FAQ: How accurate is the rapid oral HIV test?

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FAQ: How accurate is the rapid oral HIV test?

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FAQ: How accurate is the rapid oral HIV test?

Frequently Asked Questions

Q: How accurate is the rapid oral HIV test?

The rapid oral HIV test detects antibodies made by the immune system in response to HIV infection, just like the standard blood antibody test. The rapid oral test, however, detects these antibodies in oral fluid, and doesn’t require a blood sample.

The rapid oral HIV test is quite accurate (similar to the standard blood antibody test) for persons with chronic, or longstanding, HIV infection, but it is not as accurate for people with new or recent HIV infection. Like any antibody test for HIV, the rapid oral HIV test is not reliable during the “window period” (lasting several weeks to months) between the time a person is infected and the time the body has made enough antibodies for the test to detect. During this window period, someone who is infected might test negative for antibodies (a false-negative result). The “window period” for the rapid oral test is longer than it is for some HIV blood tests, meaning that for someone with acute or new HIV infection certain blood tests can detect HIV earlier than the oral rapid tests.

It also is possible to have false-positive results (a person may have a positive rapid oral HIV test result but not actually be infected with HIV). That’s why anyone who has a positive result with a rapid oral HIV test must have a more specific “confirmatory” blood test before a diagnosis of HIV infection can be made.

How accurate are rapid, point-of-care tests for HIV?

Key points

• Rapid tests are usually reliable for long-standing infections, but are sometimes unable to detect recent HIV infections acquired in the past few weeks.
• Many tests are based on older ‘second-generation’ technology, but a ‘fourth-generation’ test with better performance is available.
• Like any screening test, a reactive (‘positive’) result must be confirmed with one or two follow-up tests.

Rapid tests are often referred to as point-of-care tests because rather than sending a blood sample to a laboratory, the test can be conducted and the result read in a doctor’s office or a community setting, without specialised laboratory equipment.

Most point-of-care tests require a tiny sample of blood (the fingertip is pricked with a lancet). Other tests require oral fluid (an absorbent pad is swabbed around the outer gums, adjacent to the teeth). They are called ‘rapid’ tests because the result can usually be given within a few minutes.

Most rapid tests detect HIV antibodies. They are not part of HIV itself, but are produced by the human body in response to HIV infection. In the weeks after exposure to HIV, the immune system recognises some components of the virus and begins to generate HIV antibodies in order to damage, neutralise or kill it (this period is known as ‘seroconversion’). These antibodies persist for life.

The latest news and research on types of HIV tests

In contrast, the recommended laboratory tests also detect p24 antigen, a protein contained in HIV’s viral core that can be detected sooner than antibodies. Most rapid tests, with the exception of the  Determine HIV Early Detect and Determine HIV-1/2 cannot detect p24 antigen.

The accuracy of point-of-care tests is not always equal to those of laboratory tests, especially in relation to recent infection. This is for two main reasons:

• What the test looks for. While one antibody/antigen test is available, the other tests look for antibodies only. Moreover, some can only detect immunoglobulin G (IgG) antibodies, but not immunoglobulin M (IgM) antibodies, which appear sooner.

Basic information on better off knowing

• The sample taken. Point-of-care tests are usually performed on whole blood taken from a fingerprick. This has a lower concentration of antibodies and p24 than plasma. Samples of oral fluid have a concentration of antibodies that is lower still. (Plasma is the colourless fluid part of blood, separated from whole blood using laboratory equipment. Fingerprick blood is produced by pricking the finger with a lancet, whereas oral fluid is obtained by swabbing the gums.)

As a result, the window period of commonly used rapid tests such as the  Determine HIV Early Detect and the INSTI HIV-1/HIV-2 Antibody Test may be one to two weeks longer than for fourth-generation laboratory tests. Other rapid tests, based on older technology, may have longer window periods than this.

Rapid tests can be performed by staff with limited laboratory training. However, reading the test result relies on subjective interpretation, and when the result is borderline, experienced staff give more consistently accurate results. In a setting with low prevalence of HIV, staff may not see enough true positive samples to gain experience in interpreting test results.

It is good practice for test results to be re-read by a second member of staff, within the time frame specified on the test packaging. Organisations using point-of-care tests must maintain strong links with a pathology laboratory that provides support with clinical governance and quality assurance.

When used in a population with a low prevalence of HIV, false positive results can be a problem. The tests always produce a small number of false positive results, but in a setting where very few people have HIV, the majority of apparent positive results will in fact be incorrect. However, as the proportion of people with HIV being tested increases, the true positives start to outnumber false positives. This means it is more appropriate to use point-of-care tests in high-prevalence populations, such as with gay and bisexual men, than in the general population.

All HIV tests need to have reactive results (a preliminary positive result) confirmed with further tests. Most providers tell people who are testing that a negative result is definitive, but that a reactive result simply indicates the need for further laboratory testing.

Jump to

• Key points
• The accuracy of different rapid tests
• Window periods of rapid tests
• Situations in which rapid tests may not be accurate
• What do the test results mean?

The accuracy of different rapid tests

A wide range of point-of-care tests have been manufactured in many countries, but only a few of them have been subject to rigorous, independent evaluations, and even fewer are marketed in the UK. Research on HIV tests is only occasionally published in medical journals. Informally, laboratory professionals may have insights into which tests perform best.

It is important to verify that any test used is CE marked. This should mean that the test conforms to European health and safety legislation, although it does not necessarily mean that test performance has been independently evaluated.

There are variations in accuracy from one test to another, with some older tests that are not usually marketed in the UK having a sub-optimal sensitivity and specificity. However, evaluations by the World Health Organization of several rapid diagnostic tests that either have CE marks or are approved by the US Food and Drug Administration (FDA), indicate that most are extremely accurate. The key measures of accuracy are sensitivity (the percentage of results that are correctly positive when HIV is actually present) and specificity (the percentage of results that are correctly negative when HIV is not present).

Of note, in the World Health Organization data below, most tests were performed with samples of plasma or serum. However, the tests are less sensitive when testing whole blood sampled from a finger prick. There is one test (the OraQuick Advance Rapid HIV-1/2) which can also test oral fluid samples in addition to blood.

Also, the figures on sensitivity are based on samples from people who had chronic (not recent) HIV infection, but the tests are less accurate in cases of recent infection, especially those which only detect immunoglobulin G (IgG) antibodies.

There is one rapid, point-of-care test that looks for both antibodies and p24 antigen, in a similar way to antibody/antigen laboratory tests. The Determine HIV-1/2 Ag/Ab Combo was originally introduced in 2009, with an updated version that is now called the Determine HIV Early Detect launched in Europe in 2015 (the older version is still marketed in the United States and in some parts of the world).

The promise of having a ‘fourth-generation’ point of care test that detects p24 antigen is that the window period should be shortened. However, several studies found that although the older version of this test performed well in respect of established HIV infection, its ability to detect recent HIV infection did not match that of laboratory antibody/antigen tests. The test was quite insensitive to p24 antigen, making it only marginally better than antibody-only tests in detecting acute (recent) infection.

“All HIV tests need to have reactive results (a preliminary positive result) confirmed with further tests.”

The handful of studies published so far on the newer version suggests it has better performance in acute infection, although it still does not match that of antibody/antigen laboratory tests. The Determine HIV Early Detect’s sensitivity during acute infection has been variously estimated to be 28% (in three African countries), 54% (France), 65% (the Netherlands) and 88% (UK).

An analysis pooled the results of 18 separate studies in which a point-of-care test (including Determine, OraQuick, UniGold and INSTI) was compared with a more sensitive laboratory test. Compared with fourth-generation laboratory tests, the estimated sensitivity of the point-of-care tests was 94.5% (95% confidence interval 87.4-97.7) and specificity was 99.6% (99.4-99.7). Compared with RNA (viral load) tests, the estimated sensitivity was 93. 7% (95% confidence interval 88.7-96.5) and specificity 98.1% (95% CI: 97.9-98.2).

Sensitivity was higher in nine studies conducted in African countries than in the nine studies conducted in the United States and other wealthy countries. This is likely to be due to different populations coming forward for screening. Whereas 4.7% of those testing positive in African studies had acute (recent) HIV infection, this figure rose to 13.6% in the high-income countries.

Glossary

antibody

A protein substance (immunoglobulin) produced by the immune system in response to a foreign organism. Many diagnostic tests for HIV detect the presence of antibodies to HIV in blood.

point-of-care test

A test in which all stages, including reading the result, can be conducted in a doctor’s office or a community setting, without specialised laboratory equipment. Sometimes also described as a rapid test.

window period

In HIV testing, the period of time after infection and before seroconversion during which markers of infection are still absent or too scarce to be detectable. All tests have a window period, the length of which depends on the marker of infection (HIV RNA, p24 antigen or HIV antibodies) and the specific test used. During the window period, a person can have a negative result on an HIV test despite having HIV.

p24

An HIV antigen that makes up most of the HIV viral core. High levels of p24 are present in the blood during the short period between HIV infection and seroconversion, before fading away. Since p24 antigen is usually detectable a few days before HIV antibodies, a diagnostic test that can detect p24 has a slightly shorter window period than a test that only detects antibodies.

reactive

Because of the possibility that a positive result from a single HIV test is, in fact, a false positive, the result is described as ‘reactive’ rather than ‘positive’. If the result is reactive, this indicates that the test has reacted to something in the blood and needs to be investigated with follow-up tests.

A study in five African countries found that the performance of point-of-care tests was sub-optimal. Samples from some countries were more likely to have false positive results than others, suggesting that tests need to be locally validated and that some tests may be more accurate in relation to some HIV subtypes than others. The researchers found a high number of false positive results, whereas false negative results were relatively rare. The specificities of the First Response HIV Card Test 1–2.0, INSTI HIV-1/HIV-2 Antibody Test, Determine HIV-1/2 and Genie Fast HIV 1/2 were all between 90 and 95%. The findings confirm that the diagnosis of HIV should not be based on results from a single HIV rapid diagnostic test. A combination of HIV tests, and more specifically an algorithm (sequence) of two or three different tests, is required to make an HIV-positive diagnosis. This is recommended in testing guidelines.

All HIV tests need to have reactive (preliminary positive) results confirmed with confirmatory tests. A particular challenge healthcare workers have with rapid tests is how to communicate a reactive result to the person testing (who may be present while the result is being read) and explain that supplementary tests are needed. These problems are less frequently faced with laboratory testing – a large enough blood sample was taken to allow for it to be tested several times and for uncertainties in the diagnosis to be resolved.

Window periods of rapid tests

The window period refers to the time after infection and before seroconversion, during which markers of infection (p24 antigen and antibodies) are still absent or too scarce to be detectable. Tests cannot reliably detect HIV infection until after the window period has passed. All tests have a window period, which varies from test to test.

Delaney and colleagues estimated window periods for a handful of rapid tests in a 2017 study. However, all these estimates were based on testing blood plasma. In practice, tests are usually done on fingerprick blood (obtained by pricking the finger with a lancet) and the window period is likely to be several days longer.

The fourth-generation Determine HIV-1/2 Ag/Ab Combo was estimated to have a median window period of 19 days (interquartile range 15 to 25 days). This indicates that half of all infections would be detected between 15 and 25 days after exposure. Ninety-nine per cent of HIV-infected individuals would be detectable within 43 days of exposure.

The third-generation INSTI HIV-1/HIV-2 test was estimated to have a median window period of 26 days (interquartile range 22 to 31 days). This indicates that half of all infections would be detected between 22 and 31 days after exposure. Ninety-nine per cent of HIV-infected individuals would be detectable within 50 days of exposure.

Basic information on testing

Several second-generation tests, such as OraQuick Advance Rapid HIV 1/2, Clearview HIV 1/2 STAT-PACK and SURE CHECK HIV 1/2 were evaluated. The median window period was 31 days (interquartile range 26 to 37 days). This indicates that half of all infections would be detected between 26 and 37 days after exposure. Ninety-nine per cent of HIV-infected individuals would be detectable within 57 days of exposure.

UK guidelines take a cautious approach, describing the window period for all rapid, point-of-care tests as 90 days.

If you are testing with a rapid, point-of-care test and you are concerned that you may have been exposed to HIV during the test’s window period, you could also be tested with a fourth-generation laboratory test. This requires a blood sample, taken through a needle from a vein in the arm, which is tested in a laboratory using a more sensitive test. The results should be available after a few days.

