Talking about home testing for HIV

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Unsure Millie

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Control line concern

I carried out the test recently and I am just curious about how the actual control line works. I would like to know what triggers the control line on the test?
For example, would the control line be triggered if only the buffer solution was put in the test and no blood?
Or is it only triggered when the correct sample of blood is applied to the test?
The reason I am asking this question is because I feel in my test, much more buffer solution was applied than blood. At first my test did not run because I hadn’t the device pushed fully into the buffer pot but when I realised it wasn’t pushed in after the first 15 minutes, I immediately pushed it in and I gave the test device a few firm shakes and the control line appeared fairly quickly at that point. Quite a lot of solution spilled around the device and I’m just worried that it would have invalidated the test result? My result after 15 minutes was a solid red control line only but I noticed that the corners of the test line has a very faint dot of very pale pink but this seemed to disppear after a few minutes. Can I trust that my test was valid and I’m negative? I’m just very curious about what actually makes the control line appear and would it appear if only buffer solution was put on it. Your help would be greatly appreciated.

3 Responses

Gary Carpenter, BioSure (UK) Limited
 Work on 14th August 2017

Hi Unsure Millie The fact that you now have two negative results from two completely different sources means that you can be completely confident in your negative HIV status. To answer the question about the slight discolouration on the strip around the test line area while the test is running. The lines on the test work a bit like a sophisticated fishing net. Once the test has run the fishing nets will only have captured specific things. In the case of the test line, HIV antibodies. However, while the test is running some things can be temporarily "snagged" by the test line. But they don't stick. As more buffer washes up the test these non-specific things get washed off. This is the main reason that we say that the test should not be read too soon after starting it. I hope that this makes sense and answers you question. Kind regards Gary

Unsure Millie
 Used on 13th August 2017

Thankyou for your informative response and settling some of my concerns. I feel more confident now that I can trust my test result when you have told me that the control line will only trigger if the correct amount of sample is used. I just have one little thing that still troubles me. The control line appeared very quickly and was solid. However, I was concerned as I thought I noticed the corners of the test line look as though it was turning a very pale pink. Maybe just on one side even. However, no line appeared and the very faint corner colouring disappeared too. Have you any explanation as to why the corner of the test line would appear to show an extremely faint pink dot but no line appear? Should I be worried about my negative test result? As far as I could see, there was only one clear completely visible line and that was the control line. I'm very anxious about my test result and would like to trust that it is valid and true. I have taken a DrThom HIV saliva test recently also which came back with a negative result from the lab. I'm just afraid to feel confident in my result incase I'm wrong

Gary Carpenter, BioSure (UK) Limited
 Work on 09th August 2017

Hello Unsure Millie Thanks for getting in touch. The control line is a sample control line. This means that the test will only produce a valid result (i.e. trigger the control line) if human blood and the buffer has been applied. Applying buffer alone will NOT produce a valid result. The test requires only 2.5 microliters of blood but will absorb around 120 microliters of buffer. The buffer pot contains about 3 times the amount of buffer needed. The test is designed to be robust against slight errors in performing the steps required to conduct the test. We feel that the inclusion of a sample control line is a really important requirement for a self-testing device. It provides a mechanism for the users to quality control their own test. Since you produced a control line you know that the test has been conducted successfully, and you can be confident in your result. I hope that this answers your questions. Kind regards Gary Carpenter BioSure (UK) Limited

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