rapid tests vs. ELISA (Dr. Bob's answer!!) - TheBody.com's Bulletin Boards

I asked Dr. Bob a question regarding the reliability of rapid tests compared to the ELISA, because of a couple of posts on here that have had me, and a couple othes, worried... so here you go, ww's, I hope Dr. Bob's answer makes you feel better and gives you confidence in your results, because it did that for me... Here's the question and answer....

False negative test results
Mar 24, 2006
First of all, thanks for the website and all of the wonderful work you do. I had two encounters I've been worried about- one was unprotected vaginal sex several times with someone of unkown status. The second was protected, but the condom broke, and I was "exposed" to him enough to cause concern, also a man of unkown status. I tested negative via the Oraquick fingerstick 5 months after the first encounter and 3 months after the second. On the bulletin boards on this site I have read two different stories from people who tested negative via the rapid test but positive via the ELISA, around the same time and outside of the window period. Now I am TERRIFIED of a false-negative results. Should I be happy with my results or do I have cause for concern? I was under the impression that the rapid tests were just as accurate as the ELISA test, but maybe I'm mistaken? Are false-negative results typical of the rapid tests??

Response from Dr. Frascino

Hello,

There are now four FDA-approved rapid serological tests. The sensitivity and specificity of these tests is consistently greater than 99%. A negative test is a definitive negative, unless the test is performed in the "window period" (first three months post-exposure). A positive test is considered a preliminary positive result and needs to be confirmed with a Western Blot or IFA.

Turning specifically to the OraQuick test, the sensitivity is 99.6% and the specificity is 99.8%.

Are false-negative results typical of rapid tests? No.

Are rapid tests as reliable as ELISA tests? Yes, but the positive predictive value is dependent on HIV prevalence. That just means positive tests need to be confirmed before they can be conclusively deemed positive.

Should you be happy with your results? Yes! Ecstatic might be an even better word! Congratulations! WOO-HOO!

Dr. Bob

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