HIV testing has come a long way, and today there are several quick and simple ways to get tested. But not all HIV testing is the same or offers the same accuracy or advantages.

One in seven people who have HIV infection don’t know it. If you’re thinking about getting tested, the fourth generation tests done by a lab are more reliable and have benefits over older tests.

The most important reason to consider a fourth generation HIV test is that it can detect HIV infection earlier and more accurately. This allows you to get treatment sooner and potentially prevent the spread of HIV infection to others.

Read on to learn more about the fourth generation HIV test.

The fourth generation HIV test, also called an enzyme-linked immunosorbent assay (ELISA) test, is a more complete screening that can identify acute HIV. This is the time when the virus is multiplying rapidly and you’re more likely to pass the infection.

In the first few weeks after exposure to HIV, your body produces an antigen known as p24. This protein is only present in people who have acute HIV infection. It triggers your immune system to respond.

The fourth generation tests can identify both HIV-specific antigen p24 and HIV antibodies with a blood sample.

The fourth generation tests require a blood sample that’s sent to a lab for testing. Blood testing done by a lab is the most accurate type of test.

There are many products approved for fourth generation testing, including:

  • ADVIA Centaur HIV Ag/Ab Combo (CHIV) Assay
  • Elecsys HIV Combi PT
  • Genscreen ULTRA HIV Ag-Ab
  • VITROS HIV Combo Test

The healthcare clinic or doctor’s office you visit for an HIV test can tell you more about the exact test they use.

There are several types of tests that can test for the presence of HIV. HIV testing can be done by drawing blood from a vein, a finger stick, or taking an oral swab of fluid.

Tests can measure antibodies, antigen/antibody (fourth generation), and there’s also a nucleic acid test (NAT). The NAT test can identify HIV and viral load (amount of virus in the blood). It can tell if you have HIV within around 10 to 33 days of exposure.

Older generation HIV tests and home test kits can’t detect acute HIV because they only detect antibodies produced by your immune system. Antibodies to HIV aren’t produced until several weeks after exposure.

Older tests like the third generation tests aren’t reliable until about 3 months after exposure to the virus.

This can delay getting treatment if you’re positive and increase the risk of passing the virus unknowingly. An estimated 40 percent of new HIV infections are transmitted by those who don’t know they’re positive for HIV.

The only Food and Drug Administration (FDA) approved home test kit, called the OraQuick In-Home HIV Test, tests for HIV antibodies with an oral saliva swab. Results are ready in 20 to 40 minutes.

However, if you take a home self-test, you’ll need to follow up with a clinic or healthcare professional for a confirmation test, as a negative saliva test doesn’t necessarily mean that you don’t have HIV.

This test only detects antibodies, not the virus itself, so it only applies to infections of several weeks or longer. Your doctor or the clinic you visit will do follow-up testing to confirm your results.

The main difference with the fourth generation tests are that they can identify HIV present in your blood several months earlier than older HIV tests because they detect both antigen p24 and antibodies.

The fourth generation test is different because it’s a combination test that’s more advanced. It can detect both HIV antibodies and the p24 antigen, which is associated with HIV. Testing for p24 allows earlier detection and diagnosing of acute HIV infection.

For a fourth generation test, you’ll have a small sample of blood drawn from a vein with a needle. You might feel a small sting from the needle. It takes a few minutes to take the sample. Once the sample is collected, it’ll be tested in a lab.

Results are available in a few days or in some cases, a few weeks.

Currently there no HIV tests that can detect the presence of HIV immediately.

Once someone is exposed to the virus, the body starts producing antibodies, this is called seroconversion. HIV tests can’t reliably detect the virus during the window period — the time from when a person gets the infection to when tests can detect the virus.

This time can vary from person to person. Testing too early will give false negative results, meaning you have the virus, but you test negative.

In some people, the virus can be detected within 2 weeks of exposure, depending on the type of test. The fourth generation test can detect p24 within 1 month of exposure. If you test before the average window period of 18 days, you may get a false negative test.

If you think you’ve been exposed to HIV, it’s important to contact your healthcare provider or visit a health clinic to get tested and begin prevention treatment if needed. If you receive a negative test, be sure to do a follow-up test.

Your healthcare provider may start you on the pre-exposure prophylaxis (PrEP) medication protocol as a prevention measure. PrEP medications can reduce the risk for infection, if started within 72 hours of high risk exposure.

