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Epidemiologic data suggest that AIDS is caused by at least 2 types of HIV, HIV-1 and HIV-2. HIV-1 has been isolated from patients with AIDS and asymptomatic infected individuals. The closely related HIV-2 was first isolated from patients in West Africa in 1986, and the first case of AIDS due to HIV-2 in a patient was reported in the United States in 1988. HIV-2 appears to be endemic only in West Africa, but HIV-2 also has been identified in individuals who have lived in West Africa or had sexual relations with individuals from that region. HIV-2 infection is rare in the United States (<100 cases reported to date); most of the reported cases are from the northeastern states and involve persons from West Africa.
Both HIV-1 and HIV-2 are transmitted by sexual contact, sharing contaminated needles, exposure to infected blood or blood products, or from an infected mother to her fetus or infant. During the course of HIV-2 infection, antibodies are formed against the viral proteins p26 and gp34. Immunosuppressed patients may fail to develop these antibodies. At-risk patients with positive results for HIV-1/-2 antigen and antibody combination assays and/or indeterminate or negative results on HIV-1 antibody by Western blot (especially those showing reactivity only with HIV-1 core [p18, p24, or p55] and polymerase [p31, p51, or p66] proteins) should be investigated for the presence of HIV-2 antibodies.
Diagnosis of HIV-2 infection in symptomatic patients with or without risk factors for HIV-2 infection
Reactive screening test results suggest the presence of HIV-2 antibodies. All repeatedly reactive serum specimens that are repeatedly reactive by HIV-2 antibody (EIA) are automatically confirmed by an HIV-2 antibody immunoblot assay with an additional charge. HIV-2 antibody immunoblot results are reported as either Positive, Negative, or Indeterminate.
Negative screen results indicate the absence of HIV-2 antibodies. These results should be interpreted with caution in patients who are at high risk or have symptoms or signs of HIV infection.
This test is not offered as a screening or confirmatory test for blood donor specimens.
This test is not offered for maternal or newborn HIV screening for specimens originating in New York.
All results that are reactive by HIV-2 antibody screening test and positive by confirmatory test should be verified by testing second serum specimens. Positive confirmatory HIV-2 antibody test results are required by statute in most states to be reported to the state departments of health for surveillance of communicable diseases.
False-reactive HIV-2 antibody screening test results may occur in patients with HIV-1 infection due to cross-reactivity of HIV-1 antibodies with the viral core and polymerase proteins used in the HIV-2 screening tests.
Patients at risk for HIV-2 infection and suspected to have acute HIV-2 infection may have a) negative HIV-2 antibody screen results, or b) repeatedly reactive HIV-2 antibody screen results but negative or indeterminate confirmatory test results. For such patients, testing for HIV-2 RNA or proviral DNA (FHV2Q / HIV-2 DNA/RNA Qualitative Real-Time PCR) is recommended.
This assay is not FDA-approved for testing cadaveric or hemolyzed specimens.
Assay performance characteristics have not been established for the following types of serum specimen:
-Presence of particulate matter
See HIV Serologic Interpretive Guide in Special Instructions for further interpretive information.
1. Constantine N: HIV antibody assays-May 2006. HIV InSite Knowledge Base (online textbook); available from URL: http://hivinsite.ucsf.edu/InSite?page=kb-00&doc=kb-02-02-01
2. Branson BM, Handsfield HH, Lampe MA, et al: Centers for Disease Control and Prevention: Revised recommendations for HIV testing of adults, adolescents, and pregnant women in health-care settings. MMWR Morb Mortal Wkly Rep 2006;55(RR14):1-17
3. Hariri S, McKenna MT: Epidemiology of human immunodeficiency virus in the United States. Clin Microbiol Rev 2007;20:478-488
4. Owen SM, Yang C, Spira T, et al: Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States. J Clin Microbiol 2008;46:1588-1595