Question
Is a negative HIV test four weeks after PEP okay?
7 June 2023. Related: All topics, HIV testing, PEP/PEPSE, Southern Africa.
Good day.
Is it possible to test positive after testing negative after completing 28 day of PEP?
Answer
Hi
In the UK, people need to wait 4 to 6 weeks after the last dose of PEP before taking a 4th generation HIV antigen/antibody test.
If this test is negative after 6 weeks, then someone is told they do not have HIV. If it is negative after 4 weeks, it means HIV is unlikely, but that a second test should confirm this after a few more weeks.
There is no point taking an HIV test as soon as you finish PEP.
This is because the PEP could just be covering up or delaying a potential infection.
This answer was updated in June 2023 from a question first posted in November 2020. This is because UK guidelines now recommend testing after 6 weeks rather than after 4 weeks.
Hi,
After completing PEP, the standard 4th Generation antigen-antibody test may not detect HIV-2 within the 45 days window period. Is it advisable to wait for 3 to 6 months before testing for HIV-2?
Hi Luca, I am sorry to hear how unwell you have been feeling for the last 2 months. Have you spoken to a doctor and had any investigations/treatment?
A 4th generation test is conclusive after 42 days. Testing at 50 days after PEP will confirm your status. PCR is not used to confirm status. This is because it can be affected by other infections and not reliable to confirm HIV.
A positive antibody test is required to start treatment.
Hi, I’m asking for a consultation, I’ve been very ill for 2 months, I’ve finished my pep, I’ve started to have itching, generalized lymphadenopathy (including the neck), blisters that appear and disappear within a day, fatigue, mental confusion, muscle pain and joints, and finally I have 4/5 10^9 u/l of white blood cells, with a slight lack of neutrophils
I most likely have HIV. I wanted to understand the reliability of a 4th generation test 50 days after the end of the PEP, even if given the circumstances I believe it is quite low, and in conclusion whether a NAT PCR would be sufficient to start the therapy without having antibodies.
Hi Sharma, your test results are conclusive. You do not have HIV and do not require any further tests.
For information about testing please see here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing
Hello,
After exposure I initiated pep on 8 th day and took hiv 4 generation ag ab test after 44 days post pep and 78 days after exposure. Is it conclusive or do I need to take another test? Late pep will affect the hiv test?
Hi L, for information about testing please see here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing
Hello super anxious l. I got in touch with a HIV charity who advised me a 4th gen test would be quite accurate 3 weeks after finishing pep. Especially since I had a low risk encounter I should try and calm down and a negative test would be pretty accurate. Do you think this is true? A negative 4th gen anti body test would be pretty accurate 3 weeks after pep completion
Hi Gianni, a 4th gen combo test 4 28 days after the last dose of PEP is 95% accurate.
Hi doctor, how accurate is an HIV 4th gen combo test 28 days after the last dose of PEP (56 days after exposure)? I tested negative, I know it’s not considered conclusive yet, can I spend these two weeks before a definitive test with a lot of peace of mind? is there a chance it will turn positive?
Hi Alessio, yes your result is conclusive. You do not have HIV and no further tests are needed.
More information about testing can be found here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing