CDC INFO

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We hope you find the following information about HIV testing helpful.

There are 3 types of HIV tests:

Nucleic acid tests (NATs),
Combination antigen/antibody tests (also known as fourth-generation tests), and
Antibody tests.
Some tests check for HIV infection in the blood, and some use a swab to check for HIV in oral fluid.

First, it is important to know that NO test can detect HIV immediately after a person is infected. The time between infection and when a test can detect the presence of HIV is called the window period, and it varies depending on the type of test.

Nucleic Acid Test (NAT)

Nucleic acid tests (NATs) look for copies of the virus in blood. A NAT can detect infection very early, as early as 7 days after infection. NATs are used for HIV testing in many laboratory settings. NATs are often used for people who are at high risk for HIV infection and have symptoms of early-stage HIV.

The window period for a NAT is 10 to 34 days.

Antigen/Antibody Tests

Antigen/antibody tests (also known as fourth-generation tests) look for both HIV antigens and HIV antibodies in blood or oral fluid. Antigens are a part of the virus and appear in certain body fluids when a person is first infected with HIV, and before antibodies develop. Antibodies are part of a person's immune response to HIV and appear in certain body fluids later. This antigen/antibody test will often detect HIV earlier than a standard antibody test.

The window period for antigen/antibody tests performed by a laboratory on blood from a vein is 18 to 45 days. Antigen/antibody tests done with blood from a finger prick can take longer to detect HIV (18 to 90 days).

Antibody Tests

Antibody tests only look for antibodies in your blood or oral fluid. The 2 FDA-approved home test kits are antibody tests.

The window period for antibody tests is 23 to 90 days after infection.

All Tests

If you get a negative HIV test result during the window period of the test, you should get retested after the window period for the test you're taking to be sure. If your health care provider uses an antigen/antibody test performed by a laboratory with blood from a vein you should get tested again 45 days after your most recent exposure. For other tests, you should test again at least 90 days after your possible exposure to HIV. If you're sexually active, continue to take actions to prevent HIV, like using condoms the right way every time you have sex. Or choose to not have sex. And if you inject drugs, never share needles or other injection equipment.

If you get a positive HIV test result, a follow-up test will be conducted to be sure you have HIV. If you had a rapid screening test, the testing site will arrange a follow-up test to make sure the screening test result was correct. If your blood was tested in a lab, the lab will conduct a follow-up test on the same sample.

The only way to know if you have HIV is to get tested. If you may have been exposed to HIV, visit your healthcare provider, local clinic, or an organization that provides HIV testing as soon as possible. If you need help finding a testing site near you,

Visit gettested.cdc.gov,
Text your ZIP code to KNOW-IT (566948), or
Contact your local health department.
You can also get a home testing kit from a drugstore or online. There are 2 FDA-approved home tests: the Home Access HIV-1 Test System and the OraQuick HIV Test.

A negative result does NOT necessarily mean that you don't have HIV. That's because of the window period-the time between when a person may have been exposed to HIV and when a test can accurately tell for sure whether they have HIV. The window period varies from person to person and is also different depending upon the type of HIV test.

Ask your healthcare provider about the window period for the test you're taking. If you're using a home 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 for the test you're taking to be sure. For example, if your health care provider uses an antigen/antibody test (also known as a fourth-generation test) performed by a laboratory with blood from a vein you should get tested again 45 days after your most recent exposure. For other tests, you should test again at least 90 days after your most recent exposure to tell for sure if you have HIV.

If you learned you were HIV-negative the last time you were tested, you can only be sure you're still negative if you have not had a potential HIV exposure since your last test. If you're sexually active, continue to take actions to prevent HIV, like using condoms the right way every time you have sex and taking medicines to prevent HIV if you're at high risk.

For more information, please visit the following CDC website:

HIV Testing
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Division of HIV/AIDS Prevention
https://www.cdc.gov/hiv/basics/testing.html

HIV/AIDS: Laboratory Tests
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Division of HIV/AIDS Prevention
https://www.cdc.gov/hiv/testing/laboratorytests.html

HIV Risk Reduction Tool (BETA)
https://wwwn.cdc.gov/hivrisk

National HIV and STD Testing Resources
Centers for Disease Control and Prevention
https://gettested.cdc.gov/

Male Condom Use
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
https://www.cdc.gov/condomeffectiveness/male-condom-use.html

HIV/AIDS
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Division of HIV/AIDS Prevention
http://www.cdc.gov/hiv/default.htm

[Kirstie_MHModerator]

I'm not sure why this was posted, but just to be clear to the rest of the members, this is copied/pasted from the website, and the OP here is not a representative of the CDC.