Talking about home testing for HIV

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Test sensitivity

if I have understood well every 1000 positive samples your test could give 3 false negatives (theoretically speaking).
My question is, what are the reasons for these false negatives? Does it depends on specific person? I mean, if a person has a false negative he will continue to have false negatives?
Thank you.

7 Responses

Francesca Bard, BioSure (UK) Ltd
 Work on 17th July 2019

Hi JLP, thanks for your question. No, you should not worry about sticky antibodies, this was just an easy way to explain the mechanism of how the HIV antibodies in various positive samples can vary and is not something to worry about. The fact that you have had two negative test results outside of the window period mean you can be confident in your result. Kindest regards Francesca Bard, BioSure (UK) Ltd

 Used on 15th July 2019

I have never heard of sticky antibodies. I have had 2 negative Biosure tests, should I be worried about sticky antibodies now? Both the negative tests were well outside the window period and for the same exposure. The mention of sticky antibodies has made me question their accuracy. Just to clarify that I have understood correctly. The possibility of 'sticky' antibodies are just one possible reason for a false negative, since false negatives are rare can I still be confident that the 2 negative Biosure results I have received (taken well outside the window period) are correct?

Gary Carpenter, BioSure (UK) Limited
 Work on 01st August 2018

Hi BigQ I hope that I can help to clarify. There are a number of reasons why someone might get a false negative test result. The BioSURE HIV Self Test detects a person's antibodies rather than the virus itself. One of the most likely causes of a false negative is that the person has produced a low level of antibodies when tested. This itself can be caused by a number of things: taking PEP or PrEP can delay antibody creation or the person maybe in the early stages of antibody creation, for example. Another possible cause is the "stickiness" of a person's antibodies. Whilst all antibodies are similar the antibodies produced slightly different between people. Rapid tests are generally just not as accurate as large, laboratory instruments. Unfortunately few diagnostics are perfect. The BioSURE HIV Self Test has been developed and tested to ensure that it is very accurate. I hope that this helps to answer your question. Kind regards Gary Carpenter BioSure (UK) Limited

 Used on 24th July 2018

Dear Francesca, thank you for your answer but probably I was not clear in my question. The BIOSURE test gave 99,7% sensitivity after official product testing - meaning that it lost (giving false negative) some people certainly and officially HIV positive, not people in window period or on PrEP. Why this happens? Thank you.

Francesca Bard (BioSure UK) LTD
 Work on 20th July 2018

Hi Bigquestion, I am sorry for the delay in getting back to you. The most likely explanation for a false negative is generally due to the window period and seroconversion, when a person is actually making the antibodies to HIV and the level of them in their blood may be very low. It is also possible that someone on PrEP may have the same outcome if they had a viral infection, because their antibody production could be supressed due to the medication. HAMM is right (thank you for posting back!) that if a person gets a false negative outside of the couple of reasons stated above, they are no more likely to get another false negative. I hope this helps. Kindest Regards, Francesca Bradford, BioSure (UK) LTD

 Work on 16th July 2018

I am not scientist or great medic expert - but I am very sure that false negative is not specific to a person. It happens a very small number of times and happens for random chance. If still worried - do second test. Random chance of 2 false negative is really not probable.

 Used on 11th July 2018

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