Why are swab tests much more accurate than blood tests?
In: Biology
Cold viruses like coronaviruses does not target blood cells. So you can have a full blown infection in your airways and yet not any blood infection. This is why the most accurate test of coronavirus is swabbing the throat and nose where the actual virus is and not the blood where the virus is not. The blood tests that have been developed work differently in that they do not look for the virus directly but rather looks for antibodies that your immune system have made in response to the virus infection. These will be mainly present in the blood. However the antibodies only show up after you have had the virus for some time and your immune system have targeted it. On the other hand the blood test will show a positive result even long after the immune system have beaten the infection. We do not yet know for exactly how long as we have only been testing people for three months. So a negative blood test for coronavirus may mean that you have only gotten the infection recently and a positive blood test may mean you have had coronavirus but no longer. Both tests are of course usefull but in different ways.
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