinic. In large cities there are specialized AIDS centers where PCR tests are performed on a commercial basis. In smaller settlements, not everyone has the opportunity to undergo this type of research, but residents of such places can always visit large cities to pay attention to their own health.
How soon should I take a PCR test for HIV after suspected infection?
Medical specialists are often asked about how long it takes to get a PCR test for HIV. In this case, there is no difference between the studies. Both polymerase chain reaction and ELISA immunoblotting tests should be performed no earlier than three to four weeks after suspected infection. There is no point in conducting research before this period. PCR will not detect HIV after 10 days.
In some cases, the infection can be detected earlier or later than the specified period. But this depends on the specific characteristics of the organism being studied. It is important to know that polymerase chain reaction can detect not only infected people, but also carriers of the virus. The timing of HIV PCR depends largely on the laboratory in which the diagnosis is made. On average they are no more than a day. But there is also an express test that is necessary for blood transfusions or in emergency medicine.
The role of PCR diagnostics of HIV infection in neonatology
The HIV PCR test is used in neonatology when infected women give birth to children. Everyone knows that in this case the risk of transmission of the virus from mother to child is extremely high. All newborns whose mothers are infected or carriers of the immunodeficiency virus already have antibodies to the immunodeficiency virus in their blood at the time of birth, regardless of whether infection has occurred or not. Using PCR diagnostics for HIV, it is possible to identify whether they are the so-called defense of the immune system or a consequence of infection. This type of research is not performed in the first days of infants' lives. After all, if infection occurs during birth through the birth canal, then the immediate analysis will not be able to detect the disease. He will show it only if the infection was intrauterine. The accuracy of HIV PCR in newborns is also approximately eighty percent.
Timely detection of human immunodeficiency virus (HIV) is the key to successful antiretroviral therapy. Proper treatment allows you to lead a quality life for more than 70 years by controlling the viral load in the body.
The only way to detect the virus is to conduct laboratory tests with the collection of venous blood from the patient. We invite you to find out how long after infection a blood test will show HIV, and what to do if you receive a positive result?
If there is even a small chance of infection, both partners must be tested for HIV. The development of infection is individual, and the viral load will be different in two patients.
If your partner takes an HIV test and gets a negative result, this does not mean you are healthy. And, on the contrary, giving a positive diagnosis to your partner does not mean that you are infected.
Venous blood sampling allows detection of antibodies produced by the body in response to the virus. Testing is recommended for both partners at the same time. Remember, the sooner you find out about infection, the greater the results that can be achieved with therapy.
Phases and symptoms of the disease
How long does it take for HIV symptoms to appear? The first signs are observed 14-21 days after infection.
Name of phase of HIV development | Characteristic symptoms | What do you need to know? |
Incubation |
-cough, -headache, – increased fatigue, -high body temperature, – rashes, – general malaise. |
After 2-3 weeks, the listed symptoms disappear and the person’s condition returns to normal. |
Hidden |
Characterized by a complete absence of symptoms. A person may not realize for a long time (5-10 years) that the virus is multiplying in his body. |
It is impossible to determine the infection by symptoms. The only way to detect it is by passing special medical tests that determine the amount of antibodies. |
Secondary |
-temperature increase, – enlarged lymph nodes, – rash on the skin and mucous membranes, -enlarged liver – gastrointestinal disorders, – active development of infectious diseases. |
Symptoms appear for a while, after which they disappear again and the patient’s condition improves. However, the infection continues to develop in the body. |
Terminal |
It is characterized by a complete weakening of the immune system - it is not able to give any immune response. |
In the terminal phase of HIV, AIDS develops. |
How long does it take for AIDS to appear? Symptoms of the disease
After unprotected sexual intercourse or from the moment of infection by other means, the virus multiplies in the human body, increasing the viral load. Lack of treatment (antiretroviral therapy) leads to the development of AIDS after 10-12 years.
Attention! With proper HAART and following all doctor’s recommendations, it will be possible to control the viral load and slow down the transition of the virus to the AIDS stage.
Symptoms of AIDS:
- frequent infectious diseases,
- pale skin,
- hair and teeth loss,
- joint pain,
- fragility of bone tissue (high probability of fractures).
Types of HIV tests
You can donate blood for HIV at a public clinic, a private laboratory or at special AIDS centers. The type of analysis determines the preparation for blood sampling, the duration of the laboratory test, and the likelihood of obtaining a false result.
Immunoblotting
Immunoblotting (Western blot) is a highly sensitive method for recognizing HIV, the essence of which is to separate the proteins of the virus. They are transferred to a nitrocellulose membrane, and then the antigens, which differ in molecular weight, are compared with the samples on the test strip.
