This column on COVID-19 testing was written by Michael Rosanoff, MPH, a member of the Bayonne COVID-19 Task Force and epidemiologist from Columbia University. To read the complete version, visit his blog at www.covid-19journal.com
There are different types of COVID-19 tests, each providing different information. Antigen testing tells us whether or not someone currently has a COVID-19 infection. Until recently, only individuals with symptoms could receive this test. This means asymptomatic cases were missed and more likely to spread the virus. The problem with widespread asymptomatic testing is that it doesn’t tell the whole story. An antigen test tells us one thing – do you currently have COVID-19? If the answer is yes, then you and any close contacts can self-isolate, preventing further spread.
What if the test is negative? You may not have the virus at the moment, but could still contract the virus at any point later on, even that same day. It could also be a false negative, meaning that you actually have the virus but it may be too early in the infection to accurately detect it. A negative test can, thus, instill a false sense of security. Widespread testing can also put a major burden on the healthcare system.
Each test requires personnel, testing kits, and personal protective equipment. Crowded testing centers may inadvertently put people at risk of spreading the virus. Asymptomatic testing may make sense in certain situations. Healthcare workers and first responders should be tested regularly, even without symptoms. Anyone who has been in contact with a known or suspected case should also be tested. Seniors and individuals with underlying health conditions could benefit from regular testing. And as we reopen aspects of society, certain types of employees like teachers, food service, and retail employees in constant contact with people, should have access to testing. Since a single test is only a snapshot in time, they would need to be tested regularly. The other type of testing is serologic – aka antibody – testing. The presence of COVID-19 antibodies signals that you already had the virus. Typically, if your body has antibodies to something, you have immunity. With the novel coronavirus, we don’t yet know for sure if the presence of antibodies alone means protection from re-infection or how long protection lasts. Because of this, antibody test results don’t tell us much, though hopefully this will change as we learn more.
More testing requires more information and resources. It has to be done regularly and with contact tracing. Most importantly, it needs to come with clear information about what test results mean and what they don’t mean.