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When to test for HIV during and after completion of PEP

I get this question a lot.

First of all, data on this is lacking and very hard to come by.

There are many theories that hypothesize that PEP reduces viral replication and delays sero-conversion and therefore make HIV testing less accurate. These theories have neither been proven nor debunked.

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Furthermore, there is very limited data on the use of P24 antigen tests (including Combo/Duo tests) and viral load testing for diagnostic purposes in patient who have or undergoing PEP. In fact, studies on monkeys (and more limited studies on humans) have shown positive viral load tests in individuals who were subsequently found not to be infected. This could represent an aborted infection (which is what PEP is supposed to and designed to do) rather than a true false positive. This illustrates one of the limitations of using viral load tests to diagnose people currently on or have completed PEP.

Official Guidelines

The US CDC Guidelines on Antiretroviral Postexposure Prophylaxis After Sexual, Injection-Drug Use, or Other Nonoccupational Exposure to HIV in the United States recommends that patients should be tested for the presence of HIV antibodies at baseline, 4 – 6 weeks, 3 months and 6 months post exposure.

The Joint WHO/ILO guidelines on post-exposure prophylaxis (PEP) to prevent HIV infection recommends HIV testing at baseline, immediately after completing PEP (i.e. 4 to 6 weeks post exposure) and again ‘3 – 6 months post exposure’.

The 2 guidelines are rather similar although the US CDC seems to be more firm on the requirement of a test at 6 months compared to the WHO guidelines.

Very recently, the New York State Department of Health AIDS Institute’s adult HIV guidelines committee undertook a comprehensive re-evaluation of its HIV occupational PEP guidelines and issued some changes which included shortening of the time of HIV testing after exposure to 3 months if modern, blood based, standard HIV testing is performed. This is certainly promising however it refers to occupational HIV exposure only and the same data and recommendation may not be extended to non-occupational exposure.

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Summary

 In short, most official guidelines still recommend testing at 6 months for patients who have undergone PEP.

Sometimes testing at 3 months post exposure is good enough but this really depends on what kind of test is done.

My own experience is the test done at 4 weeks exposure (or immediately upon completion of the PEP medications) is very indicative. I will still recommend a retest at 3 months although I have yet to see the test at 4 weeks get it wrong.

At the end of the day, the best person to advise you is still the doctor who prescribed you the PEP. He/She will be most familiar with the sensitivity of local tests available and the local guidelines.

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Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.

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931 Comments

  1. Kayman

    Dr doctors, please help. I got exposed on the 30th of March this year, a week later a started having body torment , itchy face, swollen lymph nodes and mouth discomfort. A doctor gave me pep which I took for 30days. But my symptoms continued as I had all symptoms associated with ars. I tested at baseline which was negative(the instant test) I did also at six weeks, still negative. I have thrush,nodes and dry mouth. Is 6weeks post pep test and 12weeks post exposure conclusive( with a fourth generation test )as a result of my symptoms. I am really worried.Thanks

  2. BeyondIt

    Hi Doctor

    After unprotected vaginal intercourse, I took PEP at 67.5 hours and tested 29, 30, 41, 49, 58, 70, 72, 84, 114 days (84 days after PEP completion), all negative on 4th generation tests. The exposure was on January 23, 2018 and the last test was on May 17, 2018.

    However, around June 9 or 10, 2018, I recently had headache, dizziness, due mostly to water inside head after a wash, runny nose, cold, mild fever for two days.

    Two days after all of them were gone, I had night sweats with a soaked shirt. This was yesterday. Meanwhile, I was unnecessarily scared that while giving me Tetanus Toxoid, they reused a syringe, as I didn’t see them unpack. This was on day 72 and day 114 was negative, with 42 days in between.

    Am I all clear? Can I move on? Are these results conclusive? Can I have unprotected sex with any new partner, like say if I am going to get married or in a marriage? Can I put this all behind and move on?

    The more time goes, the more I am scared and some say six months is conclusive after PEP, which adds to our anxiety. Is 6 months test required? I am scared because of what some doctors say. Is it required? Or no? Please reply. Thank you

    • I would consider your tests conclusive. Move on with your life.

      • BeyondIt

        Wow! Thanks Dr. Jon, so can I find someone to marry and even have unprotected sex in monogamous relationships? I promise this is all I want to know, as I worry about disclosures now.

