False Positive HIV Test

Dear Ask The Doctor: My son has donated blood twice and each time received a false-positive HIV test and is now no longer able to donate. I understand that HIV is not something we need to worry about, by something is causing the antibody test to show positive and we're concerned about what that might be. What should we ask of our Doctor when we see her next - are there other tests that might help pin-point what might be causing this? The only thing I can think that might be causing it that we both are prone to fever blisters.

Dear Shannon: There are very few tests in medicine that are 100% accurate.  The accuracy of current HIV testing is improving almost yearly and the best estimates indicate the current false positive test rate for HIV testing is 0.25%.

This would mean 1 in 400 people would have a false positive test when looking at the general population as a whole.  The odds of testing false positive twice would be 1 in 1600 .... not an improbable number.

This does not indicate anything is wrong with your son.  It only indicates he the 1 in 1600 individuals who experience two false positive tests.

I would not be concerned about this and your doctor would likely not feel a need to investigate further.