![]() Test results are only considered to support the diagnosis of HIV infection when the screening test results are repeatedly reactive and either supplemental test (ie, HIV-1/2 antibody differentiation or HIV-1 RNA) is positive. The potential adverse effects of a biological false-positive screening test result are ameliorated by use of this CDC-recommended multi-step testing algorithm. A few of the causes hypothesized in the medical literature include recent administration of selected vaccines, presence of HLA-DR antibodies, presence of rheumatoid factors, reactive RPR, hypergammaglobulinemia, cross-reactive immune response to other exogenous and endogenous retroviruses, and autoimmune conditions.Īlthough there are occasional biological false-positive results observed with HIV screening tests, as with all screening tests, the specificities of the FDA-approved HIV screening tests are very high (>99%). The precise reason for a biological false-positive result in any individual specimen is not likely to be definitively known. The CDC recommends using a fourth-generation HIV antigen/antibody test for screening and diagnosis because it can detect HIV during both the acute and chronic phases of infection. Both of these actions reduce the likelihood of transmission to uninfected partners. However, if individuals are diagnosed during the acute phase of the illness, they can be counseled regarding risk-reduction practices and can reduce their viral load with antiviral medication. Individuals with acute HIV infection have much higher viral loads, making them more likely to transmit the virus. Society benefits because actions can be taken to reduce HIV transmission. The patient benefits in that he/she can be more quickly evaluated for administration of appropriate antiviral medications, which may reduce the adverse early impacts of infection. This ability has substantial individual and societal benefits. Thus fourth-generation-based screening tests can detect HIV during a portion of the acute phase and all of the chronic phase of the disease. 4 In contrast, fourth-generation HIV-1/2 testing methods can detect HIV-1 antigen as well as HIV-1 and HIV-2 antibodies. Because third-generation tests detect only antibodies to HIV, they cannot detect HIV infection during acute infection-the period after virus acquisition when viral protein (HIV-1 antigen) may be detectable but antibodies to HIV are not. Third-generation test results are considered repeatedly reactive only after a person has developed detectable levels of antibody in their serum or other body fluid. ![]() HIV antigen/antibody fourth-generation-based screening tests can simultaneously detect both HIV-1 antigen (ie, viral protein) and HIV-1/2 antibodies, whereas HIV-1/2 antibody third-generation-based screening tests detect only antibodies. ![]()
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