PCR stands for polymerase chain reaction. PCR testing was developed by Kary Mullis, PhD to study DNA genetic material. This was the lab technique created by Kary Mullis for which he was awarded the Noble Prize in chemistry in 1993. Unfortunately, he passed away in Fall, 2019 at the age of 74.
PCR was, and still is, only meant to be a manufacturing technique; it was never intended to be used as a clinical, diagnostic tool to detect viruses.