Situations in which rapid tests may not be accurate

Performance of rapid tests is poorer in a number of situations. Results may not be accurate.

• In cases of recent HIV infection, during the test’s window period.
• In people with diagnosed HIV who are taking HIV treatment. These tests are not a reliable way to confirm that you still have HIV infection.
• In people who are taking pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP). If you acquire HIV, you may have a delayed antibody response, extending the window period.

What do the test results mean?

There are three possible test results:

1) Negative (may also be described as ‘non-reactive’). The test did not find any evidence of HIV infection. You probably don’t have HIV (so long as you aren’t testing in one of the situations described in the last section).

2) Reactive (often incorrectly described as ‘positive’ by manufacturers). The test assay has reacted to a substance in your blood. This does not necessarily mean that you are HIV positive. It means you need to take more tests to confirm the result. These extra tests are best done at a healthcare facility where they have access to the most accurate HIV testing technologies.

3) ‘Indeterminate’, ‘equivocal’ or ‘invalid’. The test result is unclear. Another test needs to be done.

when to do and which one is better?

Screening and confirmation tests.

Immunoblotting, ELISA and PCR. Accuracy of express tests and addresses for anonymous testing.

Everyone has an HIV status, only some are positive and others are negative. However, it is necessary to know it, especially in Russian realities, when there is an epidemic in the country, and already more than one percent of the population lives with the virus.

There are several types of tests for diagnosing the human immunodeficiency virus, and their classification is difficult only at first glance, in fact it is very logical. The main thing is to remember that, despite the high accuracy of the tests, not a single test will find the virus immediately after infection.

Screening (exploratory) tests

They help to suspect infection, but their results must be confirmed by other tests. Screening uses either antibody or antigen/antibody tests.

ELISA (ELISA) .

This method does not detect the virus itself, but the antibodies that our immune system produces to fight it.

There are several generations of ELISA:

• The first generation of tests used the virus itself, sonicated, and detected only HIV-1 antibodies. The analysis had low sensitivity and specificity.
• Second-generation ELISA was taught to detect antibodies to both HIV-1 and HIV-2. Synthesized proteins similar to real virus antigens served as the material. However, the first and second generation tests have not been used for a long time.
• Third-generation tests followed, which allow diagnosing long-term (chronic) HIV infection with a sensitivity and specificity of about 100%. However, in acute HIV infection (when there are few or no antibodies), their accuracy is considered insufficient.

A modern fourth-generation ELISA can detect antibodies that appear in the blood from the 30th (numbers according to the clinical recommendations of the Ministry of Health) of infection (according to the Center for Disease Control and Prevention in the US CDC – from 23 to 90 days). He conducts a combined analysis, at the same time checking whether there are protein “debris” of HIV (antigens) in the blood, as well as antibodies.

Due to its simplicity and low cost, this method is used most often, including rapid tests based on it.

Confirmation tests

As the name implies, they can be used to make sure that a person has or does not have HIV. Their disadvantage is complexity and high cost.

Immunoblotting helps verify screening results and determine if a person is infected with HIV-1, HIV-2, or both. This method has high accuracy and sensitivity, but is expensive and difficult to implement. It is a combination of ELISA and electrophoresis, which allows you to determine antibodies to specific HIV-1 antigens (gp160, gp120, gp41).

PCR (polymerase chain reaction) . The test is able to find the genetic material of HIV (DNA / RNA), that is, it checks whether the virus is directly in the blood. Nucleic acids can be detected as early as 7 days after infection (from 10 to 33 days according to the CDC).

In addition, PCR can be qualitative or quantitative. In the latter case, it is possible to monitor viral load (the concentration of the virus in the blood and other body fluids) in people with HIV, evaluating the effect of therapy.

Can I immediately have an immunoblot or PCR test to find out my HIV status?

Immunoblot is used by special laboratories of the AIDS Centers. Blood samples are sent there to recheck already positive primary screening tests. It will not work right away, even in paid clinics.

