HIV test; human immunodeficiency virus antibody test, type 1
The test looks for HIV-1 antibodies in your blood.
Your body makes these antibodies when you have been exposed to HIV, the virus that causes AIDS.
Because the findings are not considered definite unless you have two tests, your doctor will likely do two types of testing on your blood sample:
ELISA (enzyme-linked immunosorbent assay), a highly sensitive screening test for HIV
Western blot, a test widely used to confirm the results
There is an HIV-2 virus, but HIV-1 is more common. When people say "HIV," they are usually referring to HIV-1.
You may have this test if you have symptoms of an HIV-1 infection. Early symptoms are flu-like and include:
Runny or stuffy nose
You may also have this test if you've had unprotected sex and want to find out if you are HIV-positive. Testing is important to protect yourself and others, since you can be infected with the virus even if you don't feel sick.
You may have this test if you have shared needles to inject drugs. Needle-sharing has been linked with the spread of HIV infections.
You may also have this test if you are diagnosed with a different sexually transmitted disease (STD). This is because STDs generally suggest the possibility of high-risk behavior.
Your doctor will also order a Western blot test if your ELISA test is positive. Your doctor may also order viral load testing if he or she suspects you have an acute HIV infection.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Normal results for the ELISA test are negative, meaning you have no HIV-1 antibodies in your blood. If the ELISA test is positive for HIV-1 antibodies, your doctor will confirm this result with a Western blot analysis of your blood.
Normal results for the Western blot test are negative. The Western blot uses electrical fields to find antibodies, and the results appear as bands on a computer screen. If two out of three bands appear, the test is considered positive.
If both the ELISA and the Western blot test are positive, it means you likely have HIV-1.
Because the test looks only for the presence of HIV-1 antibodies, you might be infected with HIV but get a false-negative result. ELISA may not find antibodies for weeks or even months after your exposure to the virus. Your doctor may have you repeat the test weeks or even months later if he or she suspects your result is false-negative.
You may have a false-positive result if you have an autoimmune disorder, recently received a flu shot, or are taking part in an HIV vaccine trial.
Depending on your results, your doctor may suggest that you speak with an HIV counselor.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Timing is important. Getting the ELISA test too soon after exposure to HIV-1 may give a false-negative result.
You don't need to prepare for this test.