AIDS Home > Confirmation and Blood Tests for HIV
If the sample repeatedly shows the same result or either duplicate test is reactive, the results are "confirmed" using a second HIV blood test, such as the Western blot. This more specific (and more expensive) test can tell the difference between HIV antibodies and other antibodies that can react to the EIA and cause false-positive results. False-positive EIA results are uncommon, but can occur. A person is considered infected following a repeatedly reactive result from the EIA, confirmed by the Western blot test.
New HIV Blood Tests
In addition to the EIA or ELISA and Western blot, other blood tests for HIV 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.
- Dot-blot immunobinding assay: A rapid-screening blood test that is cost-effective and that may become an alternative to standard EIA and Western blot testing.
- Immunofluorescence assay: A less commonly used confirmatory blood test for HIV used on reactive ELISA samples or when Western blot test results are uncertain.
- Nucleic acid testing: For example, viral RNA or proviral DNA amplification method. A less available blood test that can be used to resolve an initial indeterminate Western blot result in certain situations.
- 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.