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Are there
other tests available?
The EIA (enzyme immunoassay)
is the standard screening test used to detect the presence of
antibodies to HIV. The EIA should be used with a confirmatory
test such as the Western blot. Tests that detect other signs
of HIV are available for special purposes, such as for additional
testing of the blood supply and conducting research. Because
some tests are expensive or require sophisticated equipment and
specialized training, their use is limited. In addition to the
EIA, other tests now available include:
- Radioimmunoprecipitation
assay (RIPA): A confirmatory blood test that may be used when
antibody levels are very low or difficult to detect or when Western
blot test results are uncertain. An expensive test, the RIPA
requires time and expertise to perform.
- Rapid latex agglutination
assay: A simplified, inexpensive blood test that may prove useful
in medically disadvantaged areas where there is a high prevalence
of HIV infection.
- Dot-blot immunobinding
assay: A rapid-screening blood test that is cost-effective and
that may become an alternative to conventional EIA and Western
blot testing.
- p24 antigen capture assay:
Also known as the HIV-1 antigen capture assay. This blood test
was added as an interim measure by the Food and Drug Administration
(FDA) in 1996 to HIV-antibody testing to protect the blood supply
further until other tests become available to detect early HIV
infection before antibodies are fully developed. Because some
activity of p24 antigen is unpredictable, this test is not useful
for helping people find out if they have HIV.
- Polymerase chain reaction
(PCR): A specialized blood test that looks for HIV genetic information.
Although expensive and labor-intensive, the test can detect the
virus even in someone only recently infected. To further protect
the blood supply, the FDA has indicated that the development
and implementation of tests for HIV genetic material such as
PCR is warranted.
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