Principles and Procedures of Human Immunodeficiency Virus Serodiagnosis

An important early impetus for the development and testing of serologic methods to detect human immunodeficiency virus (HIV) infection was the need to guarantee the safety of the blood supply. A quick review of the statistics provided in this chapter makes clear the need for the continued development of serologic methods, including point-of-care testing, that are useful especially in resource-poor settings. The standard screening tests for HIV infection involve detection of HIV-specific antibodies. The enzyme-linked immunosorbent assay (ELISA) is the standard screening test for HIV-1 infection. Individuals with indeterminate or positive ELISA results should undergo confirmation testing (generally by Western blotting [immunoblotting]) to determine if the reactivity is primarily directed to HIV-1 infection or secondarily directed to cross-reacting antibodies. It has now become the standard practice in blood banks to screen donated blood samples with one of the new HIV-1-HIV-2 combination ELISAs. The major core protein of HIV-1 is p24. The assay to detect the p24 antigen has been used for many years in the prognostic staging and management of infected individuals and is licensed in the United States as part of routine blood donor screening. Serologic assays to detect antibodies to HIV are the most widely used means of laboratory diagnosis of HIV infection. Most HIV testing algorithms include an ELISA as the screening component and Western blotting as the confirmatory method.