PatriciaABSantos on Nostr: The blood samples are used for serology tests, where you find antibodies against ...

The blood samples are used for serology tests, where you find antibodies against viruses. It is also very useful, but your imune system takes time to create those antibodies (up to 4 weeks). Using PCR to detect active viral infection (before you can detect antibodies) is faster, easier and cheaper. If you had a symptomatic person with covid and did serology tests, you would find antibodies in the bloodstream. However, since covid spreads before the symptoms start, if you waited 4+ weeks to diagnose an individual and isolate it from the comunity, it would be a waste of time since that person spent the whole excretion time walking around and spreading covid. So they used PCR instead.