If blood samples from 2017 have similar number of positives as blood samples from 2019, then we can be quite certain that the positive tests (or test) from Dece

If blood samples from 2017 have similar number of positives as blood samples from 2019, then we can be quite certain that the positive tests (or test) from December 2019 were false positives. (Which I think is already the vastly most likely explanation.)