How long after HIV infection will a blood test show, timing, results, types of tests. Principles of using PCR diagnostics for HIV PCR for HIV where you can get it

Description

Determination method Quantitative determination, PCR with real-time detection.

Material under study Blood plasma (EDTA)

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Determination of HIV type 1 RNA in blood plasma by PCR with real-time detection. The study is performed on equipment from Hoffmann-La Roche (Switzerland) using standardized technology with automated sample preparation.

A study of the concentration of HIV type 1 RNA in the blood, which is used to predict and monitor the effectiveness of therapy.

Human immunodeficiency virus (HIV) is the etiological agent of acquired immunodeficiency syndrome (AIDS). HIV infection can be transmitted sexually, through contaminated blood and blood products, or from an infected mother to her fetus. Between 3 and 6 weeks after infection, a short-lived acute syndrome usually develops, characterized by flu-like symptoms and high levels of viremia in the peripheral blood. In most cases, an HIV-specific immune response and a decrease in plasma viremia then develops, usually within 4 to 6 weeks after the onset of symptoms. After seroconversion (appearance of specific antibodies), a clinically stable asymptomatic phase begins, which can last for years. The asymptomatic period is characterized by a low level of persistent viremia in plasma and a gradual decrease in the levels of CD4+ T-lymphocytes, which subsequently leads to the development of severe immunodeficiency, multiple opportunistic infections, oncogenesis and death. In persons with established HIV-1 infection, quantitative measurement of the level of HIV-1 RNA in the blood is used for the purpose of prognosis and monitoring of antiretroviral therapy.

Analytical indicators:

Clinical specificity of the test: 100%, with a confidence interval of 99.6-100%.

Test sensitivity: from 20 copies/ml.

Linear test range: 20 – 1 * 10 7 copies/ml

Subtypes of group M and O (HIV-1) are analyzed.

Indications for use

The test is intended for use in the management of patients infected with HIV-1, in conjunction with clinical data and other laboratory markers of disease progression. The test is used for prognosis (based on baseline HIV-1 RNA levels) or to monitor the effectiveness of antiretroviral therapy (based on changes in plasma HIV-1 RNA levels over the course of antiretroviral therapy).

Caution: The test is not intended for screening for HIV-1 in blood and blood products or for confirmatory diagnosis of HIV-1 infection.

Interpretation of results

Interpretation of research results contains information for the attending physician and is not a diagnosis. The information in this section should not be used for self-diagnosis or self-treatment. The doctor makes an accurate diagnosis using both the results of this examination and the necessary information from other sources: medical history, results of other examinations, etc.

Units of measurement: the amount of detected human immunodeficiency virus type 1 RNA, expressed in C/ml (copies/ml). One copy of HIV-1 RNA corresponds to 1.67 International Units (IU) according to the first WHO international standard for HIV-1 RNA in nucleic acid detection tests (NIBSC 97/656).

Interpretation of the result:

• “not detected”: HIV-1 RNA is not detected or the value is below the sensitivity limit of the method (20 copies/ml). The result is interpreted as “HIV-1 RNA not detected”;
• < 20 C/ml (копий/мл): HIV-1 РНК выявлена в концентрации на пределе чувствительности метода, количественная характеристика в копиях/мл с удовлетворительной точностью невозможна;
• from 20 to 10000000 C/ml (copies/ml): The obtained value is within the linear range, the result is reliable;
• >10,000,000 C/ml (copies/ml): The result is interpreted as: “HIV-1 RNA was detected at the indicated concentration beyond the upper limit of the linear range; The test was performed at a dilution of 1:X.”

Please note that the turnaround time for PCR tests may be increased when confirmatory tests are carried out.

HIV PCR is one of the most informative methods of molecular genetic diagnosis. This method helps to identify various kinds of infectious ailments and diseases in the patient that are inherited. The same diagnostic method is applicable in the case of testing biomaterial for the presence of HIV, a serious disease that develops throughout the patient’s life. With medical assistance, PCR was among the recommended tests performed on a paid basis in cases of suspected human immunodeficiency virus. However, the reliability of the study is justified only in 80 out of 100 cases.

