What is the window period for HIV testing?

Key points

• This page gives information on how soon HIV can be detected by a blood test and when you can be confident in the result.
• The window period of modern laboratory HIV tests is 45 days.
• The window period of rapid, point-of-care tests and self-tests is 90 days.

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 always detect HIV infection during the window period.

All tests have a window period, which varies from test to test. It also depends on the specimen that is being tested: window periods are usually reported based on a sample of blood plasma, but are longer when the specimen tested is fingerprick blood or oral fluid.

(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.)

The latest news and research on types of HIV tests

There are two key questions to ask about a specific HIV test: 

• How soon after someone is exposed to HIV can the test detect whether they have HIV? (Some, but not all, infections may be detected at this stage).
• How soon after exposure to HIV can an individual be confident that a negative test indicates they do not have HIV? 

The information given in UK testing guidelines about window periods is based on answers to the second question – specifically, how long after exposure to HIV 99% of infections will be detected by a specific type of test. At this stage, it is highly likely that a negative result is accurate.

How long are the window periods of different HIV tests?

It is hard to say exactly how long the window period lasts, as there are variations between individuals and it is a difficult topic to research (recently infected people would need to know exactly when they were exposed to HIV and then give multiple blood samples over the following days and weeks).

Nonetheless, a study by Dr Kevin Delaney and colleagues calculated window periods for a range of HIV testing assays. All these analyses were based on plasma samples. Window periods are likely to be several days longer when testing samples of fingerprick blood or of oral fluid, as will be normal when using rapid, point-of-care tests and self-testing devices. Unfortunately, precise figures for how much longer the window periods are have not yet been published.

The researchers’ analysis confirms that fourth-generation laboratory tests (which detect both antibodies and p24 antigen) detect HIV infections between one and three weeks earlier than older antibody-only tests. Moreover, their data suggest that some countries’ guidelines which recommend retesting 90 days after a possible exposure to HIV are more cautious than they need to be.

A fourth-generation laboratory test is recommended in UK and US guidelines. It uses a sample of blood plasma or serum and can detect immunoglobulin G (IgG) antibodies, immunoglobulin M (IgM) antibodies and p24 viral antigen (a protein contained in HIV’s viral core that can be detected sooner than antibodies). Commonly used tests of this type include Abbott Architect HIV Ag/Ab, GS Combo Ag/Ab EIA and Siemens Combo HIV Ag-Ab.

• The median window period is 18 days (interquartile range 13 to 24 days). This indicates that half of all infections would be detected between 13 and 24 days after exposure.

• 99% of HIV-infected individuals would be detectable within 44 days of exposure.

UK guidelines state that 45 days is the window period for fourth-generation laboratory tests.

A fourth-generation rapid test is available (Determine HIV Early Detect or Determine HIV-1/2). While results for this assay when testing plasma were broadly similar to those of equivalent laboratory tests, the window period is likely to be several days longer when testing fingerprick blood, as the test is normally used.

A few third-generation rapid, point-of-care tests are available. They can detect immunoglobulin G (IgG) antibodies and immunoglobulin M (IgM) antibodies. Examples include the INSTI HIV-1/HIV-2 and Uni-Gold Recombigen HIV tests. The estimated window period for INSTI when testing plasma are as follows:

Basic information on testing

• The median window period is 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.

• 99% of HIV-infected individuals would be detectable within 50 days of exposure.

However, those estimates were based on testing plasma. In practice, tests are usually done on fingerprick blood and the window period is likely to be several days longer.

UK guidelines state that 90 days is the window period for all rapid, point-of-care tests.

Third-generation laboratory tests are no longer recommended for use. They can detect immunoglobulin G (IgG) antibodies and immunoglobulin M (IgM) antibodies, but not p24 viral antigen. Their window periods are similar to those of the INSTI third generation rapid test (plasma samples), but a little shorter (median 23 days).

UK guidelines state that 60 days is the window period for third-generation laboratory tests.

Many rapid, point-of-care tests are described as second generation. They can detect immunoglobulin G (IgG) antibodies, but not immunoglobulin M (IgM) antibodies or p24 viral antigen. As these two substances are detectable sooner after HIV infection than IgG antibodies, second-generation tests have longer window periods. Examples include OraQuick Advance Rapid HIV 1/2, Clearview HIV 1/2 STAT-PACK and SURE CHECK HIV 1/2.

• The median window period is 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.
• 99% of HIV-infected individuals would be detectable within 57 days of exposure.

