Which lab assays are used to differentiate between HIV-1 and HIV-2 antibodies?

Updated: Jun 23, 2020
  • Author: Philip A Chan, MD, MS; Chief Editor: John Bartlett, MD  more...
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Specimens that react to the antigen/antibody combination immunoassay should undergo confirmatory testing with a different antibody-based immunoassay to differentiate between HIV-1 and HIV-2 antibodies. Since HIV infection is lifelong, positive serology results reflect current rather than cleared infection. If the antibody immunoassay is nonreactive or indeterminate, HIV viral load testing should be performed (this may be either quantitative or qualitative). A positive HIV viral load suggests acute HIV infection. Importantly, viral load tests are usually specific only for HIV-1 infection. If HIV viral load testing is nonreactive and the HIV-1 and HIV-2 antibody immunoassay results are negative or indeterminate, the initial antigen/antibody combination immunoassay result may be false-positive. Repeat testing is warranted, as well as consideration for HIV-2 testing. Individuals in the early stages of HIV infection, including acute infection, typically have higher levels of viremia and a greater risk of HIV transmission. [10, 11, 12]

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