PCR diagnostics for HIV stands for polymerase chain reaction. To study this species, various types of biological materials are used. Among them is blood, in addition, secretion from the patient’s vagina or seminal fluid in men can be used.

Attention! Saliva is not used for PCR in diagnosing HIV. This approach is considered ineffective, since antibodies to HIV are in minimal concentration in this material. The same goes for urine, sweat and tears.

The indication for the described study is a double positive ELISA (enzyme-linked immunosorbent assay). Alternative assignments will be discussed later.

Details about the essence of the analysis

The PCR test for HIV is based on the ability of nucleic acid to reproduce independently. Living cells consist of protein and these same acids, in other words, RNA and DNA. Molecules act as guardians of the genetic code.
At a low concentration of viral particles (HIV) in the biomaterial, the sample does not include entire DNA chains (deoxyribonucleic acid), but only their components, called nucleotides. The analysis allows you to detect even minor remains of virus cells. It is this fact that explains the ability of PCR to demonstrate results in the early stages - several weeks after HIV infection.

The best results from polymerase chain reaction can be expected when examining venous blood. The sample is digested using equipment. The fractions are then subjected to enzymatic treatment. Reactive substances combine with viral DNA particles to duplicate it. The number of such elements increases according to the chain principle until their presence (not antibodies) in the patient’s blood becomes noticeable to laboratory technicians. None of the existing diagnostic methods work on exactly the same principle.

Reaction components

Using the PCR method, you can find out in advance about the development of the virus in the body. Why can’t it be called popular in the field of free medicine and done everywhere? The fact is that such an HIV test is very expensive and requires the following components:

• a deoxyribonucleic acid matrix including a DNA segment intended for amplification;
• two primers (for each chain segment);
• a chemically active polymerase component to accelerate the polymerization of viral particles;
• deoxyribonucleoside triphosphates;
• divalent magnesium particles (charged);
• a special solution to create favorable conditions, ensuring the proper level of acidity, salt concentration, and the number of magnesium particles in the liquid.

Attention! To protect the sample from overheating, a small amount of petroleum jelly is added to the material, which contains fats and, accordingly, a high boiling point.

The relatively high accuracy rate of the analysis is explained by its increased sensitivity, which stimulates a reaction to antibodies to other viruses.

Advantages and disadvantages of the PCR technique for HIV

To objectively evaluate the method, we present in the table below a number of advantages and disadvantages of the study:

Obviously, there are more advantages of the technique. If we evaluate the type of diagnosis from the point of view of the productivity of further treatment and the possibility of prolonging the patient’s life, PCR is the surest path to success.

Features of the analysis

The main feature of the described analysis is its ability to diagnose HIV early, which other research methods are not capable of. How many days after the suspected infection can I donate blood for PCR? Typically this time period is 10-14 days. Over the next 24 hours, the patient receives the result. Possible deviations in deadlines are explained by the individual operating conditions of diagnostic centers and clinics.

Purpose of the study

PCR is mostly carried out to detect HIV (human immunodeficiency syndrome). However, the test can also be taken if you suspect the development of sexually transmitted diseases. The same method is applicable in the case of diagnosing hereditary diseases.

PDR diagnostics: reasons for carrying out

When should you donate blood for PCR? In most cases, biological material is donated when the human immunodeficiency virus has adapted to the body’s conditions, stimulated the production of antibodies and caused the first symptoms of HIV. However, this is justified only if a sufficient amount of time has passed after infection and requires ELISA.

The need for PCR arises on the initiative of the patient who wants to promptly diagnose the disease (if there is one). The reason for this may be: unprotected sexual intercourse, contact with biological material of an infected person, recent blood transfusion, etc.

Who is prescribed PCR?

