The medical establishment maintains that HIV antibody tests are 99.5 per cent accurate, but new evidence suggests that a startling array of factors can cause false positive results.
These include recent exposure to viral infection, viral vaccines such as flu or hepatitis B, autoimmune diseases like lupus, scleroderma and rheumatoid arthritis, alcoholic hepatitis or liver disease, pregnancy in women who have had children, multiple blood transfusions and the presence of a variety of other antibodies.
According to Christine Johnson from HEAL in Los Angeles, an AIDS group in California, a positive test result depends on what antibodies a person carries and what antigens a particular test kit contains.
"Some, but not all people who have blood transfusions, prior pregnancies or an organ transplant will make HLA antibodies, " she says, "and some, but not all, test kits (both ELISA and Western blot) will be contaminated with HLA antigens to which these antibodies can react."
When these two conditions coincide you might get a false positive due to HLA cross reactivity (Townsend Letter for Docs, December 1998: 26-9).