The Right Test To Beat COVID 19
The City of Greenville, South Carolina, along with Prisma Health, Bons Secours Health System, and the South Carolina Department of Health and Environmental Control, recently held a news conference to sound the alarm about a spike in COVID 19 infection. Officials emphasized that wearing masks and social distancing are within everyone’s control and essential to slowing the spread of the disease. Unfortunately, the Greenville News subsequently reported that new coronavirus cases in South Carolina rose 18.7%.
Mask wearing and social distancing are important, and so is testing. One of the most challenging aspects of COVID 19 is that it can be spread by infected people without disease symptoms who unknowingly infect family members, co-workers, fellow students and church members, and others they come in contact with.
SC DHEC recently increased the level of COVID 19 testing in South Carolina, relying solely on a laboratory test known as RT-PCR. After a nasal or saliva sample is collected from an individual, this test identifies virus DNA in the sample to indicate the individual is infected. Health professionals agree that this is the best laboratory test for diagnosing if an individual is infected.
Many public health experts, including Harvard Epidemiologist Dr. Michael Mina and Dr. Harold Varmus, M.D., former director of the National Institutes of Health and a Nobel Prize winner, are sounding the alarm that RT-PCR tests are not the most effective way to screen a population for who is contagious and likely to spread the disease to others. RT-PCR tests have three significant disadvantages as health screening tests. First, they are expensive, typically costing from $80 to $120 per test, because they require trained professionals working in laboratories. This limits the number of people who can be tested. Second, they can detect the DNA from dead virus and provide a positive test result after an individual is no longer contagious. Third and most importantly, there can be a delay of 24 to 48 hours in getting a sample to a laboratory for processing and reporting an individual is infected. Many people tested experience even longer delays. In addition, individuals not infected on the day of the test may become infected during the delay. In either case, during the delay infected individuals may not isolate and risk infecting other people.
A different kind of test, an antigen test, has been used for years in health screening of other infectious diseases. An antigen is any substance foreign to the body, like a virus, that causes the immune system to produce antibodies against it. COVID 19 antigen tests, currently being used in Europe and elsewhere, detect proteins of live virus. Relative to RT-PCR tests, antigen tests are much less expensive, as low as $5 per test, so many more people can be tested. They typically do not report positive when individuals have dead virus and are no longer contagious. Most importantly, antigen test results are available within a few minutes, so individuals who are contagious can isolate immediately so they do not infect others.
There is a downside to antigen tests relative to RT-PCR tests. Antigen tests do not detect that someone is infected in the first few days of infection when the amount of virus in the body is low, as RT-PCR tests do. This is why RT-PCR tests are the standard for clinical diagnosis of infection. Antigen tests are effective when the amount of virus in the body grows and an individual becomes more contagious, which is why they are good health screening tests. Antigen tests can overcome the problem of not identifying early infection by more frequent, inexpensive testing. Antigen tests are also appropriate to screen individuals on the day of sporting events, church activities, and other mass events to minimize the chance of contagious people attending and infecting others.
Leaders in government agencies, businesses, educational institutions, not-for-profits and elsewhere, are all seeking to keep their populations safe during this pandemic. It is important to select the right tool for the job to be done. To diagnose if an individual is infected with COVID 19, a RT-PCR test is the best test. If the goal is to slow the spread of COVID 19, a low cost antigen test providing quick results to more people more frequently may be the right tool for the job.
These are crazy times. We all need to be responsible. Wear masks. Stay socially distant when possible. Ask questions of leaders in our workplaces, our schools, and our communities about whether the right testing is being done to slow the spread of infection to keep us all safe and avoid shutting our community down again.
Contact John Warner at JohnWarner@AccessibleDiagnostics.com to learn more.
