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
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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.
Im wondering why DDIN is telling different stories really!Firstly he tested negative at six months and positive at 14 months,next two stories are different from the first comment,whats going on?
This is answered in the reply to the question you have commented on. Please re-read the answer above as this gives a very full response explaining about the tests and when they are accurate.
Dear Charlie,
I m in deep trouble really,i had been involved in unprotected sex with a sex worker 2 times the last one was in Mid October.Since then i have taken 3 ECLIA test as i was told that these are reliable test.Oral sex was also involved i was receptor as well as i gave her as well.The sex lasts for about 15 minutes.The last test i took at 83rd day my last exposure besides taken at 5th week and 9th week.
I want to know are tests conclusive.I feel some dizzy at times apart from persistant neck pain. Are these symptoms related to ARS?.Is dizziness could be a symptom of ARS?
rgds,
Akumar
I have answered this question several times already as e-mails and comments under different names. Due to limited resources we cannot continue to answer the same questions again and again. You cannot get HIV from receiving a blowjob. You are not at risk and so do not need to test again.
Can you please tell me for whom testing is necessary after six months? Is that needed for me also or should I move on? I don’t have any symptoms of HIV and my HIV-1 and HIV-2 test was negative after three and half months so this test is conclusive for me because I had received an unprotected blowjob with a sex worker before 5 and half months.
Thanks in advance for your time
In some people it take 2-3 MONTHS not years for antibodies to show in the blood. This is because the test relies on the bodies immune response to a HIV infection which in some people can take a little while. This time is called the window period. For more information please follow this link.
Why do they said that it can take 2-3 years for HIV to show in the blood? Is this correct? What is the maximum time for HIV to show in the blood?
If you have had 5 negative HIV tests then your symptoms are not HIV-related. You do not have HIV. You should talk to your doctor about what is causing the thrush because it isn’t HIV.
Hi,
I had un protected sex with sex worker on July 31st. Exposure was for 5 seconds. I had the following tests:
14 days – HIV DUO test negative
28 days – HIV DUO negative
40 days – HIV DUO negative
62 days – HIV DUO negative
5 months – Finger prick test negative
I am having constant thrush from 12 days post exposure. Am worried, is it related to HIV? It’s not respoding to medications.
Please help me.
The test at 3 and a half months is conclusive. You do not need to test again.