PCR, on the contrary, can be taken at any time, but only by contacting a commercial laboratory. In AIDS centers, it is also done to double-check a previously positive test. Yes, PCR allows you to detect HIV as quickly as possible (within 7-10 days after infection), but it also has disadvantages:

• high cost;
• can only detect HIV-1;
• in rare cases, detection of low levels of HIV RNA (eg, <1000 copies/mL) may lead to a false positive result.

This test is worth doing if:

• the person is suspected of having acute HIV infection (high risk of infection) or during the serological window;
• blood donors;
• newborns from HIV-positive mothers

How then is it correct to test for HIV?

According to the recommendations of the Ministry of Health, the initial analysis should be a screening ELISA test. If the result is positive, then another test is done in the laboratory using the same blood sample. If he is “with a plus”, then an immunoblot is already carried out.

Do I need to retest if the test result is negative?

Unfortunately, there is no universal recommendation. Repeated tests are needed to insure against getting into the window period, when there are no HIV antibodies and antigens in the blood yet, and the virus has already entered the body.

The same applies to the frequency of testing – it depends on various factors: the number of risks, the use of pre-exposure (PrEP) and post-exposure (PEP) prophylaxis, being in risk groups (injecting drug users, sex workers, men who have sex with men) . However, experts recommend checking every 6-12 months.

What can affect the result of an HIV test?

An HIV test may give incorrect results if:

• in the presence of systemic autoimmune diseases (collagenoses, vasculitis) and malignant tumors;
• when testing during the serological window – when antibodies to HIV have not yet appeared in the blood;
• due to a lab test error;
• after flu vaccination.

Babies born to HIV-positive mothers may retain maternal antibodies in their blood before the age of 18 months, which can lead to false positive results.

In addition, taking PrEP and PEP can affect the accuracy of tests, since antiretroviral drugs reduce the amount of the virus in the blood and antibodies to it.

In the case of PEP after the end of the course, it is recommended to consult a doctor and choose the optimal time for testing. The first test is usually carried out 4-6 weeks after exposure to HIV, then after 3 months, if necessary – after 6 months.

It is considered very important to get tested for HIV before starting PrEP and then tested every 3 months while already on PrEP.

Test results are not affected by food, alcohol or smoking. No special preparation required for HIV testing .

What about rapid tests?

They allow you to get tested for HIV without visiting a laboratory or clinic. In fact, these are third-generation ELISA tests that detect antibodies to HIV-1 and HIV-2 in saliva, urine or blood.

They are recommended to be done three months after the possible risk of infection (to avoid falling into the “window”). But they are considered reliable from the 30th day of the alleged infection (the period of the appearance of antibodies).

The figure shows how quickly the virus itself (its genetic material RNA), antibodies and antigens appear in the blood, as well as which testing systems can be applied.

The accuracy of most rapid tests for chronic (long-term) HIV infection is quite high (> 99% sensitivity and specificity), but still slightly below laboratory tests.

Today, saliva (or perigingival fluid) and blood tests are the most popular. You can either buy them yourself or get them free of charge from HIV service organizations.

Important to remember! If such a test turned out to be positive, the result must be rechecked as soon as possible with a more accurate method.

Where can I get an anonymous and free HIV test?

You can go to the local AIDS center, anonymous counseling offices or non-profit organizations (for example, the AIDS. CENTER Foundation Address: 11/1 Nizhnyaya Syromyatnicheskaya St., office 313). Or at the AIDS Center in the Moscow Region (Schepkina St., 61/2, building 8).

HIV testing is free and anonymous, no clinic registration or registration required. After passing the test, an identification number is issued, by which you can find out the result.

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Testing

TESTING

How is HIV diagnosis done? All about preparing and interpreting test results
HIV testing. Who should be tested and when?
What tests detect HIV
WINDOW PERIOD
Rapid HIV tests. Can they be trusted?

How is the HIV diagnosis done?

All about preparing and interpreting test results

HIV testing is a simple and painless procedure. How it goes, whether you need to prepare, what the test results show.

Voluntarily

HIV testing in most cases is voluntary, therefore it is carried out only after obtaining the informed consent of the patient.

How to get tested

Blood is taken for analysis in the treatment room. Blood is taken from the cubital vein in the amount of 3-5 ml into a sterile tube. Blood can be donated both in the morning on an empty stomach, and at any time of the day after a meal.

