Question
Why do I need to repeat a 28-day negative HIV test at three months?
16 September 2023. Related: All topics, HIV testing.
I don’t understand how if a 28 day Duo test when negative is conclusive, why does the information on i-Base say …
“As with antibody tests, a small percentage of people may have a delayed response to HIV so people using this test four weeks after any potential exposure are routinely recommended to confirm a negative result three months later.”
I was negative at 35 days and was moving on with my life until I read this,
please help.
Answer
Note: Since 2021, UK guidelines recommend that a negative result at six weeks using a 4th generation HIV Ag/Ab test does NOT need to be confirmed with a second test. Testing earlier than 6 weeks still needs a second test to confirm a negative result. The earlier answer is kept online to explain the complications of HIV teting. See https://i-base.info/qa/11844
……………
UK recommendations have changed several times on this question. In 2010 when this question was first posted, UK guidelines routinely recommended retesting so the i-Base information referenced this.
Since 2014, the guidelines change to only recommend retesting if this was linked to a high risk of HIV. (See statement below).
Updated guidelines also recommend not having to wait for 28 days before testing. Instead, it is better to test as soon as possible and then retest 4 weeks later. This change was important. It stops people worrying and might pick up early infections. Unfortunately, we still hear of clinics ask people to wait 4 weeks (or longer) before testing.
Even with tests that are incredibly accurate, health care workers have a duty to explain the best chance for a confirmed negative status. The reason for recommending the confirmatory test is two-fold:
- A small number of people have individual responses to HIV that may not be picked up by the test at 28 days. When the tests are approved, this is based on a panel of responses from an extensive store of timed blood samples. These show that some samples pick up a positive test result after only a week and some after more than a month, but that most are positive for the p-24 antigen at around 15 days. Some people may not produce enough p-24 antigen for the test to pick this up though, so together with the antibody response, the combined test are still more than 95% accurate at four weeks.
- The second reason relates to the possibility that someone who is not picked up, might put another person at risk of HIV. This duty of care should be explained when you take the test the test and are given the results. So although you have almost certainly not caught HIV, you should use condoms with sexual partners, until the confirmatory result.
I wish there was an accurate test at two weeks or one day, but there isn’t. The technology is more complicated than most people realise, and the concern for future transmission of HIV, however slight the possibility, is a professional health care concern.
Please don’t let this cause you stress, you are almost certainly HIV-negative, but this is the detailed reason.
BASHH/EAGA Statement on HIV window period
November 2014
HIV testing using the latest (fourth generation) tests is recommended in the BHIVA / BASHH / BIS UK guidelines for HIV testing (2008). These test for HIV antibodies and p24 antigen simultaneously. A fourth generation HIV test on a venous blood sample performed in a laboratory will detect the great majority of individuals who have been infected with HIV at 4 weeks after specific exposure.
Patients attending for HIV testing who identify a specific risk occurring less than 4 weeks previously should not be made to wait before HIV testing as doing so may miss an opportunity to diagnose HIV infection (and in particular acute HIV infection during which a person is highly infectious). They should be offered a fourth generation laboratory HIV test and be advised to repeat it when 4 weeks have elapsed from the time of the last exposure.
A negative result on a fourth generation test performed at 4 weeks post-exposure is highly likely to exclude HIV infection. A further test at 8 weeks post-exposure need only be considered following an event assessed as carrying a high risk of infection.
Patients at ongoing risk of HIV infection should be advised to retest at regular intervals.
Patients should be advised to have tests for other sexually transmitted infections in line with advice on window periods for those infections (see BASHH guidelines at: www.bashh.org ).
Note: This answer was updated in January 2018 from an original post from October 2010. The additional note was added in September 2023.
Just wanted to say THANK YOU for this forum as a 27 yr old Gay man I have educated myself on HIV thanks to this page.. It’s most appreciate. As now learning 18 months of 3 HIV negative tests that I can breath a sigh of relief as 18 months ago I had stupidily had unprotected sex and lived the fear of getting HIV. But this forum page as put me at ease and the IMPORTANCE of safe sex. Thank u sincerly x
Having received 4 negative test results, one after the final window period of 3 months, you can be confident that you do not have HIV.
I’m sorry but i-Base no longer answers individual questions about risks of HIV transmission or HIV testing.
This service is based on information relating to treatment of people who are HIV positive.
Most testing questions are already answered on the FAQ page:
https://i-base.info/qa/faq/hiv-transmission-and-testing
Our guide to HIV Testing and risks of sexual transmission guide has more detailed and easy to read information about these topics. It can be read online at this link:
http://i-base.info/guides/testing
Sir while doing sex with a sex worker whose HIV status is unknown to me my condom broke. I just removed my penis and wore another condom until to reach my satisfaction. After 15 days I go for a Elisa test which comes doubtful. It really scared me I again go for another ELSA test after 20 days which comes negative but due to my fear I again go for another test after 1 and half month which also comes negative but because I’m in a great fear after this test I went to join some hard training of defense of 1 month with in this period i suffered fever and stomach pain also my urine comes out yellow i feel so stressful and when I come back from training i just consult doctor he found some stomach infection and also I go for another HIV test(tridot test) exactly after 3 and half month of exposure which again comes out negative kindly help me please I’m in a huge stress my eyes got rashed due to continuous reading of HIV window period on internet this was my last mistake please help me can i feel happy after this 3 and half month tridot result please reply
You need to be careful what you read on the internet as there is a lot of incorrect information out there. The virus is indeed very small but it still cannot pass through the condom. This is a common myth and there is no truth in it. For more information on HIV testing please follow this link
These results suggest you don’t have HIV. You can marry regardless of your HIV status.
i saw an article where written that hiv virus is so small that it can enter through out the condom…..after that i search on internet to know about it & report says that condom cant properly protect hiv it can only reduces the chance hiv………….also let me know what is HIV-1.HIV-2 test????is it antibody test???/& also let me know how accurate is the test of HIV1, HIV2 test????
hi sir, i had sex with a prostitute on 26 jun 2010 (first unprotected oral sex, then protected vaginal sex) i tested both screening, and HIv duo & p24 antigen test after 3 months of exposure both was NEGATIVE, again i tested HIV DUO & p24 antigen on 6 th jan 2011 i.e after 6 months which came NEGATIVE .
(Hiv anyibodies –
observation; patient value-0.00
cut off value-0.25
p24 antigen: patient value-0.01
cut off value-0.25)
sir please reply me .. can i get marry now ?, bcoz i dont want infect others,,,
and , no need to test again?
please , please i am waiting for reply and please make me panic free……
thank you
If you used a condom then you are not at risk of HIV. If your test was negative then you do not have HIV.
i had done my HIV 1, HIV 2 test after four and a half moths(140days) later of my last exposure which i made with condom…still i m frightened………..i did only one test & the result was non-reactive …….should i take again a test on 6 months????? plz response
Yes!!!Thats true and Charlie you havent spotted it and you have answered to his queries.First DDIN claimed that his 14 months test became positive and then he/she asking about test taken at three and a half months??Whats that.Where as you denied to comment to my post!!!