MIT research27 Apr 2020 16:12
Antigen testing could be a faster, cheaper way to diagnose covid-19
Current coronavirus testing is plagued by a lack of resources. An antigen test could be a useful alternative that bypasses supply-chain bottlenecks.
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Coronavirus testing in the US is nowhere near where it should be. A recent road map suggested we need to test upwards of 20 million people every day in order to safely reopen the economy (we’re currently running around 150,000 a day). To scale up, we need to move beyond conventional methods—and that might require an entirely different type of test.
The gold standard for covid-19 testing is the polymerase chain reaction (PCR) test. In a PCR test, genetic material collected in a nasal swab is copied millions or billions of times over so that markers for covid-19 infection can be identified (the virus’s RNA is too tiny to identify on its own, but making more copies makes it easier to find). PCR testing isn’t perfect, but it’s seen as the most accurate form of testing available for viruses. Unfortunately, it takes time, energy, and trained personnel to run these tests. That makes PCR testing too hard to scale up to the numbers we really need.
“There will never be the ability on a [PCR] test to do 300 million tests a day or to test everybody before they go to work or to school,” Deborah Birx, head of the White House Coronavirus Task Force, said on April 17. “But there might be with the antigen test.”
What’s an antigen test? While PCR tests look for evidence of viral genetic material, and antibody testing detects human antibodies against the virus, antigen tests look for fragments of viral surface proteins as a marker for infection. (An antigen is the part of a pathogen that elicits an immune response.) These proteins, usually from the coronavirus’s surface spikes, are big enough to study on their own, without spending time and energy making new copies.
Identifying their presence could mean a diagnosis of infection in just a matter of minutes, without expensive equipment, training, or power. In theory, a reliable antigen test could be pretty easy to scale up and could then be used in the home or at point-of-care locations. It could be the test we need to get America back on its feet again.