Risk of HIV infection during examination

Only disposable instruments are used in medical institutions, or they undergo high-quality sterilization. It is not possible to get HIV by donating blood.

Types of test results

There are three types of primary HIV diagnostic results – positive, negative and questionable.

If the result is positive

A positive result means that the test system detected antibodies to HIV in the blood sample, this may indicate that you really have HIV infection. A positive ELISA result must be confirmed in an immune blot with the same blood sample. In rare cases, the result is false positive. False-positive results occur with a viral infection in pregnant women, and with autoimmune diseases. A positive result may also be referred to as seropositive or HIV+ status.

If the result is negative

A negative result indicates that no antibodies to HIV were found in the blood – that is, there is no HIV infection. Or that HIV infection has occurred recently and the number of antibodies is below the threshold values ​​determined by the test system, that is, the “window” period lasts. If a dangerous situation regarding HIV infection has recently taken place, then it is advisable to repeat the examination after three months and six months. A negative result is also called seronegative, or HIV.

If the result is doubtful

Quite rarely test results are doubtful. This can be in two cases: when a person has recently become infected with HIV and the concentration of antibodies is insufficient for detection by conventional test systems, or when there is no HIV, but there are other chronic diseases – metabolic or autoimmune. Therefore, it is not advisable to test immediately after a dangerous contact. If a doubtful result was obtained during the examination by enzyme immunoassay, a confirmatory analysis is usually additionally performed using an immunoblot. If a questionable result persists, the examination is repeated after 1-3 months and the patient is observed for six months.

HIV testing.

Who should be tested and when?

Generally, an HIV test is strictly voluntary. However, there are circumstances when it is simply necessary to be tested for HIV infection.

In the eyes of society, HIV testing still looks unusual and even strange. It is possible that your friends and family, having learned about your plans to get tested, will suspect you of “bad” behavior. But in vain. Because testing for HIV is, first of all, a sign of taking care of your health.

Optional testing

HIV testing is voluntary in most cases. There are times when HIV testing is mandatory.

Sexual activity

Everyone who begins to have sex should be tested for HIV. It is optimal to find out the HIV status of a partner even before entering into an intimate relationship with him. If this was not possible, then it is necessary to be tested for HIV infection 3 months after the onset of sexual activity. The same applies to the situation of changing sexual partners. If the sexual partner is always constant for a long time, then there is no need for periodic HIV testing.

Examination after dangerous situations

In a situation of casual sexual contact with a partner whose HIV status is unknown, an informative determination of antibodies to HIV in the blood is possible only after three months. The first three months after infection with HIV, there is a “window” period when antibodies to the virus are just beginning to be produced and their level is below the threshold value determined by the test systems.

A similar situation is when infection through the blood is suspected, for example, when injecting drugs with an unsterile syringe. After dangerous, from the point of view of HIV infection, situations with negative results of the first examination, it is advisable to take repeated tests every three months during the year.

If there are signs of illness

Sometimes an HIV blood test is needed for clinical reasons, such as if a person is severely immunocompromised or has clinical signs that suggest HIV infection or AIDS. Examination is also recommended in case of detection of sexually transmitted diseases, hepatitis B or C, tuberculosis.

Representatives of certain professions

Representatives of a number of professions that work directly with blood and body fluids – doctors, laboratory assistants, nurses – a blood test for HIV infection should be done annually. In addition, medical workers of AIDS centers who are constantly in contact with HIV-positive people need to be examined.

Contacts with HIV-positive people

Testing is especially important for people who come into contact with HIV-infected people, including at home. People who have regular sex with someone who is HIV-positive should be tested every three months, even if they use a condom all the time.

After blood transfusion and transplantation

Patients who have received blood components (especially red blood cells) should be tested for HIV after three months. The same applies to those who have received donor organs and tissues.

Examination of pregnant women

Pregnant women also need to be tested for HIV in the early stages – when they contact the antenatal clinic. If the result is negative, testing is repeated in the third trimester of pregnancy to exclude the “window” period.

