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How do Lions know Matthew Stafford had a false positive?

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NFL Chief Medical Officer Allen Sills joins Mike Florio to discuss how professional leagues are learning from each other, the role of testing, a "virtual football bubble" and more.

The Lions announced on Tuesday that quarterback Matthew Stafford had a false positive test for COVID-19. That claim leads to a fairly important question, one that may come up against and again this year: How do they know it was a false positive?

“As a result of a False-Positive test result, he was forced due to NFL/NFLPA protocols to sit out until he received two negative tests,” the team said in its statement. “His testing sequence for the Pre-Entry period was: negative, negative, False-Positive. The next three tests were all negative. To be clear, Matthew does NOT have COVID-19 and never has had COVID-19 and the test in question was a False-Positive. Also, all of Matthew’s family have been tested and everyone is negative.”

Again, how do the Lions know it was a false positive?

The Lions presumably are assuming it was a false positive because it was sandwiched around multiple negative results. In theory, however, the negatives could all have been false. (The chances of that many false negatives is slim.) Or perhaps Stafford could have had the virus for a very short period of time.

Regardless, without some sort of a clear, objective test that declares the positive result to be false (for example, a re-test of the exact same sample that tested positive), there’s no way to know for sure that it was a false positive test. So why insist with such clarity and certainty that it was a false positive?

That said, false positives happen. False negatives do, too. If false results are being generated, they can cut both ways. This leads to perhaps the biggest concern the NFL should have regarding COVID-19 testing: How many false negatives will happen, resulting in a player or coach slipping through the cracks and shedding virus and infecting others in a practice or a game?