  3. Please help Doctor.

    My condom broke on 2/17 with a sex worker from the Dominican Republic. I live in the United States. I started pep (truvada and issentress) 68 hours later (I know it’s late).

    On 3/13, the third week of PEP, I had a fever for 2 days with no mucous. I also had various symptoms pop up like fatigue, diahrrea, sore throat, slight cough, headache, slight joint aches for 4 days around the time of the fever. I thought I was seroconverting or some of it was caused by the PEP. But PEP doesn’t cause fever. I also got blood work done by the emergency room, and compared the results to my visit to get the PEP on 2/20. My lymphocyte levels dropped dramatically in 3 weeks (all the way to 12%). I’ve read various articles that say low lymphocyte levels without a change in anything else on your blood test is a potential sign of a viral infection, or HIV. I’m so scared. I’m usually someone that rarely gets sick.

    on 3/15, 26 days after exposure (23 days since beginning PEP, but still on PEP), I was negative using a fourth generation rapid test.

    On 3/21 I finished PEP. On 3/25 I tested negative for a second generation rapid blood test.

    From 3/28 to 4/2 I had a slight headache everyday.

    on 4/15, I started getting a fever again. This time the fever lasted a whole week, with no mucous again. This is 25 days after PEP ended. I thought I was seroconverting after PEP. I had a lost of appetite some days, and it felt the same as last month’s illness but less severe. However, the fever lasted for a whole week this time instead of 2 days, but it was a mild fever.

    4/22, 32 days after PEP ended, I took an at home oraquick test and it was negative. I also took the second generation blood finger prick test again and it was negative.

    5/5, 6 weeks and 3 days (45 days) after PEP ended, I took an at home oraquick test again and it was negative.

    5/18, 8 weeks, 2 days after PEP (58 days after PEP), I tested negative on Oraquick again.

    5/20, 8 weeks, 4 days after PEP (60 days after PEP), I tested negative on second generation rapid test again.

    How conclusive is this result? Given my symptoms, especially the low lymphocyte levels and fever, late PEP, etc.

    • I would consider your results essentially conclusive, however I would recommend a 4th generation test rather than 2nd or 3rd generation if you wish to have conclusive results before 3 months exposure.

      • Please help Doctor.

        5/22, 62 days after PEP (8 weeks, 6 days), I tested negative on a fourth generation lab test!!!! I also took a rna test on the same day, but it takes a week for the results to come back. Is there any chance the rna (nat) test will come back positive?

  4. Hi Doc,
    Good day. I had a 4th generation duo test done at 54 days post exposure (24 days after completion of PEP) and it was negative Can I consider this to be conclusive?

    Thanks

    • Dr. Julian Ng

      Hi,

      Yes, I would consider your results as conclusive. If you are still concerned, you may wish to repeat 3 months post-exposure.

  5. I had a 3rd generation blood finger prick test done today, 4 weeks after pep. Is this enough? It was negative. I have been suffering from a mild fever this whole week. I’m concerned. When should I do another round of testing?

    • Dr. Julian Ng

      Hi,

      My suggestion is to repeat after 3 months if you are still concerned.

      • Thank you doctor. Is there any evidence that using a blood, finger prick test is less accurate than a regular blood test? My test was actually 32 days after completion of PEP. I’ve been having a fever and slight sore throat for a week. This is the longest I’ve ever had a fever, and it coincided exactly 3 weeks after finishing pep so I thought I could be seroconverting late.

        • Dr. Julian Ng

          Hi,

          Not really. The HIV tests are initial screening test which if tested positive will require further confirmation. However, if they are negative and they are past the window period indicated for the different tests then they would be conclusive. In your case, my suggestion would be to repeat the test after 3 months. In the meantime, if you are concerned, you can consider testing with 4th generation HIV test.

