You really are in over your head. Stop before you make a complete ass out of yourself.
PCR is a confirmatory test. It in fact shows the presence of the target of study. You need to learn to do arithmetic before calculus. Trying to explain the complexities of medical testing to someone who apparently has no clear understanding behind cut and paste is impossible.
Then provide an article that shows isolation and how it was performed, and I will study it. And stop being a dismissive a$$.I am not in this for anything other than definitive answers.