Examination of children born to HIV-positive women

As for children born to HIV-infected women, it is not advisable to conduct a blood test for HIV antibodies during the first 12-18 months. The fact is that during pregnancy, maternal antibodies to HIV are transferred with the blood to the fetus and remain in the child’s blood for up to 18 months, even in the absence of HIV infection. Thus, newborns either undergo PCR diagnostics of HIV, or after 18 months – an analysis for antibodies to HIV.

Screening people at risk for HIV

People at risk for HIV – homosexuals and commercial sex workers – should be tested for HIV every three months, whether or not they use a condom during sex. Drug users also need to be examined regularly, once every three months, including those who use non-injecting forms of drugs.

Re-examination

Repeated and further tests for HIV infection are determined by the specialist based on the results of the initial examination, clinical findings and depending on the situation.

What tests detect HIV? determine your HIV status.

There are several different tests, according to the results of which you can accurately understand whether there is a virus in the body or not, and questions about testing are probably the most relevant not only for HIV-positive people, but also for those who do tests for prevention.

Perhaps we should start with the evolution of HIV tests. The first HIV tests began in 1985. At that time, the main purpose of testing was to detect infection in donated blood. Since there was no cure for HIV at that time, there was no incentive to do this test either.

Subsequently, antiretroviral drugs were developed, which became a big step in the treatment of HIV infection. Therefore, they began to pay much more attention to testing, not only doctors, but also people who care about their health. In total, several generations of tests have been developed over the history of the development of HIV tests. Tests from the first to the third generation can only find antibodies in the blood. They are released into the blood by the immune system in response to the appearance of a foreign microorganism, in this case a virus. Most of these tests work by enzyme immunoassay (ELISA). Such tests are also called “indirect testing”. The first test detected antibodies using an sonicated virus called a lysate. This is the first test that could detect HIV in the body. However, he could only detect HIV1. And the test of the first generation was not too sensitive and specific, so it needed to be improved.

The next round of development in the study of HIV falls on the second half of the 20th century, more precisely in the 80s. Second generation tests were developed during this time. They could already detect antibodies to HIV1 and HIV2. Recombinant and/or peptide methods were used to determine the presence of antibodies. The recombinant method used genetically modified proteins that were similar to the protein antigens of the virus. The peptide method used fragments of proteins that were synthesized by an artificial, chemical method.

In the 90s, third generation tests appeared. Their main difference is that they have a higher sensitivity. This testing is based on the specific interaction of an antibody produced by the body and the hostile antigen of the virus.

Now the fourth generation test is most often used. He, like previous tests, detects antibodies, but at the same time, he is still sensitive to HIV antigens. This shortens the seronegative period and gives more accurate results.

Enzyme immunoassay or ELISA is currently the most popular and used. Its accuracy is about 99%. But besides enzyme-linked immunosorbent assay, other methods for determining HIV are often used. If the ELISA is usually carried out as a screening test, i.e. during the initial examination, then immune blotting is used to make an accurate diagnosis of HIV. It is much more difficult to carry out, but gives a more accurate result, because it is more sensitive and specific. For IB, blood from a vein is also used, after which it undergoes special processing, and then applied to a special strip of nylon filter or nitrocellulose. A reaction occurs and the result is displayed on the strip – it becomes visible. If stripes appear on certain places of the strip, then this becomes a confirmation that the blood contains antibodies to HIV.

Another method for detecting HIV in the body is the polymerase chain reaction (PCR). However, it is much more difficult to use and requires great skill. PCR analysis examines nucleic acids, and these are DNA and RNA, so it turns out that it determines the genetic material of a microorganism. This research method is very accurate – up to 98% – 99%. But you need high-quality reagents and highly qualified professionals who can correctly conduct a study and make a diagnosis.

These are currently the most popular HIV testing methods. As mentioned above, no test can give a result with 100% accuracy. Therefore, an additional method is always used for confirmation. Only by passing several testing methods will doctors be able to make a final diagnosis. What kind of testing will be carried out for the patient, the doctor also determines, based on the individual characteristics of the organism.

WINDOW PERIOD

Everyone, well, almost everyone, in life may have situations in which he is at risk of contracting HIV.

Unfortunately, sometimes such situations are extremely difficult to avoid, and they can arise absolutely spontaneously.

What to do if there is a suspicion, even the smallest, that you have become infected?