  6. Hi Dr,

    I had a condom slip with a girl (did not notice any break).Dr put me on PEP around 60 hrs.I did a test at 3 & 19 from exposure and it was negative. I went to 1 of your clinic at 38 days from exposure and it was also Negative (rapid test) I noticed a rashes that come and go with Sore throat, swollen lymph around 20 days from exposure however Dr assured it is not an HIV rash and swollen lymph on left side of throat was not to be worry..however sore throat is still there (not severe) and swollen lymph (no pain)
    I am worried and wanted to know is this acute symptoms? I noticed white pus during urination through with no pain. Please help advise

  7. Lorenzolb

    Hi Dr.,
    After the intake of pep for 30 days , I had all symptoms of hiv including night sweats rash severe muscle , bone and joints pain but no fever I made a hit duo test and have test 24 weeks post exposure and it is negative both. I also did a PCR RNA test at 4 months post exposure and it was undetectable . My symptoms persist till now with mild red dots covering my body and front head and itchy scalp severe fatigue and neck pain.
    Is my tests 100 % conclusive ?? Or I need to test more than 6 months ??
    Did u ever heard someone seroconverted after 6 months with pep ??
    Please advice because I am loosing my mind and my symptoms is getting worse .
    Thank you.

    • Dr. Julian Ng

      Hi,

      It is unlikely your symptoms are due to HIV as you have been tested repeatedly negative. However, your symptoms may be due to other STDs or may be other medical conditions. Please visit a doctor for further evaluation.

  8. Hi dr, i would like to knw is the pcr rna test at 10days is good indication? What i concerned is i got taking pep for only 1 day. Will the pep effect the accurate of the test result?

    • Dr. Julian Ng

      Hi,

      WHO/CDC do not recommend using HIV PCR test as screening for HIV. My suggestion would be to test with 4th Generation HIV Combo test after 28 days post-exposure or after you have finish the course of PEP. Please visit a doctor for further evaluation.

  9. Allizzwell

    Hi Doctor

    I tested 28 days after PEP, making it 58 days. It was negative. Is this result conclusive or do I need to test further?

    I had cold, cough, splitting headache while lying down (just one night), throat irritation, runny nose, etc. on days 53-55 max. Then I have since been okay. Could these symptoms be ARS?

    I hadn’t had these for a while but as summer is beginning, I took fruit juices and yoghurt by the b night before I was struck with

  10. Please help

    I’m a male who had sex with a sex worker in the dominican republic 26 days ago. I went on pep (truvada and isentress) 68 hours after the exposure. Yesterday, I started to get a slight fever and had a sore throat. Today I went to the emergency room to get the rapid fourth generation hiv1, hiv2, and p24 antigen blood test. The results were negative. This is day 23 of Pep. I have 5 days left. Is this test conclusive?

    • Dr. Julian Ng

      Hi,

      You are still within the window period of the HIV test and thus the result is NOT conclusive. You will need to repeat it after 28 days.

  11. newyorker416

    Dear Doctors,

    Thank you so much for a wonderful informative website, it has helped keep my sanity in the past month. In early February I had a possible exposure (unprotected anal) with a man of unknown status. I started PEP less that 48 hours later. During my final week of PEP I started to get severe muscle aches, and joint pain. And a sore throat that is still here today. Severe headaches as well, Also lots of stomach issues. On March 12th I took my HIV test at the top hospital in NYC (also where pep was prescribed) and yesterday I got the negative result. It was the 4th gen AB/AG Lab blood draw test, not finger stick. I’m worried that this could possibly be a false negative because of my symptoms. My doctor said not to worry and that this is basically 100% conclusive. I started prep now but I’m still very anxious.
    I’m hoping my symptoms are just from the anxiety and not ARS. I spent the month in severe anxiety.

    Do you think I can breathe a sigh of relief and stop worrying? Is this test result based on the type of test accurate at 5 weeks post exposure even when taking pep? Thanks in advance for your answer.

    • Dr. Julian Ng

      Hi,

      I would agree that your result is conclusive. Your symptoms may or may not be HIV related. Please visit your doctor for further evaluation.

      • newyorker416

        But how could they be hiv related if my test was negative?

        • Dr. Julian Ng

          Hi,

          Assuming that the HIV test you did on 12th March was after 28 days post-exposure and it is negative, it is likely that your symptoms are not related to HIV. However, you should still seek further evaluation for your symptoms as there could be other medical conditions that can cause your symptoms.

  12. Doctor,
    I am on Prep (TenvirEM) for the last 60 days.

    I am planning to stop Prep.
    But recently 3 days back I had Unprotected sex with a Sex worker.

    So to stop PREP how long I should take Prep after Unprotected sex ?

    (On a very before day of Unprotected sex I missed I dose of Prep. But apart from that all 60 days I took Prep)

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