A feature of immunoblotting is the ability to determine the stage of infection, which allows immediate treatment to begin. When to take an HIV test using this method? It is usually prescribed when a positive or indeterminate result of RPGA and ELISA is obtained.
Express analysis
A rapid test of blood, urine and saliva can quickly detect the presence of the virus. The result of the study of biological fluids becomes known within 1-1.5 hours from the moment of delivery. The disadvantage of this method is the high probability of an unreliable result if the infection occurred recently.
PCR diagnostics
PCR diagnostics detects the virus at the DNA level and is the most accurate way to determine infection. The probability of obtaining an unreliable result is only 1%.
The PCR diagnostic result is known 3 days after blood collection. The peculiarity of the technique is that it is based on identifying the cells of the virus itself, and not searching for produced antibodies.
Linked immunosorbent assay
Enzyme-linked immunosorbent assay (ELISA) is based on the detection of antibodies to HIV. Venous blood is collected (strictly on an empty stomach!), which is checked for the presence of antibodies produced by the body.
ELISA is the most common method for diagnosing HIV.
How long does it take for HIV tests to be ready?
The results of most HIV tests become known within 3-10 days from the moment they are taken. The period is determined by the level of material and technical equipment of the laboratory and the degree of its workload.
Before taking the analysis:
- NOT eat food 8 hours before your appointment, donate blood on an empty stomach;
- NOT drink alcohol;
- NOT drink sparkling water, juices and other drinks, with the exception of pure water and unsweetened tea;
- NOT take antibiotics and other medications.
In what cases is it necessary to do an HIV test?
Regular testing to detect infection is recommended for homosexuals, medical workers and children if they were born to an HIV-positive mother.
Testing for the human immunodeficiency virus is necessary:
- after unprotected sexual contact with an unverified partner,
- after rape
- with enlarged lymph nodes and sudden weight loss,
- with frequent viral diseases,
- after blood transfusion, soft tissue or internal organ transplantation,
- when a partner is diagnosed with HIV.
What to do if HIV is still detected?
If HIV is detected, immediately contact a specialist from the Center for Prevention and Control of AIDS. He will issue a referral for a medical examination to identify concomitant diseases and possible complications.
Based on the results of tests and examination, an antiretroviral therapy regimen is drawn up. It consists of daily intake (2-3 times a day) of drugs that suppress the replication of the virus.
If there was a risk of contracting HIV, when can you get tested?
The first signs of infection in 70-75% of patients are observed 14 days after infection ( sore throat, fever, fatigue). Unfortunately, most infected people attribute them to a cold.
A blood test for the use of the PCR method is taken after 2 weeks from the moment of suspected infection. When carrying out standard ELISA testing, the virus can be detected only after 3-5 months.
During this period, the virus develops and multiplies in the body, which leads to an increase in the viral load and allows the infection to be detected. It is important that each person has an individual incubation period.
If the result is negative, then there is no need to worry anymore?
If the test results yield a negative diagnosis, but more than six months have passed since the suspected infection, the likelihood of infection remains. It is recommended to re-donate venous blood another 3 months after the initial test.
The reasons for a false negative result may be due to a low rate of virus reproduction (increased viral load), certain diseases, or non-compliance with recommendations before donating blood.
You don't have to worry if, after taking another HIV test, the negative result is confirmed.
What should I do if the test result is negative but I still have symptoms?
Unfortunately, identifying HIV by symptoms is not allowed. The diagnosis is established only based on the results of laboratory tests (immunoblotting, ELISA, etc.). If a negative diagnosis is confirmed by secondary analysis, then the symptoms that appear are the result of other diseases.
How reliable is a positive test result?
The probability that a positive test result is false is reduced to 1% for the analysis when diagnosing using the PCR method. With other studies, the risk of obtaining a false positive result is much higher, so repeat tests are carried out when confirming the diagnosis!
Reasons for a false positive result:
- diabetes,
- pregnancy,
- oncological diseases,
- STD,
- hepatitis.
What is an indeterminate result?
An indeterminate result means the presence of at least one set of proteins to the virus in the immunoblot. It is usually installed if the infection has occurred recently and the patient has a low viral load.
If the result is indeterminate, a repeat test is taken after 3 and 6 months. During this entire period, the patient is under the supervision of a doctor.
Decoding the results
The performance of the test systems differs (depending on the chosen analysis), but when 3 main sets of proteins are detected, a positive diagnosis is made.
Results of venous blood donation:
So, HIV can be determined in the body only through tests. Do not hesitate to donate venous blood if there is a possibility of infection!