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Learn about the three types of HIV tests, their accuracy and how to understand results

Before World AIDS Day, Thursday, December 1, learn about HIV testing, its importance, and the different types of tests. 

What is HIV testing?

An HIV test checks your blood or other body fluids to determine if you have HIV.

Getting tested is the only way to know if you have HIV, allowing you to start proper treatment and medication immediately.

How often should I get tested?

The Centers for Disease Control and Prevention (CDC) recommends all people ages 13-64 get tested for HIV at least once

Some people may need more frequent testing.

If you’re a sexually active, you should get tested every three to six months. If you have shared needles, syringes, or other drug injection equipment, you should get tested at least once a year.

Keep in mind your test results will be heavily influenced by the window period and type of HIV test you take.

What is a window period?

A window period is the time between exposure to HIV and when a test can detect HIV in your body. This can vary based on the test.

The window period for HIV testing can begin as early as 10 days after exposure but if tested too soon, some HIV tests are not guaranteed to be accurate. If you believe you were exposed, it is recommended to get re-tested after three months.

Can I do a self-test for HIV?

Yes – you have two options:

  • Rapid self-test: A rapid self-test can be done at home, and you can get results within 20 minutes. You can buy a self-test kit at your nearby pharmacy. In the U.S., the only rapid self-test currently available is an oral fluid test.
  • Mail-in self-test: A mail-in self-test includes a specimen collection kit containing supplies to collect dried blood from a fingerstick at home. The sample is then sent to a lab for testing – when ready, results are reviewed by a physician and sent to you on a secure platform electronically. You can order it online or have your doctor order it for you.

Is there more than one HIV test?

Yes – there are a variety of easy, painless and fast testing methods.   

Antibody Test (3rd Generation HIV Test)

The antibody test is usually a screening test, which looks for antibodies to HIV in your blood or oral fluid.

Most rapid tests and self-tests are antibody tests. 

  • How does this test work? Antibody tests use blood from a vein to detect HIV sooner after exposure compared to tests involving blood from a finger prick.  You’ll likely get a rapid HIV test if you get an HIV test outside a healthcare setting lab, mobile testing van or community health center.
  • Reliability: False-positive results and false-negative results can happen. In that case, confirmatory tests are done using fourth-generation antigen-antibody tests.
  • Results: Typically, available within 30 minutes. If the test returns negative, and you haven’t had a possible exposure during the previous three months, you don’t have HIV. However, if your test result is positive, you should visit your healthcare provider for a follow-up test.
  • Should I test again? YES! You should test again around three months after possible exposure to get a more accurate test result. This is the longest window period of the three tests because it takes time for your body to react to the virus and produce antibodies. 
  • Pros: A rapid test can be done from anywhere and does not require you to go to a lab to get the results. 
  • Cons: Test results are often unreliable, so you might need to get re-tested.

Antigen/Antibody Test (4th Generation HIV Test)

The antibody/antigen test, also called a fourth-generation HIV test, can detect HIV antibodies and p24 antigens. 

When a person contracts HIV, the immune system starts to produce HIV antibodies. HIV antibodies help the body fight the virus by responding to p24 antigens – part of the virus.  

  • How does this test work? Typically given at a clinic, this test involves either a blood sample from a vein or a drop of blood from your finger.
  • Reliability: Can detect HIV one month after infection.
  • Results: Within a few weeks or days. After a positive test, your healthcare professional will arrange a follow-up test to confirm the positive result. If the follow-up test is positive, you have HIV.
  • Should I test again? YES! You should test again between 18 to 45 days after possible exposure with a lab test (blood from a vein) or 18 to 90 days with a rapid or at-home test to get more accurate test results.
  • Alternative: The rapid version provides results in 30 minutes or less, but the window period can be as long as 90 days for an accurate result.
  • Cons: This test isn’t available for at-home testing.

Nucleic Acid Test (NAT)

The nucleic acid test, also known as a viral load test, is the only test of the three types looking for the actual virus in your blood.

It is expensive. The NAT is typically not used for initial screening but for monitoring HIV treatment.

  • How does this test work? At your HIV test follow-up, your provider will get a blood sample from your vein and send it to a lab for testing. 
  • Reliability: This test is 95-99% accurate, starting around nine to eleven days post-exposure and 99% accurate around 28 days post-exposure. 
  • Results: You can get results as early as 10 to 33 days after infection. This test has the shortest window period – meaning, you can get tested and know your status more accurately as early as ten days after possible exposure. 
  • Pros: A NAT can detect HIV sooner than other types of HIV tests.
  • Cons: The cost.

If you think you’ve been exposed to HIV in the last 72 hours, talk to your healthcare provider about post-exposure prophylaxis (PEP) – an HIV medicine to prevent HIV after possible exposure.

PEP is commonly prescribed by emergency room doctors, but if you don’t have a healthcare provider you can still have access.

Where can I get tested for HIV?

You can get tested for HIV and other STIs at your family doctor’s office or community health clinics. 

Click here to find a testing site, resources and more near you. 

If you or a loved one are experiencing HIV symptoms or are interested in getting tested for HIV, contact us today for inclusive and confidential care.