Determination of HIV infection using PCR, on the recommendation of a specialist, is carried out in the following cases:

• preliminary diagnosis. PCR accurately confirms or refutes the ELISA result;
• immunoblotting confirmed the diagnosis. Immune blotting is an additional way to study AIDS . Both methods are used together, which eliminates the possibility of misdiagnosis;
• with confirmed HIV status using PCR, the effect of the chosen treatment is monitored;
• for blood analysis of donors for the presence of HIV antibodies;
• to determine the HIV status of a newborn when the mother tests positive. PCR in the first days of life makes it possible to determine intrauterine infection or infection of the baby while passing through the birth canal. The test is performed 2–3 weeks after birth.

How long does it take to take a PCR test, and where can it be taken?

HIV PCR analysis is carried out in a special laboratory. The test itself and interpretation of the result do not require much time: a month or even a week. It takes up to 6 minutes to draw blood. In a normal case, a specialist will need no more than a day to make a diagnosis and issue a conclusion. The first 8 hours are spent studying the blood, the remaining time is spent on registration. The result can be collected the very next day after the sample is taken. The duration of express testing is 2 hours.

Attention! The compulsory medical insurance policy allows you to take the test for free at a public health care institution.

Almost any commercial laboratory is capable of conducting research, and on an anonymous basis. The person is assigned a special number, to which the results are then linked. This information is uploaded to the institution’s website in the user’s personal account.

How much does it cost to take a PCR test?

This method of conducting research is quite expensive. This is due to the fact that PCR must be carried out on the latest medical equipment; manipulation requires specialists to have a sufficient amount of knowledge.

The pressing question is: how much does it cost for a person to take a PCR test for HIV? This will require around $56-60.

Carrying out analysis

PCR testing for HIV involves:

• blood sampling for research;
• additional collection of sperm from a man and genital secretions from a woman.

Attention! As a result, the test allows doctors to determine a high viral load in order to monitor the patient’s condition.

Other features of this HIV test that should be taken into account:

• a couple of days before the test, the patient should reduce the amount of fatty foods in the diet;
• Blood is drawn on an empty stomach;
• Enzymes that synthesize various infections are added to the split biological materials in a special reactor;
• the analysis is carried out in several stages, since the division of molecules occurs in an arithmetic progression. A special program compares a large number of cellular structures to detect HIV.

Accurate diagnostic methods, which include PCR, are expensive, but are capable of detecting HIV in the early stages. In the treatment of such pathologies, the most important thing is a correct and timely diagnosis, which can improve a person’s quality of life and its duration.

Why is HIV and AIDS so scary, what diagnostic methods exist. In-depth information about PCR studies.

According to statistics provided by the World Health Organization jointly with the UN organization UNAIDS, over the past forty years, more than 25 million patients have died from HIV and AIDS. It is not for nothing that epidemiologists have dubbed HIV the plague of the 20th century, since the damage caused by this infection to humanity is colossal. The countries of the African continent were most heavily infected. The infection is hitting the economies of already unstable states hard, and the people are destitute.

When symptoms appear, prompt diagnosis is extremely important. infection of the body with HIV infection, because a timely course of therapy can save or at least increase the patient’s life. Nowadays, technological progress has come a long way: the newest methods for diagnosing the HIV and AIDS virus have been invented, treatment is available to any person on the planet, the reliability of tests is characterized by a small degree of error, and therapy is highly effective.

Diagnosis of HIV infection

In our country, identifying the presence of HIV infection in a patient’s body is complex of analyzes:

• Linked immunosorbent assay
• Immune blotting
• Polymerase chain reaction
• Express tests

Enzyme immunoassay.

Screening (ELISA test) is the initial stage of determining infection in the body. It is based on protein compounds of the virus formed under artificial conditions, which identify the antibodies produced by immune cells as a reaction to infection. A chemical reaction occurs between the reagents, as a result of which the indicator element changes color. This means the test result is positive. Information using this method can be obtained within a couple of weeks from the moment of infection. This method does not detect the presence of infection in the patient, but determines the antibodies produced to this infection. It happens that the production of antibodies starts 10-15 days after infection, but in the vast majority of cases later - after 1-1.5 months.

Information on such analysis is processed from two to ten days.

The reliability of diangosis for HIV is supported by IB analysis. An exceptionally positive IB test for the virus can serve as a compelling reason to confirm infection.

