A tale of two tests: Vermont town left puzzled by positive, then negative, COVID-19 results By Hanna Krueger Globe Staff,Updated July 22, 2020, 7:18 p.m.
iebig would ultimately be one of 65 people who tested positive last week after completing the rapid antigen test offered at a private medical clinic in the heart of Manchester, Vt., a town of fewer than 5,000. News of an outbreak set off alarms in a state that to-date had fared well in the pandemic, registering the second-fewest cases in the country. Many local restaurants and retailers quickly shut down. The Saturday farmers market was canceled. State officials with little information scrambled to answer questions from reporters and the public as to how and where the outbreak began. But in Vermont, positive antigen tests — a relatively new way of detecting an active COVID infection — require confirmation by another test: a polymerase chain reaction, or PCR, test, the gold-standard used by the government, hospitals, and professional sports teams. Of the 65 people who’d received those positive antigen tests, 48 would ultimately test negative via PCR. Liebig was one of them. ..
Unlike PCR tests, which detect the presence of genetic material, antigen tests detect specific proteins on the surface of a virus ...
PCR tests, by comparison, are quite accurate but can take days to return results, rendering them obsolete since a person could have become infected in the interim period.
“We don’t have any independent validation on these antigen tests,” said Dr. Gigi Gronvall, a biosecurity expert at the Johns Hopkins Center for Health Security. “ ...
Rhode Island and Massachusetts include positive antigen tests in their daily case total, while Vermont and New Hampshire require confirmation via PCR. New York, where Liebig lives, is treating her as a presumptive positive case for COVID and mandating quarantine, despite her negative PCR test. Liebig is relatively certain she’s negative since she has shown no symptoms herself and no one around her has reported symptoms. - https://www.bostonglobe.com/2020/07/22/nation/tale-two-tests-vermont-city-left-puzzled-by-positive-then-negative-covid-19-results/?s_campaign=breakingnews:newsletter
There’s debate about the accuracy of the PCR test also.
It’s found that our own T-cells can kill the virus with no help.
When that happens, remnants of the shattered virus cells exist in the body. PCR will multiply these remnants into a full virus cell, and yield a positive result when the virus has actually been already killed by the body’s own defenses.
That’s what asymptomatic cases really are. You test positive but are not sick. Your body had already killed the virus and you will not spread it.
PCR multiplies the DNA of the shattered virus cells to result in a positive result.
We need a better test.