However, those estimates were based on testing plasma. In practice, tests are usually done on fingerprick blood or oral fluid and the window period is likely to be several days longer.

UK guidelines state that 90 days is the window period for all rapid, point-of-care tests.

Glossary

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.

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.

plasma

The fluid portion of the blood.

immunoglobulin

Another name for antibodies. An antibody is a protein substance produced by the immune system in response to a foreign organism (such as bacteria, virus or parasite).

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.

No self-testing devices were included in this study. However, most self-tests are modified versions of rapid, point-of-care test kits that were originally designed for healthcare professionals. Most are based on second- generation tests, so are likely to have relatively long window periods. A few, including the INSTI HIV Self Test, are based on a third-generation test.

Similarly, self-sampling was not included. In the UK, this usually involve the user sending a sample of fingerprick blood to be tested in a laboratory with a fourth-generation antibody/antigen test. Plasma is extracted from the sample using centrifugation. In theory, the test will be as accurate with plasma from a self-collected sample of fingerprick blood as from venous blood, including in relation to acute (recent) infection.

Are these figures always accurate?

In some situations, these figures should be interpreted with caution:

• When tests are done with samples of fingerprick blood or oral fluid (rather than blood plasma), their window periods are likely to be longer.
• Individuals who are taking pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP) may have a delayed antibody response, extending the window period. 
• The data are based on individuals with HIV-1 subtype B (the form of HIV most commonly found in Western countries) and it’s possible that tests are less sensitive to other subtypes.

HIV Test Overview | HIV.gov

Content From: HIV.gov•Updated: October 13, 2022•5 min read

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What Can You Expect When You Get an HIV Test?

Your HIV testing experience might be a little different depending on where you get tested.

HIV Testing in a Health Care Setting or Lab

If you take a test in a health care setting or a lab, a health care provider or lab technician will take a sample of your blood or oral fluid. If it’s a rapid test (oral fluid or finger stick), you may be able to wait for the results, but if it’s a laboratory test, it can take several days for your results to be available. Your health care provider or counselor may talk with you about your risk factors, answer any questions you might have, and discuss next steps with you, especially if your rapid test result is positive.

• If the test comes back negative, and you haven’t had an exposure during the window period for the test you took, you can be confident you don’t have HIV.
• If your HIV test result is positive, the lab will conduct follow-up testing, usually on the same sample as the first.

HIV Testing Outside of a Health Care Setting or Lab

If you get an HIV test outside of a health care setting or lab (such as at a community-based organization, mobile testing van, or elsewhere) you will likely receive a rapid HIV test.

• If the test comes back negative, and you haven’t had a possible exposure during the previous 3 months, you can be confident you don’t have HIV.
• If your test result is positive, you should go to a health care provider to get follow-up testing. Counselors providing the test should be able to answer questions and provide referrals for follow-up testing as well. You can use the HIV.gov locator to find a health center near you.

Learn about the different places where you can get an HIV test.

Is HIV Self-Testing an Option?

Yes. HIV self-testing allows people to take an HIV test and find out their result in their own home or other private location. There are two kinds:

• A Rapid Self-Test is done entirely at home or in a private location and results are ready in as little as 20 minutes. You can buy a rapid self-test kit at a pharmacy or Exit Disclaimer. The only rapid self-test currently available in the U.S. is an Exit Disclaimer. Read the instructions included in the test kit before you start. There is a phone number included with the HIV self-test if you need help using the test.
• A Mail-In Self-Test includes a specimen collection kit that contains supplies to collect dried blood from a fingerstick at home. The sample is then sent to a lab for testing and the results are provided by a health care provider. You can order a mail-in self-test online. Your health care provider can also order a mail-in self-test for you.

Check to see if your local health department or other organization near you provides rapid self-tests for a reduced cost or for free. HIV self-tests and mail-in HIV tests may be covered by insurance. Be sure to check with your insurance provider and your health care provider about reimbursement for tests you purchase.

Note: State laws regarding self-testing vary and may limit availability. Check with your provider for additional testing options.

Learn more about HIV self-testing and which one might be right for you.

The COVID-19 pandemic has made it more difficult for some people to access traditional places where HIV testing is provided. Self-testing allows people to get tested for HIV while still following social distancing practices. You can buy a rapid self-test kit at a pharmacy or Exit Disclaimer, or ask your local health department or HIV service organization if they offer self-testing kits.

Can an HIV Test Detect the Virus Immediately After Exposure?

