After an earlier rapid coronavirus test returned a positive result for Ohio Gov. Mike DeWine, a second coronavirus test for DeWine, came back negative.
“The test administered this morning to the Governor in Cleveland, as part of the protocol required to meet the President, was an antigen test”
Question 1: How accurate is an Antigen test?
From the Mayo Clinic: "A positive antigen test result is considered very accurate, but there's an increased chance of false negative results - Read
Unlike PCR tests, which detect viral genetic material, antigen testing is designed to determine if a sample contains proteins found on the surface of the coronavirus, enabling the delivery of results in minutes rather than days.
The trade-off is that while the slower-to-process PCR tests are typically highly accurate and usually do not need to be repeated, negative results from antigen tests may need to be confirmed with a molecular test, according to the FDA. In particular, antigen tests are not able to definitively rule out active COVID-19 infection, the agency has stated.
Testing Update: "Quidel says its COVID-19 antigen test is now on par with PCR accuracy" - Quidel Corporation shared new data showing its COVID-19 antigen test has 96.7% sensitivity within five days of the onset of patient symptoms.
What about false positives? (and the anxiety that goes along with them)
Are these counted in the "total" coronavirus case count, even though they were incorrect?
"The flaw, which has been reported to both the manufacturer and the federal Food and Drug Administration, led to 90 of 144 people tested during June 15–July 17, 2020 receiving a false positive COVID test report"
But, what do they consider "very accurate"?
As a result, most antigen tests have a sensitivity of anywhere between 50% and 90%—in other words, one in two infected people might incorrectly be told they don’t have the virus. Last month, Spanish health authorities returned thousands of SARS-CoV-2 antigen tests to the Chinese firm Shengzhen Bioeasy Biotechnology after finding the tests correctly identified infected people only 30% of the time, according to a report by the Spanish newspaper El Pais.
How many people are receiving a "false-positive"?
The sensitivity of antibody tests is too low in the first week since symptom onset to have a primary role for the diagnosis of COVID-19. Sensitivity has mainly been evaluated in hospitalized patients, so it is unclear whether the tests are able to detect lower antibody levels likely seen with milder and asymptomatic COVID-19 disease.
"Governors of Maryland, Louisiana, Massachusetts, Michigan, Ohio, and Virginia Announce Major Bipartisan Interstate Compact For Three Million Rapid Antigen Tests"
There are obviously some serious issues with testing
- Some antigen tests used in the past miss up to half the infections they look for
- Texas Department of State Health Services removed more than 3,000 COVID-19 cases from its statewide coronavirus database because San Antonio was reporting probable cases for people who had never been tested for the disease.
Testing needs to be improved. It is hard to trust anything we see (or hear) in all of this chaos. The science just is not there yet. Until we have an effective vaccine, my advice is: mask up, eat healthy, exercise, and turn off the news. The stress just isn't worth it.