>They control the number of false positives by canging the cycles of amplification. At 30 cycles or less >80% of the swabs that test positive can be cultured for sars cov 2 But PCR is not a test. It can't be used to prove an infection. You try to defend it, but Kary Mullins, who created the test, and understood it talked about it clearly that it is not something that can be used for that purpose.