No HIV test can detect HIV immediately after exposure. If you think you’ve been exposed to HIV in the last 72 hours, talk to your health care provider about post-exposure prophylaxis (PEP), right away.

The time between when a person gets HIV and when a test can accurately detect it is called the window period. The window period varies from person to person and also depends upon the type of HIV test. Some tests can detect HIV sooner than others.

Types of HIV Tests and Their Window Periods

There are three types of HIV tests: nucleic acid tests (NAT), antigen/antibody tests, and antibody tests, and they all have different window periods:

• Nucleic Acid Test (NAT)—A NAT can usually tell you if you have HIV infection 10 to 33 days after exposure
• Antigen/Antibody Test—An antigen/antibody test performed by a laboratory on blood from a vein can usually detect HIV infection 18 to 45 days after exposure. Antigen/antibody tests done with blood from a finger prick take longer to detect HIV (18 to 90 days after an exposure).
• Antibody Test—An antibody test can take 23 to 90 days to detect HIV infection after an exposure. Most rapid tests and self-tests are antibody tests. In general, antibody tests that use blood from a vein detect HIV sooner after infection than tests done with blood from a finger prick or with oral fluid.

Ask your health care provider or HIV testing counselor about the window period for the test you’re taking and whether you will need a follow-up test to confirm the results. If you’re using a self-test, you can get that information from the materials included in the test’s package.

If you get an HIV test after a potential HIV exposure and the result is negative, get tested again after the window period. Remember, you can only be sure you are HIV-negative if:

• Your most recent test is after the window period.
• You haven’t had a potential HIV exposure during the window period. If you do have an exposure, then you will need to be retested.

What If You Can’t Pay for Your HIV Test?

As required by the Affordable Care Act, HIV screening is covered by health insurance without a co-pay. If you don’t have health insurance, some testing sites may offer free tests. Use CDC’s Get Tested to search for free testing resources.

HIV Testing – Hiv

For the most part, HIV causes no complaints and can often multiply unhindered in your body for years and slowly destroy cells in your immune system. The only way to know if you are infected or not is to get tested.

In case of the slightest doubt, get tested – so, if necessary, you can start ARV therapy in time , which will allow you to keep HIV under control and continue normal, full life .

Who needs to be tested?

Getting tested for HIV is just as normal as regular health checks. All sexually active people should be tested for HIV at least once in their lives.

Be sure to get an HIV test if:

• you have had unprotected sex
• you have had many sexual partners
• you have used syringes or needles that someone else has used before you
• injured at work or in an accident you have been exposed to the blood of another person
• you are pregnant
• /or TB

You need to get tested for HIV if you have been acting risky and have the following symptoms:0022

These symptoms may also occur with other diseases and do not mean that you have HIV. However, some people may have HIV without symptoms at all.

Tests for HIV testing can be ordered by any doctor . For certain indicator diseases and conditions, being tested for HIV is an indication.

How often should I get tested for HIV?

If you are acting risky you must be tested for HIV at least once a year. It is enough to do the test 1 time, if after receiving a negative result you did not behave risky and did not come into contact with HIV-infected blood.

HIV testing made easy

• HIV blood testing and counseling free of charge for everyone, regardless of health insurance.
• The testing procedure is relatively simple and painless. Depending on the type of test, blood is taken from a vein or from a finger.
• You do not need to make an appointment at an HIV testing and counseling room to take an HIV test.
• Blood sampling and consultation take about 15 minutes.

HIV testing is confidential

HIV testing and counseling are done in private. You can take the test anonymously at HIV Counseling and Testing Room . You do not need to disclose your name or other personal information. HIV testing at youth counseling centers is not anonymous, but only you and the doctor who performed the test know the results of the test.

What does an HIV test show?

An HIV test shows whether you are infected with HIV or not. The presence of the virus in the body can be determined by a blood test. If HIV enters the human body, then the immune system begins to produce antibodies that an uninfected person does not have. Depending on the type of test, whether there are antibodies to HIV in the blood (HIV-1 and HIV-2 antibodies, as well as IgM and IgG) and / or proteins that make up HIV.

What is a “window period”?

The window period, or window period, is the time after which HIV can be detected in the human body after infection. The length of the window period depends on the method of testing for HIV, that is, on what type of testing you are getting.

For example, in the case of laboratory diagnosis of HIV using immunoassay, both viral components and antibodies can be detected in the blood, the window period in this case is 3-4 weeks. The rapid test detects only antibodies to HIV, and the “window period” is 10-12 weeks.

