HIV is usually diagnosed by testing your blood or a sample of cells taken with a cotton swab from inside your cheek for the presence of antibodies to the virus. Urine samples can also be tested for HIV antibodies, but the results are slightly less accurate.
Unfortunately, these HIV tests aren't accurate immediately after infection because it takes time for your body to produce antibodies to the virus. Most people develop antibodies to the HIV virus within three to six months of infection.
If this test is positive — meaning you have antibodies to HIV — lab technicians run the same test again on the sample you provided. If the repeat test is also positive for HIV antibodies, you need a confirming blood test called the Western blot test, which checks for the presence of HIV proteins.
You receive a diagnosis of HIV only if all three tests are positive. It can take a few days to a few weeks to get the results from all three tests.
Rapid HIV testing
Several rapid tests offer highly accurate information within as little as 20 minutes. These tests also look for antibodies to the virus using a sample of your blood, drawn from a vein or a finger prick, or fluids collected on a treated pad that's rubbed on your upper and lower gums. The oral test is almost as sensitive as the blood test and eliminates the need for drawing blood. A positive reaction on a rapid test requires a confirming blood test.
Home HIV testing
For home testing, you mail in a drop of your blood and then call a toll-free number to receive your results in three to seven business days. This approach ensures your privacy and anonymity — you're identified only by a code number that comes with your kit. You may speak to a counselor before taking the test, while you're waiting for results or after you've received your results.
Early-detection HIV testing
Some tests can detect HIV infection earlier, before antibodies are detectable in standard HIV testing. These early-detection tests evaluate your blood for genetic material from the virus or for proteins that develop within the first few weeks after infection.
Tests that detect HIV infection before you've developed antibodies to the virus may cost more than standard HIV testing and may not be as widely available. You will also still need standard antibody testing later to confirm results because false-positives and false-negatives are possible.
Jan. 06, 2012
- HIV infection: Detection, counseling and referral. Centers for Disease Control and Prevention. http://www.cdc.gov/std/treatment/2010/hiv.htm. Accessed Oct. 17, 2011.
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- p24 antigen. American Association for Clinical Chemistry. http://labtestsonline.org/understanding/analytes/p24/tab/sample. Accessed Oct. 17, 2011.
- Bartlett JG. Diagnostic assays for HIV infection. http://www.uptodate.com/home/index.html. Accessed Oct. 17, 2011.