What to expect during a 4th generation HIV test

  • The fourth generation test is done with a small sample of your blood, which will be drawn from your arm using a needle or from a finger stick. This sample is then sent to a lab by your healthcare provider or the clinic where you were tested.
  • Generally, you can expect results in a few days, but depending on the lab, it may take a bit longer.
  • If you receive a positive result, you’ll get a second test to confirm the result. Once positive results are confirmed, your doctor will review your treatment plan. It’s important to let sexual partners know to get tested as well.
  • Talk to a healthcare professional before and after the test to understand the results and any next steps required.
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The fourth generation test is reliable and highly accurate.

The reliability of tests depends on:

  • when you get tested (too early may not detect the presence of virus)
  • which test is used (antibody or antigen/antibody)
  • the individual (how your body responds to HIV)

The test needs to be done after the window period to avoid false negatives. The fourth generation test done with a blood sample from a vein can detect virus from 18 to 45 days from exposure.

You can get a false positive HIV test. This is when a person who doesn’t have HIV tests positive.

Newer tests like the fourth generation test are more accurate, but false positive and false negative (testing negative when you have HIV infection) results can happen for many reasons.

False positive results can happen if:

  • the testing sample is contaminated
  • the lab misreads or mislabels the test
  • you’ve been part of a HIV vaccine study

Keep in mind, testing blood versus saliva may also affect accuracy of results.

If you receive a positive result, your doctor or clinic where you were tested will recommend a second test to confirm results. This will guide next steps in the process.

Types of HIV tests

There are many different types of HIV tests, including finger stick, saliva, and blood drawn from a vein.

Here are the major types of tests:

  • Antibody test. This looks for antibodies in blood or saliva. It’s available as rapid test or self-test kits. They can take 23–90 days to detect post exposure.
  • Combined HIV antigen and antibody tests (fourth generation tests). They test for p24 and antibodies. They’re available as rapid finger prick or blood draw from a vein. It takes 18–45 days to detect post exposure for blood draw and 18–90 days for a finger prick test.
  • Nucleic acid tests (NAT). This test looks for HIV presence in the blood and how much virus is in the blood (viral load). This is done with a blood draw and the most expensive of all types of tests. It can detect the virus within 10–33 days of exposure.
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There are many options to get tested for HIV with the fourth generation test, including free clinics.

Some options include:

  • your doctor
  • a medical clinic
  • family planning clinic
  • hospital
  • sexual health clinic
  • community health center

The Centers for Disease Control and Prevention (CDC) website has a search tool to locate the nearest testing site by zip code.

Generally, there are no risks to the fourth generation test. It’s exactly like any normal blood work or testing done by your healthcare provider during regular checkups.

Occasionally, there may be rare complications:

  • infection from the needle
  • bruising at the blood draw site
  • feeling dizzy or lightheaded (especially if you have anxiety about needles)

Let your healthcare provider know if you’re afraid of needles and if you have any blood disorders that might increase your risk when blood is drawn. If you have any problems after the blood draw, contact the medical office where the test was done.

Talk with your healthcare provider or other testing center to understand false negative and false positive results and the importance of getting a second confirmation test.

If you think you’ve been exposed to HIV, getting tested will help you start treatment sooner and prevent the spread of the infection.

HIV (human immunodeficiency virus) is a virus that attacks your immune system. It’s transmitted through blood, semen, breast milk, and vaginal and rectal fluids. Early testing is a crucial step toward treatment and reducing transmission.

There’s no cure for HIV, but many medications are available both for prevention and treatment. New treatments are allowing people to live longer with an undetectable viral load. This means that the virus can’t be detected in the blood by lab tests.

Some symptoms of an acute HIV infection include:

These aren’t all possible symptoms of an acute infection. Contact a clinic or your doctor if you think you’ve been exposed to HIV to get tested.

You can learn more about HIV language and what different words mean here.

The fourth generation HIV tests are accurate tests that can detect HIV sooner. They’re more reliable than rapid tests and home self-tests. Faster detection is a major benefit.

If you’ve been exposed to HIV or are at high risk, routine testing is important. Testing can help you understand and take steps to protect yourself and others from HIV infection.

If you test positive, you can start treatment sooner. New treatments are helping people lead longer, healthier lives.