If you have been acting risky and think you might be infected with HIV, don’t wait, get tested. If your test result is negative, make sure you are not in the window period. During the window period, the blood does not yet have enough antibodies needed to obtain a positive result. To be sure, do another test after the window period has passed.

Types of HIV tests

24)

2.

Rapid test

• tests blood from a finger or vein
• window period – 10–12 weeks
• detects HIV-1 and HIV antibodies – 2
• Test accuracy 95-99%
• Test result available in 1-2 minutes

3. HIV RNA detection

HIV RNA detection by polymerase chain reaction (PCR) is used to diagnose HIV in newborns. The window period in this case is approximately 1-2 weeks.

For HIV testing, you can also do a saliva test . Since saliva tests do not give such accurate results as blood tests, they are practically not carried out in Estonia.

HIV test result

Initial test result may be negative, positive or indeterminate.

Test negative

A negative test means you do not have HIV. If you have been acting risky and suspect you have HIV, make sure you are no longer in the window period and retest when it is over. In the case of a specific exposure to HIV, a definitive answer of non-infection based on antibody detection can be given after 6 months.

Test indeterminate

Indeterminate test result must be confirmed by an HIV reference laboratory. If the result of the confirmatory test is also inconclusive, then the test must be repeated.

Possible causes of a test with an indeterminate result: autoimmune disease, cystic fibrosis, pregnancy, transfusion of blood or blood components, liver disease, recent vaccination, seroconversion, or end-stage disease.

Positive test

A positive test means you are infected with HIV. Each initial positive result is cross-checked in the HIV reference laboratory using a more accurate method, that is, a confirmatory test is done. In some cases, the initial positive result may turn out to be a false positive, for example, in the case of an acute viral illness or in some systemic diseases.

Confirmatory test

The confirmatory test is always performed using venous blood, regardless of which method was originally tested. The diagnosis of HIV is made only by a positive result of a venous blood test confirmed by an HIV reference laboratory.

The HIV reference laboratory first tells the doctor who tested you the result of the confirmatory test. You will get your test result from your doctor, who should refer you to an infectious disease specialist who will prescribe you treatment for HIV. If you have taken the test anonymously and the test is positive, then the confirmation test will be done with the identification of the person. According to the law, the diagnosis must be immediately registered in the infectious disease information system managed by the Health Board.

Mandatory tell if you have HIV with your partner, with whom you have had sex and/or with whom you have shared needles and syringes. They need to know that they have been exposed to HIV and may be infected.

What does your HIV test result tell you?

A negative HIV test result will give you a sense of confidence. If your HIV test result is positive, you can quickly begin treatment that will allow you to continue living a fulfilling life .

All about the HIV test: when to do it and which one is better? – Polyclinic news – News

When to do an HIV test and which one is better?

Screening and confirmatory 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 (enzymatic immunoassay).

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 only HIV-1 antibodies were detected. 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.

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 US Centers for Disease Control and Prevention CDC – from 23 to 90 day). 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.

When to take an HIV test and which one is best?

As the name suggests, they provide a reliable way to verify whether or not a person has the HIV virus. Their disadvantage is complexity and high cost.

Immunoblotting helps to verify the results of screening tests and clarify whether 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 capable of detecting the genetic material of HIV (DNA/RNA), that is, it checks whether the virus is directly present 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 take an immunoblot or PCR to find out my HIV status?

As the name suggests, they provide a reliable way to verify whether or not a person has the HIV virus. Their disadvantage is complexity and high cost.

Immunoblotting helps to verify the results of screening tests and clarify whether 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 capable of detecting the genetic material of HIV (DNA/RNA), that is, it checks whether the virus is directly present 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 take an immunoblot or PCR 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 makes it possible 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 (for example,

This test makes sense 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?

The Ministry of Health recommends that the initial test 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.

Should I be retested 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 in the following cases:

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 an error during the test in the laboratory;

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 and alcohol intake or smoking. No special preparation is required before taking HIV tests.

What about rapid tests?

They allow you to get tested for HIV without going to 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).

Most rapid tests for chronic (long-term) HIV infection are fairly accurate (>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 HIV test anonymously and free of charge?

GBUZ SK “Regional AIDS Center” Stavropol

st. Lenina, 434, Stavropol, Stavropol Territory, 355029, Russia

8(8652) 56-77-01 Lineinaya, 70, Kislovodsk, Stavropol Territory, 357700, Russia

8 (879-37) 2-05-82

HIV testing is free and anonymous, attachment to the clinic and registration is not required.