Since the start of the coronavirus (COVID-19) pandemic, testing has been a very hot topic. It’s hard for the average person, without a background in science, to keep up with all the testing terminology, and even more so with new developments and changes in public health guidelines. We asked Bayhealth Senior Director, Laboratory Services Chris Dukes BSMT(ASCP), MBA, to give a crash course to help us make sense of it all and better understand the differences between the COVID-19 tests out there and how they work.
The current tests that exist for COVID-19 can be broadly classified into two types: a viral detection test and an antibody test. A viral test detects whether someone has been infected with the virus. This is the kind of test that’s been used for months now and also may be called a diagnostic, molecular, genetic, RNA, or PCR test. PCR refers to polymerase chain reaction, the technology which amplifies genetic material of the virus if present in a sample. Samples are collected from the nose or throat using a swab. More recently-released PCR tests can be performed on a saliva sample.
In general, PCR tests are considered the more accurate and reliable kind of COVID-19 tests, said Dukes. Because most require trained healthcare workers to collect samples and trained lab technicians to process the tests using specialized supplies and instruments, all these factors have a bearing on the overall availability. Generally, results from a PCR test take days (and weeks, when there were previous severe backlogs across the country).
The latest viral tests on the market are antigen tests which quickly detect fragments of surface proteins on the spikes of the virus. While antigen tests are cheaper to produce and more easily administered, they are less sensitive than a PCR test. There are a few kinds of viral tests that produce more rapid results, either as point-of-care, meaning they’re done in a patient care setting, or performed in labs with special technology, but their use is often limited, and kits from some makers have been found to be less accurate.
The second major category of COVID-19 testing we’re hearing about is antibody testing, also known as serological tests. Rather than testing for a current infection, these look for the antibodies that show up 1-3 weeks after the body’s immune system has started to fight off the virus. This is done through a blood sample, typically through a simple finger prick.
Dukes explained that there are two main types of antibodies and most of these tests detect both. “One antibody, immunoglobulin M (IgM), is an indicator of a recent or active infection. Immunoglobulin G (IgG), on the other hand, shows previous exposure to the virus and may indicate some degree of immunity, but it’s not yet known if it’s true immunity and if so, how long it lasts,” he said. “With some kits, a positive tends to be a true positive but a negative doesn’t necessarily mean a person doesn’t have COVID. It could mean their body just hasn’t started making the antibodies that the test detects.”
With the rapidly changing landscape of the COVID-19 outbreak and the intense testing demand, the U.S. Food and Drug Administration (FDA) has allowed the sale of hundreds of products for antibody testing without review or approval by them. “As you can imagine, the performance of these tests can vary greatly,” said Dukes.
Aside from what test kits have been manufactured and are on the market, access to the various types of testing is a whole different element. There is wide variation from state to state, and in some cases, between healthcare settings, as to what testing is being used, based on what’s available and the criteria that has been set. Vice President of Ancillary and Clinical Services Brad D. Kirkes, MBA, MHA, OTR/L, CHT, FACHE, said that Bayhealth and other hospital systems in Delaware have worked with the Department of Public Health to align testing methods. “This means that if we use an antibody test, we will all follow the same algorithm related to consistency of testing. This also holds true for the PCR tests,” said Kirkes. “I am proud that as a state, the hospitals aligned early on in the COVID outbreak to ensure we were consistent in testing methods and practices across all hospital systems where testing was being performed.”
If you’re experiencing COVID-19 related symptoms or have been exposed to someone who has tested positive for the virus, contact your primary care provider or Bayhealth’s Coronavirus Management Team (CMT) at 302-310-8477 so a medical professional can guide you appropriately on the next steps you should take. Visit Bayhealth.org/COVID-19 to learn more.