The essence of the analysis:

A venous blood sample is taken for analysis in the laboratory. The sample is additionally prepared, the protein compounds that are present in it are electrified in the testing chamber, and then they are distributed in the gel substance according to their molecular weight. A paper strip coated with the reagent is placed several times into the prepared sample. If there are antibodies to the virus in the sample, a chemical reaction occurs and lines become visible on the test strip. When 2 or 3 dashes of p24, gp41, and gp120 or gp160 appear, the test result is positive.

If a positive result is obtained from the IB analysis, with an error of one percent, a conclusion can be made about the presence of HIV infection in the body.

Rapid tests for HIV and AIDS

The latest technologies for determining the immunodeficiency virus in the body are express methods. Information on such an analysis can be obtained within a few minutes after completion. The highest reliability is found in immunochromagraphic tests - special test strips on the surface of which a layer of reagent is sprayed. Antibodies contained in the test material come into contact with the reagent, changing the color of the indicator. After a few minutes, two stripes appear, indicating the presence of infection. The presence of a single line means there is no infection.

Such a test can be used as an additional one; information on such a test is necessarily confirmed by other studies.

How much does a rapid HIV test cost?

An express test for HIV will cost on average 200-1000 rubles.

The PCR diagnostic technique was originally developed 35 years ago by the American scientist Kari Mullis. The inventor of the study received the international Nobel Prize in 1993 for his innovation. It has become indispensable for any laboratory activity.

PCR is used in molecular biology to make many copies (amplify) small sections of DNA. DNA polymerase can only add a nucleotide to a pre-existing 3-OH group. So he needs a primer to which he can add the first nucleotide. This requirement allows you to identify a specific section of the pattern sequence that needs to be diagnosed. At the end of the PCR reaction, a particular sequence will accumulate into billions of copies (amplicons).

PCR involves a heating and cooling process called a thermal cycle, which is performed by specialized equipment. Polymerase chain reaction (PCR) is a relatively simple technique. It enhances the DNA template to produce specific DNA fragments in vitro (in vitro analysis). Traditional methods of cloning a DNA sequence into a vector and replicating it in a living cell often require several days to several weeks of research. But you can get the results of DNA sequence amplification using PCR after a couple of hours.

Most biochemical tests used in the diagnosis of infectious diseases require a fairly large amount of biological material. For PCR this condition is not mandatory. Thus, PCR may provide more sensitive pathogen detection. And higher levels of amplification of certain sequences in less time with a fairly limited amount of biomaterial. These features make the technology extremely useful. Not only for basic research, but also for personal purposes. Including genetic identity testing, forensic testing, industrial quality control.

The main value of the analysis lies in the ability to identify sexually transmitted pathologies before the first signs develop. PCR analysis is used when early diagnosis of HIV infection is necessary. As well as determining the RNA of the virus in the donor’s blood. Due to the high sensitivity of the analysis, an answer can be obtained 7-14 days after the suspected infection. Diagnostic reliability will reach from 85 to 98%. However, the PCR test is not prescribed for everyone. Because it is a fairly expensive study. Most importantly, it requires expensive equipment and certain professional skills from laboratory staff. If the patient has not previously been in situations associated with an increased risk of infection, a polymerase reaction is not advisable.

Qualitative polymerase reaction for HIV

Carrying out high-quality PCR for HIV allows you to determine the presence of a viral disease in the body. The patient can receive the result in the form of the following marks: positive, false positive, negative. But the study does not make it possible to determine the number of copies of the retrovirus. Qualitative analysis is not performed on patients who have previously been diagnosed with an infection. It is not prescribed to monitor the effectiveness of antiviral therapy.

Quantitative PCR for HIV

It is carried out to determine copies of the RNA virus in the patient’s biological material. Quantitative PCR is prescribed only to patients with a previously identified infection, as a monitoring of ongoing treatment.

Real-time PCR

Used in laboratory diagnostics to form copies of DNA sections. Also for simultaneous quantitative research and detection of DNA sequence in biomaterial. Essentially, the diagnosis is quantitative PCR.

On a note!

