Even PCR fails.
One of my friends had classic CV symptoms, including loss of taste and smell.
I told him he had it.
PCR test negative.
I said you have it.
2nd PCR a week later, he's still sick. NEGATIVE.
I said, well I still think you have it but not sure any more.
He gets better and after a month gets antibody test: Positive.
What do you believe, symptoms or test, and IF test, which one?
It is astonishing what foolish things one can temporarily believe if one thinks too long alone ... where it is often impossible to bring one's ideas to a conclusive test either formal or experimental. J.M. Keynes