On Mar. 2, 1985, the U.S. Food and Drug Administration (FDA) announced the approval of the Abbott first antibody test kit to screen blood donors for HIV-1, the virus that was responsible for the vast majority of AIDS cases in the U.S. The test was designed to screen blood products, not to diagnose AIDS.

The first-generation assays detected IgG antibody and became positive 6 to 12 weeks postinfection. False-positive results occurred, and, a two-test algorithm was developed using a Western blot or immunofluorescence test as a confirmatory procedure.

The second-generation HIV test added recombinant antigens, and the third-generation HIV tests included IgM detection, reducing the test-negative window to approximately 3 weeks postinfection. Fourth- and fifth-generation HIV assays added p24 antigen detection to the screening assay, reducing the test-negative window to 11 to 14 days.

A new algorithm addressed the fourth-generation assay’s ability to detect both antibody and antigen and yet not differentiate between them. The fifth-generation HIV assay provides separate antigen and antibody results and will require yet another algorithm.

HIV infection may now be detected approximately 2 weeks postexposure, with a reduced number of false-positive results.