Is antigen testing really a “game-changer”?
Updated: May 12, 2020
In the last 48 hours, the FDA issued emergency approval to Quidel Corp’s antigen test for coronavirus. This antigen test is a diagnostic test for Covid-19 that will be more rapid and cheaper than the existing tests for Covid-19.
The test is called the Sofia 2 SARS Antigen FIA and can be used as a point-of-care product with the existing Sofia 2 machine. This feature will allow a rapid rollout since these machines are already seen in doctors’ offices and other health care facilities.
Immediately, the emergency approval was hailed as a “game-changer” by Dr. Scott Gottlieb and a “breakthrough innovation” by Dr. Deborah Birx.
Similar to the existing test, the new Quidel antigen test also uses a swab applied to the nasopharyngeal cavity. This test can detect fragments of proteins found on or within the virus. This technique differs from the existing test which detects the DNA or RNA of the virus and amplifies it by laboratory detection by a polymerase chain reaction (PCR).
In actuality, the antigen test poses both some theoretical advantages and disadvantages from the existing Covid-19 test. Since many of the machines are already in use, the test will be widely available on a relatively quick basis. The antigen test does have quicker turnaround over the standard test. As a point-of-care product, it also uses less expensive materials and is cheaper to run.
However, the product has some disadvantages. Most importantly, it is also thought to be less sensitive than the current test which is able to amplify the genetic fragments it is examining and create more sensitivity. Rapid antigen tests are similar to the tests used to detect strep throat and flu. Those tests are notable having fair sensitivity or ability to detect the disease if it is present but high specificity meaning being highly correct when giving a positive result.
So why is it being hailed as a “breakthrough.” Due to its quick turnaround and hopefully ubiquitous locations, the test could become an excellent first-pass screening for the virus in symptomatic patients. For those with high suspicion of disease, it will be however valuable to perform a subsequent test with the standard test to exclude the disease. The value of this strategy will be in its expediency and ability to perform immediate contact tracing of the individual’s contact.
There are some other scenarios where it could be used. Employers could use this test as a screening test for putting their employees back to work. No one knows whether this approach will prove valuable as the rate of asymptomatic individuals harboring the disease will be very low. Additionally, this antigen test is thought to lack even more sensitivity on the early phase of the disease onset.
We do think this is something to watch closely, and possibly be another tool in your COVID-19 Battleplan. For more information, read this article.