Talking about home testing for HIV

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Confused

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Window periods

Hi, I had one off unprotected vaginal sex, which I am aware is not particularly high risk, however over the last 7 weeks I have experienced flu symptoms more extreme than any previous occasion, this made me anxious so I decided to order the Biosure
test. I took the test at 5 weeks (35 days approx.) and the result was negative. Many people who have experienced this anxiety will be aware, that there is varying theories on window periods especially in the case of rapid tests. However, many health services claim 95% of people will have antibodies by 28 days, so my question is, is the Biosure test 95% accurate at 28 days? And if not why? Also if my symptoms had been occurring for a couple of weeks and my test is negative does that mean my symptoms are not HIV related? Thanks for your time.

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Gary Carpenter, BioSure (UK) Limited
 Work on 26th February 2018

Hi Confused Thanks for getting in touch. I will try to help. All effective rapid tests for HIV work through the detection of antibodies. These types of test are generally very sensitive and specific. They are very good at finding HIV when present and very good at determining when HIV is not present. However, this process relies on the person producing antibodies. The timing of this process is very variable. A very few people will make the required antibodies at around 3 weeks after infection. A very small number of people will not make antibodies until 12 weeks after infection. So a negative test result until 3 months, whilst very encouraging cannot be conclusive for any individual. The biggest risk associated with an HIV test is a False Negative, i.e. a negative test result when someone is actually infected. Testing too early increases this risk. So when we make claims about probability of accuracy at different intervals after infection, we err on the side of caution and we have used consensus scientific evidence. This took the form of looking through all of the published data around the probability of a correct negative test result. This data indicates that at 4 weeks after infection around 80% of people would have created antibodies. So most but by no means all. The flu-like symptoms associated with HIV infection are a function of antibody creation. So with regard to your symptoms if you had been experiencing them for two weeks prior to a negative test it is extremely likely that an HIV test would have been positive. I hope that this answers your question and helps to remove some of the confusion. Kind regards Gary Carpenter BioSure (UK) Limited

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