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The influence of PrEP on HIV testing


Dear helpline,

Two months ago I started using PrEP. Four weeks before starting with PrEP I had a minor HIV risk. 3,5 weeks after this risk I was tested with a PCR HIV test and a few days later (4 weeks after the risk) I was tested with a 4th generation HIV test again, both to make sure I wasn't HIV positive before starting with PrEP. Both tests were negative, so I started with the PrEP. Were these tests a good indication of my status?

A month after starting with PrEP I was again tested with a 4th generation HIV test, which also came back negative. Now my question is whether the PrEP could influence the test results of this HIV test. If the initial tests before starting with PrEP were conclusive this doesn't really matter of course, but if they weren't I was wondering if the result of my last test could be a false negative. My health care provider says PrEP doesn't influence HIV testing, but I just wanted to be sure. Thanks in advance!

Kind regards,




Thank you for contacting the AIDS Vancouver Helpline as your source for HIV/AIDS related information.

First, I am glad to hear that you are on PrEP. PrEP, short for pre-exposure prophylaxis, is a medication given to those who are at a high risk for getting HIV with hopes of preventing any future exposures. PrEP, when taken properly can be 90% effective in preventing sexual transmisisons. However, even with PREP, the use of a condom is recommended to prevent the spread of other diseases such as STI's and herpes.

With all that said, prior to starting PrEP. One has to be tested for HIV to ensure they are HIV negative. Based on the guidelines AIDS Vancouver follows, all HIV tests are considered conclusive at 12 weeks or 3 months after the last high risk exposure. Also, as your doctors said and from the information we have, PrEP does not affect HIV testing times. With this said, your most recent HIV test (from my calculation is 3 months after your exposure) is considered conclusive and you are HIV negative. Please also know that with the use of PrEP, you will be tested for HIV on a routine basis to ensure your status.

I hope this has answered your questions. Please feel free to contact us if you have any more questions. Good luck with the PrEP!

Best wishes,


AIDS Vancouver Online Helpline
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