They are using RT-PCR machines and therefore know which Cycle the sample crossed threshold. It could be reported.

Don't worry about whether they had full length RNA for testing. The RNA is transcribed to DNA first, takes a special enzyme as this is not a natural process. Then a DNA primer, a short length of DNA, ligates to the DNA under test. Anything excess to the length of the primer doesn't really matter in the process. Those particular bases, in order, are all that matters. We make positive reference DNA for the tests. The primers are all purchased from IDT (now owned by Danaher), you can see it in the BOM for the test protocols.

Karl is perfectly correct to state that poor lab technique can cross contaminate the samples. The PCR amplification is huge, size of the universe huge. Remember the PCR only confirms the presence of the RNA that matches the primer, not the full 30k length of the Covid. It is like doing a string search for 3 words vs. looking for 2 pages to match exactly.

The researchers will use BLAST to try to ensure there are few false matches to wild DNA.

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Vaccination required? Not if we leave.
Now in Florida, heart rate dropping, nicer people