What Are Tests Used to Detect the HIV Virus?

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By Erik Steel
eHow Contributing Writer

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The tests most commonly used to identify HIV infection actually test for the presence of antibodies to the virus. However, there are also tests available that can screen directly for viral RNA (the virus' genetic code). HIV tests can be carried out using blood, oral fluid or urine. A positive initial test result is always followed up with another, confirmatory test.

Blood and Oral Fluid Tests

Tests carried out on blood or oral fluid to detect HIV antibodies are a form of EIA, or enzyme immunoassay. These tests use a small sample of blood or oral fluid taken from a vein or oral swab, respectively, and take several days to develop a result.

Rapid Tests

Rapid tests can also be done blood and oral fluid samples. These tests reduce the detection of HIV antibodies to about 20 minutes and are as accurate as other enzyme immunoassay tests.

Urine Tests

There are available tests for HIV antibodies found in urine (where the antibodies are found in much lower concentration). However, these tests are somewhat less accurate than other HIV tests.

RNA Tests

Tests that screen directly for viral RNA are available and can detect HIV sooner than other tests (within as little as a week after infection, according to HIVPlusMag.com). However, they are more expensive and less widely used than other tests.

Confirmatory Tests

A positive result on an initial HIV screening test must be confirmed by a more sensitive test like the Western Blot or Indirect Fluorescent Antibody (IFA). The Western Blot is less expensive and more commonly used than the IFA.

Considerations

An HIV antibody screening test will yield a true positive only if the infected person has already seroconverted (developed a detectable level of antibodies). This normally happens within a month after infection, but may take up to six months.