Presumed positive for COVID-19 vs. confirmed positive
MONTPELIER, Vt. (WCAX) - While the Vermont Health Department is tracking an apparent outbreak of COVID-19 cases in southern Vermont, some of them won’t appear on the state’s COVID-19 statistics yet.
That's because the health department says the tests aren't accurate enough to be confirmed positive, just presumed so.
The health department says the tests used by the Manchester Medical Center are antigen tests.
Both traditional PCR tests and antigen tests are done with a swab in your nose. But antigen tests only look for a specific protein on the surface of the virus. They’re attractive because the results come back in minutes, unlike PCR tests.
Vt. Health Commissioner Dr. Mark Levine says that makes them a good screening tool. He also said if you get a positive result on an antigen test, it's likely correct. But he also said antigen tests aren't as sensitive and have a higher false negative rate, meaning you could have the virus and have the test not pick it up.
But Levine says presumptive cases are still taken seriously.
"Just because we call them a presumptive positive doesn't mean we don't go through all of our usual counseling and advising and isolate out those who have tested positive, begin to contact trace and notify those who are contacts," Levine said.
On its Facebook page Tuesday, the Manchester Medical Center said over the past 72 hours, they have had 42 positive cases and likely 30 or more false negative tests.
The center says the antigen tests have a 12% likelihood of being inaccurate. They go on to say that's only 6% less accurate than a PCR test.
But they say what’s crucial to stopping the spread of the virus is the speed of the results. So people who likely have the virus know quickly and can take precautions faster.
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