An HIV infection is diagnosed by testing for signs of the HIV virus. Tests are readily available, sometimes free of charge, and are usually done at a clinic or hospital.

There are currently no FDA approved HIV home testing kits; however, the “Home Access HIV-1 Test System” and the “Home Access Express HIV-1 Test System”, made by Home Access Health Corp., allow users to collect samples at home and mail them to approved clinics. These “home access” tests only detect HIV-1, the most common strain of the human immunodeficiency virus.

There are several different kinds of HIV tests, each with its advantages and disadvantages. Most tests look for antibodies, proteins made by the immune system to help identify and fight bacteria and viruses.

With HIV, antibodies are usually detectable starting two to eight weeks after infection, although in rare cases antibodies are not seen for up to six months. This period of time after infection but before HIV is detectable is known as the “window period.” As a result, doctors recommend waiting at least two weeks after exposure for accurate HIV testing; negative results should be confirmed by a second test after about three months.

Note that during the window period when antibodies are not detectable yet, an HIV-infected person is still contagious, even though an HIV test is negative. Anyone exposed to HIV should refrain from sexual activity, or use appropriate safety precautions (such as condoms or dental dams), until the window period has passed, and an HIV test has confirmed a negative result.

The following are tests used to detect the HIV-1 virus. These methods can also be used to test for the HIV-2 virus (which is primarily found in West Africa and affiliated countries), but such testing is usually restricted to at-risk populations, such as immigrants from HIV-2 prevalent countries, or if an HIV-1 test is indeterminate or positive.

*Period of time after infection before HIV is detectable. Example: EIA tests do not give accurate results until at least two to eight weeks post infection.

EIA/ELISA: This is the most common test for HIV infection. EIA (or ELISA) stands for enzyme immunoassay (or enzyme-linked immunosorbent assay). This test looks for antibodies to the HIV virus in blood, urine, or an oral swab. EIAs are very sensitive and can give false positive results. Because of this, EIA tests are usually run twice, and a positive test result will be confirmed using another type of HIV test. Results of an EIA test can be expected within a few days.

Rapid HIV Tests: Like EIAs, rapid HIV tests look for HIV antibodies, but give results as quickly as 20 minutes. Also like EIAs, rapid test results need to be confirmed using another method, such as the Western blot (below).

Western Blot: Western blots are used to confirm a positive EIA or rapid test result. Western blots also look for HIV antibodies. If both an EIA or rapid HIV test and a Western blot are positive for HIV antibodies, a diagnosis of positive HIV infection is declared.

IFA: An IFA (immunofluorescent assay) is an alternative to a Western blot, but serves the same purpose. It also detects HIV antibodies in infected samples and is used to confirm a positive EIA or rapid HIV test result. IFA is more expensive and less commonly used than a Western blot.

RNA Test: RNA tests detect the HIV virus directly by looking for its genetic material, ribonucleic acids (RNA). RNA tests are expensive and rarely used, but can detect the HIV virus in as little as nine to 11 days after infection.

Treatment Overview »