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Confusion about post PEP testing

Question: 

Hello,

I had unprotected sex with a sex worker.after 4 days I was placed on 30 days PEP (Yes, I know it is late). I completed the 30 days and 4 weeks post PEP (8.5 weeks post exposure) I had 2 Rapid finger prick tests. Both came back Negative.

1. I was wondering if PEP has any chance at working after 3 days ?
2. What are the chances of it interfering with an antibody test at 8 weeks post exposure ?

Thanks for your time

Answer: 

Hello,

Thank you for your inquiry. From what we gather from the question, you were asking about the efficacy of post-exposure prophylaxis (PEP) started 4 days after engaging in unprotected sex as well as the conclusiveness of two negative rapid finger prick HIV tests conducted 4 weeks after a full prescription of PEP was completed. From the information given, this scenario is determined to be High Risk (evidence of transmission through these activities and is the majority of cases of transmission).

The scenario mentioned above does meet the three components of the Transmission Equation. It was very responsible of you to seek out PEP after a risky exposure, but unfortunately if PEP is started more than 72 hours after the exposure it has little to no effect on preventing a possible HIV transmission (1). The earlier PEP is started after a possible HIV exposure, the better it is at preventing an HIV infection since it can stop the virus from getting into your cells and making more of itself.

In regards to the testing you received, the negative results from the rapid finger prick HIV tests are reassuring, but they are not conclusive 4 weeks after PEP completion. These type of tests depend on the detection of antibodies to HIV, which are reliably detectable (if present) 12 weeks post-exposure (or post-PEP). More testing should be conducted 12 weeks post-PEP for completely conclusive results.

Recommendation: Refer to a physician for an HIV test 12 weeks post-PEP for completely conclusive results.

Regards, AIDS Vancouver Helpline/Online, Marie