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.
Hey my last test was done three and half months after my exposure is there any need to test again and can I get a positive test after a six-month period?
You have no need to be worried. If you have had 2 negative tests then it is almost impossible for both to be false negatives. You do not have HIV. You need to move on and forget about this incident.
Hey so a year ago I had unprotected sex, after I had tests done everything came back negative, then just a year after the unprotected sex I still wasn’t sure so I had another HIV test done(one year later) and that came back negative, but for some reason I still can’t trust it and I havnt had any sexual intercourse in anyway since the first incident over a year ago, and I can’t stop wondering what if I had a false negative on my last test done a year from the incident? And what are the chances of a false negative test done 12 months from the unprotected sex incident?
The difference is that the person who tested positive at 14 months had only had 1 previous test. A false negative is very rare. It is not possible for you to have had so many negative tests and still test positive for the same exposure. You do not have HIV. You do not need to test again. You need to move on and ensure you protect yourself in the future to avoid experiencing this level of anxiety again.
Sorry to bother you – am in serious difficulties re testing – I have tested at 5 weeks, 8 weeks, 10 and 14 weeks with insti p24/antibody tests then because of symptoms such as a white tongue, muscle ache, oral ulcers, jaundice dry mouth/eyes, recurring asthma, dry skin, I tested again at 4 months, 5 months, 6 months, 8 months, 9 months and 10 months at three different GUM and private clinics using ELISA and DUO tests. All tests were negative. I did full panels for all STIs and all came back clear – my doctors have done full bloods and only thing they found was an escalated WBC count which then tailored off and high billirubin (they checked it wasn’t hepatitis). After reading that one guy had 6 months neg and then 14 month positive test result (above) am petrified – am so symptomatic and was told 3 months was conclusive -or 6 months worst now I read about 14 months?
Thanks Simon and Charlie.I got the point.Will only come back to you after testing at 13th week.Thats just for my peace of mind and that will be sixth test on the trot!!!.
The message from Simon is loud and clear.It is we who choose to experiment despite having a knowledge of facts and factual!!!
Thanks to God who has showered blessings and made me stayed negative.
Thanks to you Simon and Charlie.God bless you all and your organization the dedicated and the unselfish work you and your organization is putting.
Merry Christmas and Happy new year to all.
With signing of I MUST SAY ITS REALLY DREADFUL TO WAIT FOR THE HIV RESULT,THE WAITING TIME IS HORRIBLE AND TERRIFYING.THAT’S THE TRUTH I HAVE SPOKEN!!!
Thanks and Regards,
VJ
This level of anxiety and worry from having a simple blood test for a virus is unfortunately still common but if you took a few minutes to consider other people lives then it might help you be more calm.
What if you are HIV-positive? Then you would find a way to deal with it, and treatment will extend your life for many years.
Think perhaps about the millions of people who are already HIV-positive and getting on with their lives.
Waiting for an HIV test result is not torture.
Torture is torture – think about torture and waiting for a test result is not it.
Take control of your own sexual life. If you have taken a risk that might expose you to HIV, then take an HIV test.
Then wait for the result. For most people this will be negative, but if it is positive then there is a lot you can do to stay healthy with modern drugs.
Then use the experience to inform your future risks and choices.
Dear Vijay,
I am very sorry but we are a small organisation with limited time and resources and so cannot continue to answer the same questions again and again. I have answered your question several times both as personal e-mails and as comments on questions. You do not have HIV. You do not need to test again. If you are still feeling anxious then maybe you should seek some professional counselling for your anxiety. I’m afraid we can no longer help you on this particular matter.
Kind regards
Charlie
Dear Charlie,
I could’t stop my anxiety of testing further and got tested once again at 58th Day post exposure for the 4th time by some p24 +Ag/Ab HIV1/2 ECLIA test wich said-NON REACTIVE.wich was at almost 9th week post exposure.In another Forum answered by Dr BOB( the body),as per him even if test are being done at 9th week,the test are though assuring and encouraging but repeat test at 3 months has to be taken.Please do let me know that if there any sanctity of 4th Generation tests then?Any ways people are relying today also at 3rd Generation Antibody tests alone.
Also what are the percentage of people today who experience late seroconversion?I have tested for 4 times already and after reading your answer in your forum,i was very assured until i read the Doc BOB’s response about testing at 3 months mark irrespective of whether taking 3rd Generation or 4th Generation test.Dear Charlie,i am very very afraid once again,please do help and clarify.Is my tension and anxiety worth testing at 58th Day Mark?Today is 68th day post exposure ie 10th running week.Should i restest once again??Or testing differs from from person to person exposures.Please Please help and reply.Waiting anxiously.
Regards,
Dear VJ,
As I said before, I cannot help you. You do not have HIV. I can only give out information regarding HIV. I am not a doctor. Please go and see your doctor about the problems you and your wife are experiencing.
Best wishes
Charlie