On the average, 0.2 percent of ELISA tests give a false positive HIV test result that are then proven incorrect by a Western Blot test, notes Goaskalice.com, the Columbia University student health website. Autoimmune diseases, recent vaccinations, multiple pregnancies or prior infections with hepatitis B, malaria or tuberculosis can stimulate the production of antibodies that cross create with HIV antigens, thus producing a false positive HIV test.
Antibody Cross Reactivity
Individuals placed in the high risk category such as gay males and hemophiliacs are exposed to a plethora of foreign antigens and infectious agents such as cytomegalovirus, hepatitis A and B, giardia, gonorrhea and mycobactera and thus produce antibodies that non specifically cross react with antigens in the HIV test kits, notes Virusmyth.com. ManagingDesire.org, notes that false positive reactions have been reported in 19 percent of people with hemophilia, 13 percent of alcoholic patients with hepatitis, and 4 percent of hemodialysis patients. Furthermore, Africa.Upenn.edu notes a 1994 study published in the "Journal of Infectious Diseases" in which HIV tests were concluded to be useless in Central Africa due to the prevalence of infections such as leprosy, malaria and tuberculosis leading to a 70 percent false positive test due to the cross reactivity of these antibodies to HIV antigens on the ELISA assay.
Flu and Hepatitis B immunizations are known to cause false positive HIV ELISA and Western Blot results. A research study with 101 blood donors vaccinated against the influenza virus and 191 control subjects showed that recent influenza vaccination was highly associated with a false positive HIV test because these vaccines can stimulate the production of cross-reacting antibodies, notes Reducetheburden.org. Furthermore, on the 21st of May, 2010, the Brazilian Ministry of Health released a statement that the H1N1 flu vaccine can cause false positive HIV tests due to the production of IgM antibodies that cross reactive with HIV antigens on the ELISA plate, notes Noticias.terra.com. A false positive HIV result may appear up to 112 days after the flu vaccination.
Pregnancy, particularly multiple pregnancies is also a cause of false positive HIV test results. This is mostly attributed to supposed HIV specific antigens, all of which are found in healthy human placenta. Furthermore, HLA positive cells known to cross reactive with supposed HIV antigen on the ELISA plate also has a significant amount of the p24 antigen localized on them. All of these factors explain the significant rate of false positive HIV tests in pregnant women. Furthermore, Rethinkingaids.com notes a report from the American Medical Association in which the preliminary health department data from August through November 1999 identified 32 pregnant women as HIV positive. After a confirmatory test, 17 of these women were determined to be negative for the HIV virus.