I would like to start with the thing that I am on PreP and taking it every day. 3 weeks ago or maybe a bit less I had unprotected sex and starting from Saturday (4th day today) I've been having a severe headache that never had before and some fever not higher though than 37.8C.
I am on painkillers right now and I would say it works quite alright. I tested my blood for HIV by HIV DUO Quick HIV1/HIV2 BIOMERIEUX yesterday and got results to be negative today. I asked the consultant about my situation taking into consideration the fever and severe headache whether it's confirmed that these symptoms were not caused by the conversion just by smth else since I believe that if someone has a conversion going on in their bodies with above-mentioned symptoms it means that a viral load is high and it would be easily detected by the machine. The consultant asked me to contact my doctor since he was not sure about that. I am out of the country now and I've got no possibility to do so. Could you please help me with that?
P.S. I stopped taking PreP on Saturday, the day I felt bad.
Hello and thank you for contacting the AIDS Vancouver helpline.
I understand that you are asking about the accuracy of a point of care (rapid) HIV test performed at approximately 3 weeks after having unprotected sex.
Unprotected anal or vaginal sex is considered to be a high-risk activity for the transmission of HIV. PrEP is a relatively new method for preventing HIV infection, and is not meant to replace other strategies for preventing HIV transmission, such as condoms.
The window period for a point of care (rapid) test is estimated to be 3 to 4 weeks, meaning that a false negative result is possible before the 3 week mark.
It is recommended that you have a 4th generation EIA test performed by a medical professional. The 4th generation EIA test has an estimated window period of 2 to 3 weeks. Canadian testing guidelines recommend re-testing with any HIV test at 3 months (12 weeks). BC government guideline states the following: "Most patients can be tested at 4 weeks following exposure (>95% of infected individuals will have detectable antibodies at this time). If negative, repeat testing at 3 months is recommended (>99% of infected individuals will have a positive EIA at this time)." 
Please refer to table 3-1 on page 13 of the link below in "additional resources" for the window period.
Regards, AIDS Vancouver Helpline/Online, Dyson
- HIV Testing Guidelines for the Province of British Columbia [Internet]. Www2.gov.bc.ca. 2018 [cited 27 August 2018]. Available from: https://www2.gov.bc.ca/assets/gov/health/about-bc-s-health-care-system/office-of-the-provincial-health-officer/hiv-testing-guidelines-bc.pdf