There are a number of approved methods for testing for HIV, either by detecting antibodies to the virus or by directly detecting the virus' genetic code. HIV testing is done in two steps; the first test is normally an enzyme immunoassay (EIA or ELISA), while a positive initial result triggers a more sensitive confirmatory test. HIV tests can be conducted on blood, oral fluid or urine.
Blood and Oral Fluid Immunoassays
Blood and oral-fluid EIAs use samples of blood and oral bodily fluids, taken with a needle or an oral swab, respectively, and check for the presence of antibodies to the virus. The results of these tests may take several days. Rapid versions of these tests are also available; these can screen for HIV antibodies in as little as 20 minutes and are as accurate as standard tests. All forms of enzyme immunoassay will only produce a true positive if the tested individual has already seroconverted (developed a detectable level of antibodies to HIV), which happens between one and six months after infection.
Urine Immunoassay
Urine EIAs also test for the presence of HIV antibodies. However, these tests are considered to be less accurate than blood and oral fluid tests.
RNA and DNA Tests
Tests can also be done that directly detect the presence of viral genetic material. HIV DNA tests treat samples with reverse transcriptase to turn viral RNA into DNA and then test for this; these tests are used for children born to HIV-positive mothers. Tests that detect viral RNA are used to screen blood supplies and for other purposes of rapid detection. These tests are useful because they reduce accurate detection to less than two weeks, as they do not rely on the presence of a detectable level of antibodies.
Confirmatory Tests
If a positive result is registered during the first tense, a second, more sensitive test is always done. The most common of these is the Western blot, which, like other tests, checks for the presence of HIV antibodies. A less common and more expensive test called in Indirect Fluorescent Antibody test is also sometimes used.
Tags: presence antibodies, antibodies virus, blood oral, detectable level, detectable level antibodies, enzyme immunoassay