The previous algorithm, consisting of a repeatedly reactive immunoassay for HIV antibodies and positive HIV-1 Western blot or HIV-1 IFA, has been the gold standard for laboratory diagnosis of HIV-1 infection in the United States since 1989. False-positive results from this combination are rare.67 HIV-2 infection remains uncommon in the United States, and no definitive criteria have been recommended for HIV-2 diagnosis.27 Developments and observations in five areas led CDC to update recommendations for the laboratory diagnosis of HIV-1 and HIV-2 infections