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UNPROTECTED SEX BUT TOOK PEP AND TESTED NEGATIVE

Question: 

I had unprotected sex with a girl i met but i went for HIV testing with her after sex and we were both negative. Even though we were both negative i took PEP. i also believed her when she told me she last had sex months before that and it was safe sex because she did not hesitate to go for HIV testing. after PEP i took an HIV test 9 days after PEP and it was negative. My worry is that is it possible for the results to change since the guidlines say its suppose to be 3 weeks, 6 weeks and 3 months after PEP? if PEP did not work can the results show positive immediately after PEP? Am really getting worried. please help

i am sick and worried because i have developed some flu and throat infection and was given some antibiotic. later on i developed some fungal infection in the mouth and i read somewhere and it said its an early symptom of HIV. i don't know if its because of antibiotics or not. i contacted that girl again so that we go for HIV testing and we agreed that i pay her if she is negative since am troubling her which also gives me comfort because she is sure she is still negative. what can be the cause of my infection? am i sick?

Answer: 

Hello and thank you for your inquiry.

We gather that you are asking about the accuracy of an HIV test you had nine days after receiving PEP, in response to an incident of unprotected vaginal sex. Unprotected vaginal sex is categorized as a High Risk activity for transmission of HIV. High risk activities are those which present a potential for HIV transmission because they involve an exchange of body fluids, and a significant number of scientific studies have repeatedly associated these activities with HIV. You do not mention how long after the encounter you initiated PEP, or whether you received a full 28 day course of PEP.

Although unprotected vaginal sex is considered to be a high-risk activity for transmission of HIV, based on guidelines here in British Columbia, PEP was not indicated in this instance, due to the fact that your partner tested negative when you were tested together (this test can be considered the baseline test). If the source person’s baseline HIV test is negative, prophylaxis is not required. Investigation of whether a source patient might be in the window period is unnecessary for determining whether HIV PEP is indicated unless acute retroviral syndrome is clinically suspected.(1) From what you described, it sounds like you have no reason to suspect that your partner is HIV positive.

If you had an HIV exposure, and then received a 28 day course of PEP following the exposure, your window period for testing would begin at the end of your PEP course. This is why antigen/antibody testing is recommended at 3 weeks, 6 weeks, and 3 months after completion of PEP. (1)

Fourth-generation HIV tests can detect HIV infection in 50% of people by 18 days after infection; 95% of people by 34 days after infection; and 99% of people by one and a half months after infection. (2) At six weeks, fourth-generation HIV tests have a sensitivity of about 99.9%. In other words, if 1000 HIV-positive people were tested for HIV, 999 would test positive and one would incorrectly test negative. Since the vast majority of people who get tested for HIV are actually HIV negative, the chance of a negative result being false is extremely low. (2) Canadian testing guidelines recommend re-testing with any HIV test at 3 months.

PEP is effective in preventing HIV infection when it’s taken correctly, but it’s not 100% effective. The sooner you start PEP after a possible HIV exposure, the better. While taking PEP, it’s important to keep using other HIV prevention methods, such as using condoms with sex partners.

I am not qualified to diagnose the cause of your throat infection. The symptoms you have described could be linked to many different causes, and can only be attributed to HIV if you receive a positive test result.

Recommendation: Refer to your doctor for HIV testing, specifically at six weeks post completion of PEP and with a 4th generation ab/ag test if available.

Regards, AIDS Vancouver Helpline Volunteer, Dyson