COVID-19 Tests in Plain English
Are you exhausted with COVID-19 (aka COVID, SARS-2, The Virus, Coronavirus, The ‘Rona)? Yeah, you’re not alone. We are all exhausted. But we must stay informed about COVID-19 to get us through these times.
Today, we’re going to be talking about COVID-19 testing, specifically what each test is, why might each be used and what the results mean in plain English. Yours truly has spent a lot of her life as a biologist in the medical diagnostic industry…not just an MDBox Mamma.
There are three main tests at the moment: Antibody, Antigen, and Molecular (aka PCR).
But first, we need to do a little COVID-term-housekeeping:
COVID-19: Coronavirus Infectious Disease 2019 is the actual disease people suffer from
SARS-CoV-2: Severe Acute Respiratory Syndrome Coronavirus 2 is the virus that causes COVID-19. *
Epidemic: is a disease that affects several people in a specific region or community
Pandemic: is an epidemic that affects people in multiple regions and communities worldwide
Assay: fancy industry term for a medical test
Virus: a microbial entity that is technically not alive. Viruses consist of an outer protein shell and genetic material inside. It can only replicate inside a host cell.
RNA: Molecular genetic material (nucleic acid) like DNA but single-stranded. SARS-CoV-2 is an RNA virus; it is basically a spikey ball with RNA inside and proteins on the outside.
Serology: a test that looks for antibodies (aka antibody test)
EUA: Emergency Use Authorization. The FDA can deem something EUA to significantly reduce the regulatory hurdles to get something to market quickly. Most, if not all, SARS-CoV-2 tests are FDA EUA.
Rapid Test: A test that takes less than 30 minutes to complete from sample collection to result.
POC Test: Point of Care. A test that is run at the patient’s bedside in the hospital, in a doctor’s office or urgent care clinic.
PCR: Polymerase Chain Reaction, lab technique to make many copies of specific nucleic acid. Do you learn better by song, if so check this out: The PCR Song
Antibodies are what our body’s immune system makes to combat foreign substances (aka antigen—we’ll get into that next) like bacteria or viruses. Antibodies are our shape-shifting secret service force, not only are they made once they see an invader, they attack the suspect! They are made by B-lymphocytes, which are special white blood cells (WBCs). And yes, that is why you are tested for a white blood cell count when you might be really sick, in the hospital, or during your regular yearly physical. That count tells the doctor how strong your body is at defending itself. People with chronically low WBC counts are typically immunocompromised because they might have problems making antibodies.
Antibody tests detect antibodies your body has made to a foreign substance like SARS-CoV-2.
Now here’s a complicated (yet important) graph that I promise to demystify.
Antibodies are made once your body has encountered a foreign substance. Your body also needs time to make enough antibodies to combat whatever the nasty invader is. Therefore, antibody tests are not useful to detect the onset of an infection but better afterward. Here in this graph, you can see it takes one to two weeks to detect SARS-CoV-2 antibodies.
So why would you test for antibodies? Good question. It’s to identify people who have already been exposed and could be immune to a specific bacteria or virus for a certain amount of time. Unfortunately, with COVID-19, we still don’t know if we can become immune because we’ve only known him for less than a year.
Typically, these tests only need a drop or two of blood, and results are available within 10-15 minutes, and a trained person can visually read the results. Dozens of different manufacturers have made antibody tests that have FDA EUA.
Antigens are foreign substances that cause your body to create an immune response, which, as we learned, is the creation of antibodies. In the case of SARS-CoV-2, the antigen is the proteins that encapsulate the virus’s genetic material (aka nucleic acid, aka RNA).
And because I know you’re smart (because you chose to read this blog), you probably already figured out that an antigen test looks for the proteins of SARS-CoV-2. And yes, it’s that simple. See, you’re already an immunologist! 😉
Antigen tests start with a nasal swab sample, and results are available within 10-15 minutes. However, unlike antibody tests, there are only currently two antigen tests on the market with FDA EUA and usually require a machine that reads the test result. But don’t fret, several manufacturers are working on developing antigen tests that should be available later this summer and early fall.
Molecular (aka PCR) Tests
Molecular tests look for specific molecular material like DNA or RNA. SARS-CoV-2 PCR tests are looking for specific genes/ regions in the viral RNA.
A lot of the bodily fluid that is taken from you by a healthcare provider is used in molecular tests, especially if your doctor is trying to figure out if you have an infection. Just a couple of examples: respiratory, gastrointestinal, sexually transmitted infections are all identified by molecular tests.
Molecular tests are very sensitive (almost no false negative) and specific (almost no false positives). They can be run on machines (aka instruments) that process the test automatically in large volumes (or a batch). Almost all medical labs in the country have several machines from various manufacturers that run different types of tests. A rule of thumb with molecular tests: the larger the batch, the longer the result will take.
PCR is like a molecular photocopier. Molecular material is mixed with chemicals that help the copy process (like adding ink and paper to a copier). The mixture is subjected to several cycles of heating and cooling, which create more and more molecular material. PCR is almost always automated using equipment that just
automates the heating and cooling cycles to very expensive equipment that extracts the DNA from a sample, adds the chemicals, and reads the results (set it and forget it!).
Currently, there are over a hundred SARS-CoV-2 PCR tests with FDA EUA available.
And there you have it; you will be receiving your molecular immunology Ph.D.** in the mail. I hope you found this a little bit helpful in our current circumstances. If you have any questions, always feel free to reach out to us!
Love & Hugs-
* If you were cognizant in 2003, you might remember the first SARS epidemic. And yes, they are kissing-cousins. Over 8,000 people were infected by SARS-CoV globally, and almost 800 people died (10% mortality rate). SARS-CoV-2 is much more contagious yet less deadly (3.7% mortality rate) than the original.