A human immunodeficiency virus (HIV) test detects antibodies to HIV or the genetic material (DNA or RNA) of HIV in the blood or another type of sample. This determines whether an HIV infection is present (HIV-positive). HIV infects white blood cells called CD4+ cells, which 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 between 2 weeks and 6 months for antibodies to HIV to appear in the blood. The period between becoming infected with HIV and the point at which antibodies 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 in his or her blood.
Several tests can find antibodies to or genetic material (RNA) of the HIV virus. These tests include:
Testing is often done at 6 weeks, 3 months, and 6 months after exposure to find out if a person is infected with HIV.
A test for the human immunodeficiency virus (HIV) is done to:
The Centers for Disease Control and Prevention (CDC) recommend HIV screening as part of routine blood testing. You and your doctor can decide if testing is right for you.
This test is not done to determine if a person has AIDS. A diagnosis of AIDS means a person is HIV-positive and other problems are present.
You do not need to do anything before you have this test.
A test for HIV infection can't be done without your consent. Most doctors offer counseling before and after the test to discuss:
Before the test, it is 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.
The health professional drawing blood will:
You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain (or have only minor discomfort) once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your veins, and your sensitivity to pain.
There is very little risk of complications from having blood drawn from a vein.
A human immunodeficiency virus (HIV) test detects antibodies to HIV or the genetic material (DNA or RNA) of HIV in blood or another type of sample. This determines whether an HIV infection is present (HIV-positive). ELISA results are usually available in 2 to 4 days. Results of the other tests, such as the Western blot or IFA, take 1 to 2 weeks.
No HIV antibodies are found. Normal results are called negative.
If an antibody test is done during the seroconversion period and is negative, repeat testing is needed. Most people have antibodies to HIV within 6 months after becoming infected. If a repeat test at 6 months is negative, there is no infection.
A PCR test to look for genetic material does not detect any RNA or DNA of HIV.
Test results do not clearly show whether a person has an HIV infection. This is usually called an indeterminate result. It may occur before HIV antibodies develop or when some other type of antibody is interfering with the results. If this occurs, a PCR test, which detects HIV RNA or DNA, may be done to see if the virus is present.
A person who still has indeterminate results for 6 months or longer is called "stable indeterminate" and is not considered to be infected with HIV.
HIV antibodies are found. These results are called positive.
A positive ELISA is repeated using the same blood sample. If two or more ELISA results are positive, they must be confirmed by a Western blot or IFA test.
A PCR test finds genetic material (RNA or DNA) of HIV.
Reasons you may not be able to have the test or why the results may not be helpful include:
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
- U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2011). Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Available online: http://www.aidsinfo.nih.gov/ContentFiles/AdultandAdolescentGL.pdf.
- U.S. Preventive Services Task Force (2005, amended 2007). Screening for HIV: U.S. Preventive Services Task Force recommendation statement. Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspshivi.htm.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||Peter Shalit, MD, PhD - Internal Medicine|
|Last Revised||November 7, 2012|
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