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HIV/AIDS testing
Last reviewed: 05.07.2025
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Antibodies to HIV 1/2 are normally absent in the blood serum.
HIV infection is a disease caused by the human immunodeficiency virus (HIV), which persists for a long time in lymphocytes, macrophages, and nervous tissue cells, resulting in slowly progressive damage to the body's immune and nervous systems, manifested by secondary infections, tumors, subacute encephalitis, and other pathological changes.
The causative agents are human immunodeficiency viruses of types 1 and 2 - HIV-1, HIV-2 (HIV-I, HIV-2, Human Immunodeficiency Virus, types I, II) - belong to the family of retroviruses, a subfamily of slow viruses. Virions are spherical particles with a diameter of 100-140 nm. The viral particle has an outer phospholipid membrane, including glycoproteins (structural proteins) with a certain molecular weight measured in kilodaltons. In HIV-1 these are gp 160, gp 120, gp 41. The inner membrane of the virus, covering the core, is also represented by proteins with a known molecular weight - p17, p24, p55 (HIV-2 contains gp 140, gp 105, gp 36, p16, p25, p55).
Detection of antibodies to the human immunodeficiency virus using HIV testing is the main method of laboratory diagnostics of HIV infection. The method is based on ELISA (sensitivity - over 99.5%, specificity - over 99.8%). Antibodies to HIV appear in 90-95% of infected people within 3 months after infection, in 5-9% - after 6 months, in 0.5-1% - at a later date. At the AIDS stage, the number of antibodies can decrease up to complete disappearance. If a positive answer is received (detection of antibodies to HIV), in order to avoid false positive results, the test must be repeated one or two more times, preferably using a diagnosticum of a different series. The result is considered positive if antibodies are clearly detected in both tests out of two or in two tests out of three.
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