In various laboratories you can find several diagnostic formulations: “PCR quantitative determination” and “Real-time PCR”.

Both analyzes are identical.

Taking material for HIV diagnosis

The collection of biological material for HIV diagnosis using PCR is carried out according to certain standards. The manipulation is carried out in the treatment room. Disposable sterile instruments are used. The package with instruments is opened directly near the patient. The collected material is placed in sterile tubes pre-treated with CrO3 (chromium mixture). The biological material is venous blood, which is donated in the morning and on an empty stomach. A few days before the test, you should avoid drinking alcohol, fatty and spicy foods, and stop taking medications.

If it is not possible to discontinue medications, this should be reported prior to testing.

Additionally, a smear from the urethra and vagina can be taken to identify concomitant sexually transmitted diseases. The study is conducted anonymously, and the patient receives the results personally. It is recommended to have your ID with you.

How long after you can take a PCR test for HIV?

It is possible to detect the presence of the HIV virus after 4-6 days after infection. In this case, the information content of the analysis will reach 85%. After 10-13 days, the analysis can determine the disease with an accuracy of 98%. A negative result will only be true if it is taken no earlier than 2 weeks after the suspected infection.

Reasons for a false positive result

Getting a false positive result is quite difficult.

This is possible if the rules for collecting biological material are not followed, the tubes are incorrectly labeled, the use of a low-quality test system and other similar factors. In other cases, the chance of obtaining a similar result is no more than 2%.

How long does it take to get test results?

From a technical standpoint, PCR results can be obtained within 4 hours. However, in practice, the patient receives a laboratory report from one to several days. In general, the timing depends on the workload of the laboratory and how organized its work is.

Carrying out a polymerase reaction in a newborn

PCR is prescribed when a child is born from an HIV-positive mother. Conducting ELISA in this case is not informative. Since a child retains antibodies against the retrovirus until about 2 years of age. For this reason, enzyme immunoassay will not give an accurate answer. If a PCR test is performed on a child aged 4-6 weeks and a positive result is obtained, we will be talking about infection.

If PCR performed between the ages of 8 weeks and six months shows negative results (provided that the child did not feed on mother’s breast milk), infection is excluded.

Why is PCR better than ELISA for detecting HIV?

The polymerase reaction makes it possible to detect the RNA of the virus and its presence in the body, including quantitative ones. The task of ELISA is to determine antibodies to HIV infection. The enzyme-linked immunosorbent assay is not inferior to PCR in determining possible infection; its accuracy reaches 99%. However, unlike PCR, it is not able to detect the disease in the early stages of its development.

Advantages of HIV PCR

• The polymerase reaction directly determines the presence of an infectious agent. For example, ELISA can exclusively detect antibodies and waste products of a microorganism.
• The assay clearly identifies a specific pathogen, even if there are several cross-reacting ones.
• The technique allows you to examine any type of biological material, including dried drops of blood.

One of the disadvantages of PCR is the increased sensitivity of the analysis. This sometimes causes a false positive result. This happens if even a small amount of foreign DNA is present in a test tube or on instruments.

Diagnosis of HIV using PCR and ELISA: interpretation, reliability of results

An enzyme immunoassay, in which the test results indicate the absence of antibodies to HIV and the p24 antigen in the body, is negative. If these molecules are present, a positive diagnostic conclusion is issued. In some cases, the patient may receive a false positive or false negative result. This is a consequence of early pregnancy, the presence of a herpetic infection, incorrect sampling of material, and disruption of the transportation of test tubes. In addition, similar results are found in patients with ongoing autoimmune diseases and various types of hepatitis. Western Blot (immune blotting), which combines ELISA and viral protein separation, can be performed.

Then a positive result will be in the presence of the viral infection glycoprotein gp160. It is a precursor to the HIV envelope glycoproteins gp41 and gp120. If these molecules are missing, the laboratory test result is considered negative. Carrying out Western Blot in combination with ELISA allows you to obtain results whose reliability exceeds 98%. In the case when the ELISA is positive and the Western Blot is negative, the testing is considered doubtful and requires PCR.