Blood donor has false positive HIV test result — What does this mean?

Originally Published: June 6, 1997 - Last Updated / Reviewed On: July 5, 2012
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Dear Alice,

As a blood donor I got the following notice following a blood donation:

"...At the time of your donation, your blood reacted in a screening test for the antibody to the human immunodeficiency virus type 2 (anti-HIV-2). It is known that false positive results due to factors unrelated to exposure to the HIV virus are common with this test. False positives can be caused by antibodies to viruses other than HIV, antibodies produced by pregnancy, and other medical conditions. Additional studies using other test methods (Western Blot confirmation) failed to confirm the presence of HIV-2 in your blood.... Please note that this result DOES NOT indicate that you are infected with the AIDS virus, nor does it indicate a condition of significant risk to your health..."

What does this mean?? Should I be worried and will I ever be able to give blood again? My lifestyle is low risk (faithfully married for 25 years, no drug use, feel good, etc.). What do you think?

Thanks!

Dear Reader,

Fortunately, the letter that you received indicated that the initial test for HIV antibodies was a false positive. This means that the test wrongly showed that your blood was infected with HIV, when in fact, it was not. Should a person receive a test result that indicates that s/he is HIV positive, it is important to have a follow-up test to verify those results.

Various factors are thought to contribute to a false positive HIV test, including:

  • Antibody cross-reactivity: variousforeign antigens and infectious agents produce antibodies that non specifically cross react with antigens in some HIV test kits. These antigens include cytomegalovirus, hepatitis A and B, giardia, gonorrhea, and mycobactera.
  • Vaccinations: recent influenza and bepatitis B vaccinations are associated with false positive HIV tests. This is because these vaccines can stimulate the production of cross-reacting antibodies.
  • Pregnancy: false positives during pregnancy are mostly attributed to supposed HIV specific antigens, all of which are found in healthy human placenta.

The Western Blot is a confirmatory test, usually done as the second level of screening for an initial HIV positive result. Given that your blood tested HIV-negative on the western blot, this means that your initial test was a false positive. If you need more peace of mind, you may want to get retested just in case. HIV tests are anonymous and free at many clinics and health departments. The National AIDS Hotline [(800) 342-AIDS] may be able to inform you of a site near you. In addition, if you are a Columbia student, GHAP offers free and confidential HIV tests.  

By the way, it is also possible for test results to indicate a false negative. When this happens on an HIV test, the results wrongly show that a person is HIV negative when they are actually positive. This is one reason why it is recommended to routinely test for HIV if a person is higher risk for contracting the virus.

For more information on HIV testing, you can check out the related questions and/or call the GMHC Helpline at (800) 243-7692.

Alice