Human immunodeficiency virus (HIV) is a retrovirus that progressively destroys CD4+ lymphocytes, making the body susceptible to attack by foreign infectious agents and numerous forms of cancer. HIV infection is tested via enzyme-linked immunosorbent essay ( ELISA) and western blot test. According to Goaskalice.com, a Columbia University student health website, about 0.2 percent of ELISA tests give positive results that are then proven false by the western blot test. An ELISA test can be falsely positive for several reasons, including a patient's autoimmune disease, multiple pregnancies, blood transfusions, liver diseases, parental substance abuse, hemodialysis, or vaccinations for Hepatitis B, rabies or influenza. Any of these conditions can stimulate the immune system to produce antibodies that cross-react with HIV antigens and produce a false positive.
Antibody Cross Reactivity
It is important to note that HIV antibody tests such as ELISA and EIA do not actually detect the HIV virus, but rather antibodies believed to interact with HIV-specific protein. Consequently, HIV antibody tests can easily produce false positives because a wide range of virus and bacteria---such as tuberculosis, malaria and hepatitis---induce the production of anti-HLA-DR antibodies that can react with HIV and consequently the HIV antigens on the ELISA assay. According to Africa.upenn.edu, HIV tests are notoriously unreliable in Africa. A 1994 study published in the "Journal of Infectious Diseases" concluded that HIV tests were useless in central Africa, where the microbes responsible for tuberculosis, malaria and leprosy were so prevalent that they registered over 70 percent false positive results.
Vaccination
According to Reducetheburden.org, a case control study of 101 blood donors who had been vaccinated against influenza and 191 matched controls showed that recent inoculation with any brand of influenza vaccine was significantly associated with a false positive screening assay for HIV antibodies. Guidelines of both Johns Hopkins Medicine and the New York State Department of Health list influenza vaccination as a known cause of indeterminate results on western blotting for HIV antibodies. Hepatitis B vaccination and other immunizations could lead to a false positive test because of HIV tests are known to cross react with non-HIV antibodies such as HLA.
Pregnancy
During pregnancy, the immune system produces human leukocyte auto antibodies, which cross react with supposed HIV specific antigens on the ELISA assay. Additionally, studies have found HIV protein antigens gp120, gp 24 and p17 in normal human placenta. Furthermore, p24 antigen is localized on HLA positive cells further explaining the significant number of false positive HIV test results in pregnant women.
