Talking about home testing for HIV

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How sensitive at 18 days?

I know you have to wait 3 months for a conclusive result but how accurate would a biosure test be 18 days after exposure. Or at least what percentage of people would test positive within 18 days from exposure? Surely these tests are very sensitive?

Other Posts by Gman in this Story

Pep delay? Testing
 on 30th November 2019

I was prescribed pep after an exposure, I have now completed the 28 day course and tested negative 14 days after the pep finished (42 days since exposure). I have read that pep can delay seroconversion if it was not able to successfully abort infection. When is the soonest biosure would pick up a positive result after pep?
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How sensitive at 18 days?
 on 21st November 2017

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3 Responses

Gary Carpenter, BioSure (UK) Limited
 Work on 22nd November 2017

Hi Gman Yes, we will always tend to the conservative side and for good reason. A false negative test result is the worst outcome from any test. A negative test result is always encouraging but if taken less than 3 months from possible infection should be viewed with caution. I hope that helps. Kindest Gary Carpenter BioSure (UK) Limited

 Used on 21st November 2017

Hi Gary. Thanks for the response. It sounds like there's at least some form of encouragement with a negative post 18 day test? Although it be far from conclusive. Would I be right in saying that all antibody detection timeliness would be on the rather conservative side as the biggest disaster would be a false negative? Therefore guidelines would gravitate more to the safe side rather then say early detection of antibody is quite possible (the tests probably show correct results in a much shorter window period but the guidelines need to be conservative to avoid or make sure there are no false negatives?)

Gary Carpenter, BioSure (UK) Limited
 Work on 21st November 2017

Hi G Thanks for getting in touch with us. Unfortunately, the time limit for early detection has little to do with how sensitive the test is. The device looks for antibodies to HIV rather than HIV itself and this is why there is a detection delay. There is a very large variation in the time point at which different people create the antibodies. Some make them after 3 weeks, unfortunately some not until 12 weeks after infection. At 18 days post infection less than 20% of people will have the antibodies. So regardless of how sensitive the test is, the test can't detect something that isn't there. I hope that this helps. Kind regards Gary Carpenter BioSure (UK) Limited

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