The problem is that that false positives from that method will be replicable within the same sample source. If there is a stretch of DNA sequence that matches closely (~90%) to the primer sequence used to bind the dna for amplification and detection (these are generally 15-40 base pairs), then it’s possible to get a signal from something not related to covid. This could be another closely related coronavirus, or really anything - it could even be a mutation in some persons genome that gives the primers something close enough to bind to.
The covid primer pair is good, but it’s not perfect. That’s why caution should be used when testing like this.
My assumption is they’re testing by PCR?
The problem is that that false positives from that method will be replicable within the same sample source. If there is a stretch of DNA sequence that matches closely (~90%) to the primer sequence used to bind the dna for amplification and detection (these are generally 15-40 base pairs), then it’s possible to get a signal from something not related to covid. This could be another closely related coronavirus, or really anything - it could even be a mutation in some persons genome that gives the primers something close enough to bind to.
The covid primer pair is good, but it’s not perfect. That’s why caution should be used when testing like this.