Question
Is a negative HIV test four weeks after PEP okay?
7 June 2023. Related: All topics, HIV testing, PEP/PEPSE, South 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,
i hope you are doing well. i tested negative 30days, 40 days and 49 days post-pep with Ab/Ag test. I want to know is it conclusive?
Hi Unknown, your test results are conclusive. You do not have HIV.
A combined 4th generation test will be conclusive when taken any day after 42 days from the last dose of PEP.
The difference in the values of 0.15 to 0.16 does not matter. This number does not have any clinical significance. As long as the number is below 0.9 (which shows clinical uncertainty) the result is clear and you do not have HIV.
Hello experts
After risky exposure I took pep on 7th day (my doctor said it will work more than 72 hours) so I completed the full course. Then I took PCR and 4G ag/ab test at 25 days after pep and followed by I took another same test at 45 days after pep. All tests are came negative but the index value is slightly increased 1st test came 0.15 and second one is 0.16. It will increase further. Please respond. Thank you in advance
Hi Rajesh, your test is conclusive and you do not have HIV. This change in index value has no clinical significance.
Testing and transmission: https://i-base.info/qa/factsheets/hiv-transmission-and-testing
Hello doctors,
After risky exposure I took pep on 7th day (My doctor said it will work after 72 hours too) so I complete it then after the last dose I took 4th G antigen antibody test at 25th day & 45th day(80 days from exposure) both are negative. My concern is index value is changed from 0.15 to 0.16 on second test. It will increase further? Should I repeat the test again? I had a symptoms like cold, dry mouth. Thank you in advance
Hi Christoper, your test results are conclusive. You do not have HIV.
For more information about testing please see here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing
Hai josh I took pep after 68 hours from exposure I took it for 30 days and it was not at same time. I took test after 56 days and 88 days. Taking blood from finger tip don’t know what type of test. Results came negative is it conclusive
Hi Andrew, the 4th generation test you did on day 43 after the exposure will have been conclusive. You do not have HIV.
This means your current symptoms are being caused by something else. Please speak with your doctor so they can investigate and treat as appropriate.
Hello Doctors,
I am from Sweden. I had a possible exposure on 15th October. Due to my anxiety and stress, I took three HIV 4th generation test from lab(blood from vein) on 15th day, 30th day and 43rd day from the exposure and one more 3rd generation Insti rapid finger test on 37th day. All came negative. But I am having some symptoms as mouth ulcers currently. Should I do any further testing due to the symptoms appearing? Thanks in advance for your response!
Hi Alessio, it would be very unlikely to now test positive however for the result to be conclusive it does need to be done 42 days after exposure. The result at 40 days will be more than 95% accurate but it can only be certain after 42 days.
For information about testing please see here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing