The United States Food and Drug Administration (FDA) regulates the tests that detect infection with Human Immunodeficiency Virus (HIV), the virus that causes AIDS. AIDS is a serious disease that can be fatal because the body has lost the ability to fight infections and cancers. There are a number of options for people to be tested for HIV, using tests approved by FDA:
Trained health professionals collect a sample and run the test in a professional medical setting. You receive your test results from a trained health professional.
You collect a sample in the home, forward the sample to a medical laboratory, and trained health professionals run the test in the medical laboratory.
You collect a sample, run the test, and obtain your own test results in your home.
HIV Tests For Screening and Diagnosis
HIV tests are very accurate, but no test can detect the virus immediately after infection. How soon a test can detect infection depends upon different factors, including the type of test being used. There are three types of HIV diagnostic tests: antibody tests, combination or fourth-generation tests, and nucleic acid tests (NATs).
Antibody tests detect the presence of antibodies, proteins that a person’s body makes against HIV, not HIV itself. Most HIV tests, including most rapid tests and home tests, are antibody tests. It can take 3 to 12 weeks for a person’s body to make enough antibodies for an antibody test to detect HIV infection. In general, antibody tests that use blood can detect HIV slightly sooner after infection than tests done with oral fluid.
Combination or fourth-generation tests look for both HIV antibodies and antigens. Antigens are a part of the virus itself and are present during acute HIV infection. It can take 2 to 6 weeks for a person’s body to make enough antigens and antibodies for a combination test to detect HIV. Combination tests are now recommended for testing done in labs and are becoming more common in the United States. There is also a rapid combination test available.
NATs detect HIV the fastest by looking for HIV in the blood. It can take 7 to 28 days for NATs to detect HIV. This test is very expensive and is not routinely used for HIV screening unless the person recently had a high-risk exposure or a possible exposure with early symptoms of HIV infection.
An initial HIV test will either be an antibody test or combination test. It may involve obtaining blood or oral fluid for a rapid test or sending blood or oral fluid to a laboratory. If the initial HIV test is a rapid test and it is positive, the individual will be directed to get follow-up testing. If the initial HIV test is a laboratory test and is positive, the laboratory will usually conduct follow-up testing on the same blood specimen as the initial test. Although HIV tests are generally very accurate, follow-up testing allows the health care provider to be sure the diagnosis is right.