Talking about home testing for HIV

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Not Sure if Blood Sample was enough

I did the biosure test exactly 3 months after a possible exposure and then again 2 months after that (so 5 months after possible encounter) and the result came back negative both times. I’m not sure I performed it correctly because during the first test I didn’t realise the tube to collect blood worked by capillary action so I kind of scooped the blood in, I didn’t know if it was enough so I kept on pressing the tube on the blood spot to take more in (I don’t know if this let out the blood or not and I’m not sure if the inside of the collection space was just simply stained with blood or if the sample was actually still in there in the right amount). I ran the test and it showed the control line, 15 minutes later it was negative (only the control line was showing).

The second time I messed up the lancet and had to cut my finger with a knife to get the blood (not sure if the sample was enough this time as well). I did the test and it came back negative again.

I would like to know how the control line works, i assume it appears when the buffer solution reacts with a protein in human blood, if that’s the case then wouldn’t any amount of blood be able to make it show? (For instance if the walls of the collection space are stained with blood but there is not actually enough of the sample inside for a valid result) and if that’s true wouldn’t that give a false negative since there probably will not be any antibodies in the tiny amount of blood that has been tested?

1 Responses

Becky, BioSure UK Ltd
 Work on 30th July 2020

Hi MysteryMeaterson, The BioSURE HIV self test has a built in sample control line which will not appear if the test procedure is not followed correctly or if the test strip is faulty. In both circumstances, as long as the control lines were visible, you supplied enough blood and your test results are accurate. The test is lateral flow and therefore runs from the bottom up. The test itself requires a very small amount of blood to run (2.5ul) and once the tip of the test touches the blood sample it sucks it up by capillary action. When the blood mixes with the buffer solution, it will begin to run up the strip. If there are antibodies present in the blood, the test line will be visible. The test line is sprayed with synthetic peptides that represent HIV antigens. Binding occurs only if the test detects antibodies in your blood. If the test line is absent and only the control line is visible, your test result is negative. False negatives occur when user test inside the window period and therefore even though someone may be infected, their body has not produced enough antibodies for the test to detect infection and therefore cannot bind to the test line and the line will not be visible. Since you have tested both times outside of the window period, and the control line was the only line visible at the time, then your results are negative. I hope this helps. If you have any other questions, please feel free to leave them below. Kindest regards, Becky

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