Of course, you need to be tested so that there is no doubt. And now, the test is over, the tedious waiting for the results has passed, and you are told that the results are negative. It would seem that it is already possible to calm down, but the doctor tells you about some mysterious “window period”, sometimes calling this incomprehensible “window” seronegative. And the fear begins to return. To avoid this fear, we will talk about the seronegative window – we will explain what this term means, how long this period lasts, and how to behave during this time.

So, the “window period”, seronegative, seroconversion window – is the period of time when an infectious agent (virus, bacterium, etc.) has already entered the body and multiplies, but antibodies have not yet appeared in the patient’s blood.

Currently, HIV tests do not detect the virus itself in the body. They can only determine the presence of antibodies or antigens (antibody is a protein that the immune system produces in response to the appearance of foreign molecules in the body. Antigen are molecular components that carry foreign genetic information).

But the body reacts differently to the appearance of the virus, and accordingly, it begins to produce antibodies at different times – from 2 weeks to 6 months. Antigens appear in the body immediately, but their concentration may be so low that the test cannot detect them, and during this period the person will receive a negative HIV test result. So it is this period – from the moment of infection to the appearance of antibodies – that is called the “window period”.

Therefore, doctors, in order to accurately determine the presence of HIV in the body, advise doing the test several times – 2 and 6 months after the moment when a person could become infected.

It is very important to remember that even if your tests show a negative result, but you suspect that you may have contracted HIV, you should be very careful until you have the final result of your test. Because the virus can live and develop in the body, be contained in the blood and secretions, and a person can be not only a carrier, but also a potential spreader of the disease.

If you suspect that you may have contracted HIV, you must understand and be aware that you now have a responsibility because you can infect people close to you.

Even if after a while it turns out that the fears were in vain, and the HIV test turned out to be negative, the precautions taken will not be superfluous. Because in this way you minimize the possibility of infection with other serious diseases. It is always important to remember about elementary preventive measures that will help you stay healthy and prevent people close to you from getting sick.

Rapid HIV tests. Can they be trusted?

How can this be avoided? It is very simple – you need to test for HIV at least once a year. To do this, in each city there are specialized centers where everyone can be examined and be sure of their status. But sometimes there are situations when it is not possible to promptly undergo a full-fledged medical testing. For such situations, they came up with an excellent solution – rapid HIV tests. With the development of technology, they are becoming more accurate and in many ways are not inferior to laboratory testing. Every year they become more and more, the choice becomes more diverse. In order for you to navigate this variety, we will try to tell you the main points about express tests.

You should start with the fact that there are 3 types of rapid tests:

– saliva sample;

– according to a urine sample;

– according to a blood sample.

The most popular rapid test is the saliva test. This is not surprising, because it is the easiest to use and does not require complex manipulations, or breaking the skin. In addition, this test minimizes the possibility of HIV transmission. It is a device that can only be used once. To determine the presence of human immunodeficiency virus, it is necessary to collect the near-gingival fluid – saliva. The result will be ready in 20 minutes. The test determines the presence of HIV types 1 and 2 in the body. The accuracy of the test is quite high, according to some reports it approaches 99%. However, according to experts, if the test gave a positive result, there is no need to sound the alarm and make a final diagnosis. In any case, for an accurate result, it is necessary to undergo an examination in a specialized institution.

The rapid test, which uses a urine sample to detect HIV, is less popular and is more of a complementary test than a primary one. It is very similar in form to a pregnancy test. You need to collect urine in a jar and dip a strip there. The result will be ready within 10-20 minutes.

And, finally, one of the most accurate, but the most “dangerous” express tests – on a blood sample. To determine HIV in the body, it is necessary to take blood from a finger and lower it into the device. The complexity of this test, on the one hand, is that it is necessary to break the skin, which means creating an additional risk of infection, on the other hand, the virus in the blood from a finger can be stored for no more than 2-3 minutes, so the material should be used immediately to determine the test results .

Rapid tests can also be done at home if there is a good reason for doing so. It must be remembered that in order to increase the accuracy of testing, it is necessary to observe precautions and disinfection, strictly follow the instructions. Well, if you read this instruction in full, you can see there information that in order to confirm the results of express tests, you need to re-test in a specialized center or in a clinic.