Why are swab tests much more accurate than blood tests?
In: Biology
I assume you mean to test for Coronavirus infection, because in general, blood tests tend to be reasonably accurate.
But blood tests can only test for what’s in your blood. Most viruses don’t infect your blood, and Coronavirus isn’t one of them. So we take samples from where it infects — the nose and back of the throat. Then we can test for the virus directly. These types of tests are generally quite easy to make and laboratories are already set up to do hundreds or thousands of them, they just need to know the Coronavirus specific ‘code’, and they can test for it.
Blood tests for coronavirus test for antibodies, which are molecules that we make to help clear the virus. Most tests for antibodies are very accurate, because antibodies are highly targeted seeker molecules, they can find *exactly* what they’re looking for. However, it takes a long time to develop a really good antibody test, so that’s why currently swabs are probably better. Eventually, it’s likely that a high quality blood test will be developed, but it won’t necessarily be able to detect an infection that’s just started, so in that case there’ll always be a role for swabs.
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