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A human immunodeficiency virus (HIV) test detects HIV antibodies or antigens, or the genetic material (DNA or RNA) of HIV in the blood or another type of sample. This can show if an HIV infection is present (HIV-positive). HIV infects white blood cells called CD4+ cells. They are part of the body's immune system that help fight infections. HIV can progress to acquired immunodeficiency syndrome (AIDS).
After the original infection, it takes about 4 to 12 weeks for HIV antibodies or antigens to appear in the blood. The period between becoming infected with HIV and the point at which antibodies or antigens to HIV can be detected in the blood is called the seroconversion or "window" period. During this period, an HIV-infected person can still spread the disease, even though a test will not detect any antibodies or antigens in his or her blood.
Several tests can find antibodies to or genetic material (RNA) of the HIV virus. These tests include:
This test is usually the first one used to detect infection with HIV. If antibodies to HIV are present (positive), the test is usually repeated to confirm the diagnosis. If ELISA is negative, other tests usually aren't needed. This test has a low chance of having a false result after the first few weeks that a person is infected.
This test finds either the RNA of the HIV virus or the HIV DNA in white blood cells infected with the virus. PCR testing isn't done as often as antibody testing, because it requires technical skill and expensive equipment. This test may be done in the days or weeks after exposure to the virus. Genetic material may be found even if other tests are negative for the virus. The PCR test is very useful to find a very recent infection, find out if an HIV infection is present when antibody test results were uncertain, and screen blood or organs for HIV before donation.
This test detects HIV antibodies using a special fluorescent dye and a microscope. This test may be used to confirm the results of an ELISA test.
If HIV antibodies or antigens aren't found, the test may be repeated in a few months.
If you have a positive test result, contact your sex partners to inform them. They may want to be tested. You may be able to get help from your local health unit to do this.
A test for the human immunodeficiency virus (HIV) is done to:
This test is not done to find out if a person has AIDS. A diagnosis of AIDS means that a person is HIV-positive and other problems are present.
In general, there's nothing you have to do before this test, unless your doctor tells you to.
A test for HIV infection can't be done without your consent. Most doctors offer counselling before and after the test to discuss:
Before the test, it's important to tell your doctor how and where to contact you when your test results are ready. If your doctor has not contacted you within 1 to 2 weeks of your test, call and ask for your results.
A health professional uses a needle to take a blood sample, usually from the arm.
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Your doctor may ask you to come back to talk about your results. This may happen no matter what your results say. It does not always mean that you have HIV.
Current as of: October 31, 2022
Author: Healthwise StaffMedical Review: E. Gregory Thompson MD - Internal MedicineAdam Husney MD - Family MedicinePeter Shalit MD, PhD - Internal Medicine
Current as of: October 31, 2022
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine & Peter Shalit MD, PhD - Internal Medicine
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