I think you have that backwards. False negative seems extremely plausible. If you're sick, but your viral load is low, it should be possible to collect a sampl

I think you have that backwards. False negative seems extremely plausible. If you're sick, but your viral load is low, it should be possible to collect a sample without a virus particle. If the sample doesn't contain a viral particle, it will necessarily come back negative. False positive seems unlikely, as you'd have to have something that survives several cloning cycles that ends up looking exactly like the markers you're matching against.