Thanks Gary one of the worst things connected to the fear of having hiv is the constant search for reasons why a negative result could be 'false negative'. I have now had 4 Biosure self tests and a labo test through my GP in Belgium (for and exposure which was more than a year and a half ago) and I am still look for reasons they could alle be false negatives (because of symptoms which I have been told could be caused bij stress). This is also despite the advice of a medical worker at our regional Aids Referral centre telling me that the Biosure test is even more sensitive than the regular screening test used in Belgium. This fear factor underlines the importance of the Biosure 'package' which includes the forum and you own incredible accessabilty. In Belgium we have a similar test (Autotest), but without the 'wrap around' package you provide, and believe me without this package the stand alone test product is incomplete. Thanks again

Hi Sam Thanks for contacting us again. There is no evidence that increased levels of magnesium will interfere with the performance or the result of the test. I hope that this puts your mind at ease. Kind regards Gary

can magnesium tablets taken in the morning cause a false negative Biosure hiv test carried out in the afternoon on the same day the tablets were taken? I tested negative but am worried because of the magnesium tablets.

Hi Sam, Gary is travelling at the moment and as Clinical Director is best placed to respond to your questions, but I just wanted to jump in quickly about the issue of false negatives, as it is the biggest risk associated with self testing for HIV. It is not solely about device performance in a laboratory and data interpretation. There are a number of unregulated tests (some claiming to be regulated) available in various markets that will produce a control line even if NO BLOOD is applied, only the buffer solution. These products often require a large amount of blood that needs to be measured by the person doing the test. Given that many people are really anxious when they are testing, they could easily collect and use an insufficient volume of blood but will still have a control line appear. This is incredibly dangerous as the tester will read this as a negative result which may in fact be false. Should they be positive they would not know to seek treatment and could unknowingly onwardly transmit the virus. The BioSURE HIV Self Test will ONLY produce a control line (negative result) if the test has been performed correctly AND sufficient blood has been used. I'd also like to highlight that our test only requires 2.5 microlitres of blood (a fraction of a drop) and that the testing device collects the blood automatically so there is very little room for user error. If there is a mistake no lines will appear. Just Prick, Suck, Poke as we say. I hope that helps provide a little insight

just to clarify my second question, false negatives within the 3 month window would not be considerd a failure of the kit, a false negative outside of the window however could be considered a failure of the kit. How dit the researchers calculate the 3 in 1000 odds?

when you use the figures 3 in 1000 does possible false negatives does this refer to false negatives outside of the 3 month window or a total of 3 for every 1000 tests regardless of they were within or outside of the 3 month window?

Hi Sam Thanks for getting in touch, you have asked a really good question. There a couple of things to point out. Firstly, it is really difficult to know when a false negative has occurred. By their very nature they go pretty much unknown. This is the case for all types of tests. No test, regardless of what people might publish, will always be 100% accurate, 100% of the time. To put this into numbers we think that around 1% of people who use the BioSURE HIV Self Test will be infected with HIV. The vast amount of evidence collected by us and independent researchers indicate that around 3 in every 1,000 positive cases will not be detected by the test. So that equates to around one false negative in every 33,333 tests sold. So we've probably had more than one. Secondly, the most likely cause for a false negative will be someone testing sooner than advised. This is particularly exacerbated by the nature of the test and the individual's reaction to an HIV infection. The BioSURE HIV Self Test works by detecting antibodies, so it cannot work until a person has produced these. This process is not set in stone and is actually quite variable within the first 3 months after exposure. Around 95% of people will have produced the antibodies necessary around 6 weeks after exposure. But some will not until 3 months after exposure. So we make it absolutely clear that the BioSURE HIV self test may not provide an accurate negative result until 3 months after exposure. I hope that this helps to answer your question. Please don't hesitate to contact me (gcarpenter@biosure.co.uk). Kind regards Gary Carpenter BioSure (UK) Limited