Hi,

I had a blood test done (I believe thats the western blot) a few yrs back that came back positive. My boyfriend was in disbelief so we both got tested with the mouth swab test (I believe thats the Elisa test) and both came back negative. I am very confused and am reluctant to go back to do yet another test. The doctor that performed the later of the tests, the mouth swab, assured us everything is fine but I cant help but think about it. Is one test more accurate? and should I get tested for the third time? As well, I should mention that I have had several TB tests done and they can never tell if I have it until I do an xray...not sure if that effects anything but I thought I'd mention it.

Hello.

The doctor who assured you everything is fine is correct! Whoever ordered the first test, the Western Blot, did so in error! Western Blot tests should only be used to confirm a repeatedly reactive (positive) HIV-antibody screening test, such as an ELISA, EIA or rapid test. Testing with a Western Blot as an initial test can result in a false-positive result, because it is a more "specific" test than the preliminary tests, which are more "sensitive." See link below for a discussion of sensitive versus specific tests.

You shouldn't be fearful or reluctant about retesting. However, you should make sure the proper tests are ordered! Your issues with TB testing would not affect HIV-diagnostic testing results.

Be well.

Dr. Bob

hsv 2 positive hiv false positive (SENSITIVITY VERSUS SPECIFICITY, 2011) Jul 24, 2011