Description

HIV Antibodies (Confirmation) – Western Blot is a supplemental serological confirmatory test historically used to detect antibodies against Human Immunodeficiency Virus (HIV), especially HIV-1, after a reactive HIV screening test such as ELISA / EIA / HIV Ag-Ab assay. The test works by identifying antibodies to specific HIV viral proteins through protein separation and immunoblotting, helping confirm whether a patient has developed an immune response consistent with HIV infection. Traditionally, HIV Western Blot was widely used as the standard confirmatory test following a positive HIV screening result. However, in modern practice, Western blot is considered an older-generation confirmatory assay and has largely been replaced by HIV-1/HIV-2 antibody differentiation assays and HIV nucleic acid testing (NAT / RNA testing) because Western blot may be less sensitive in early infection, may produce indeterminate results, and may miss acute HIV infection. The CDC and APHL updated HIV diagnostic recommendations state that HIV-1 Western blot is no longer part of the recommended testing algorithm for routine HIV diagnosis. This test may still be encountered in some legacy, academic, or referral settings, but for most modern laboratories, HIV antibody differentiation tests are preferred for confirmation after a reactive screening assay. Results must always be interpreted with the patient’s screening result, exposure history, window period, symptoms, and follow-up nucleic acid testing where indicated. The CDC’s updated recommendations explicitly note that reactive screening specimens should undergo HIV-1/HIV-2 differentiation testing, and if nonreactive or indeterminate, proceed to HIV-1 NAT rather than Western blot.

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