How the SARS-CoV-2 Antigen Tests Work

As of August 27, 2020, the U.S. Food and Drug Administration (FDA) has issued 3 Emergency Use Authorizations (EUAs) for COVID-19 tests to detect the presence of SARS-CoV-2 antigens in patient samples.The two main assays currently used in the United States for SARS-CoV-2 include molecular (PCR) assays (to detect viral RNA during active infection) and antibody assays (to detect host antibodies developed against previous infections).Antigen testing, which detects the presence of viral proteins rather than viral RNA or host antibodies, offers a third option.

The Role of Antigen Testing in COVID-19

Using diagnostic assays to detect COVID-19 in the United States has been challenging for a variety of reasons, including supply chain shortages, funding and staffing challenges, and an overburdened healthcare system.It is important to understand that different SARS-CoV-2 testing methods have unique uses in this pandemic, and there is no one-size-fits-all crisis solution.While PCR tests are very sensitive and well suited for diagnosing acute infections, they are expensive and require the use of special reagents, equipment and specially trained clinical laboratory scientists, all of which have so far been stretched during the pandemic. Serological tests can be used to determine whether someone has been infected with SARS-CoV-2, However, since antibody production takes 1-2 weeks, it is not recommended for acute disease diagnosis.Antigen tests are less expensive to produce than PCR tests and can be performed very quickly, making them a worthwhile option for OL screening.Once more Relial AntiGen tests hit the market,potentially millions of antigen tests are performed each day in the U.S., which will help reduce the testing burden in some places. While molecular testing is possible in real time, supply chain and throughput challenges have made this impractical during the COVID-19 pandemic.Implementing antigen testing in COVID-19 testing algorithms could reduce pressure on laboratories and preserve molecular testing for conditions requiring high test sensitivity.The advantages and disadvantages of SARS-CoV-2 antigen testing need to be considered to determine if and when it is a reliable method for COVID-19 diagnosis.

Advantages

Antigen testing is cheap and fast. Knowing that molecular testing cannot continue to carry the burden of all acute COVID-19 testing in the United States, antigen testing offers a solution to the need for tests that can be produced cheaply and run quickly.Antigen testing may be a useful public health tool. Because antigen tests are generally considered very accurate when positive, they may be useful in quickly identifying highly infectious individuals within the community.However, it is important to note that antigen test performance may be poor in areas of low disease prevalence, and data on test performance in asymptomatic individuals are limited. Because antigen tests are more likely to be positive when a person has a higher viral load, superspreader events or outbreaks can be prevented by identifying these people early and putting them into isolation.Potential for use in point-of-care settings.The rapid nature of antigen testing and less reliance on expensive equipment and reagents make it ideal for point-of-care testing.This reduces the testing burden on laboratories and provides rapid results where patients are tested.It's important to note that point-of-care sites must have a CLIA certificate to run these tests, so locations where they can be offered will vary.