|False Postitive (FALSE POSITIVE TESTS, SENSITIVITY VERSUS SPECIFICITY, 2010)
Jan 9, 2010
I was tested a few months ago for HIV and other STDS. Everything was great except for my HIV test came back positive with the Elisa tests and my western blot was a negative. I came in a month later and retook the test and my elisa then came back negative. My GP told me that this ment it was a false positive and it can be caused by a bunch of different things being that the Elisa is a very sensitive test. My question to you is, would that assumption be correct. Since I came back a month later and retested with a negative elisa does that mean I can take a deep breath in and relieve all this anxiety? Thank you so much for what you do!
| Response from Dr. Frascino
The assumption is completely accurate and correct. You can relax Max!
Diagnostic HIV screening involves a two-part process. The first test (ELISA or rapid test) is extremely sensitive, so as not to miss any true HIV-positive cases. In fact, it's so sensitive it sometimes picks up some "false positive" cases. (These folks test positive, but are really negative, like you!) Once someone tests ELISA- (or rapid test-) positive, he needs a confirmatory test, such as a Western Blot, which is a more specific test. It can determine "true negatives" more accurately than an ELISA test. For someone to be diagnosed HIV positive, he needs both a positive ELISA (sensitive test) and confirmatory Western Blot (specific test). I know this gets confusing, but ELISA tests can determine more "true positives" and Western Blot tests can determine more "true negatives." A positive ELISA plus a negative Western Blot would technically be considered a negative HIV diagnostic screening! So go ahead and take that deep breath. All is well, including you!
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