Confirmation Tests

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.