ABCs of COVID
Sometimes, all of these COVID terms feel like alphabet soup. We’re here to help clarify the science.
WHAT IS COVID-19
coronavirus: a family of viruses, many of which are similar to the common cold. When we think of COVID-19, we’re talking about a disease caused by a new coronavirus, SARS-CoV-2.
SARS-CoV-2: name for the novel coronavirus that was found in December 2019. Being infected SARS-CoV-2 can lead to the disease, which is called COVID-19, but you can be infected with SARS-CoV-2 without presenting symptoms of COVID-19. SARS-CoV-2 is an RNA virus, which means that the genetic material of the virus (RNA) cannot modify the genetic material of you as a human (DNA) because biological information does not flow in that direction.
COVID-19 TESTING
Diagnostic Testing: tests that detect parts of the SARS-CoV-2 virus that can be used to diagnose infection. The gold standard thus far for diagnostic testing has been a molecular test known as a PCR test.
Serology (Antibody) Testing: tests that detect antibodies to SARS-CoV-2 or measure an immune response to the virus. These tests cannot be used to diagnose a current infection. Part of this immune response includes work by your adaptive immune system to produce molecules specific to the invading virus; these molecules are known as antibodies and they fit pieces of the virus like an adjacent puzzle piece.
PCR or RT-PCR tests: This is a molecular test that tests a sample of respiratory material (often through a nasal swab) in a laboratory to look for genetic material (RNA) of SARS-CoV-2 using a lab technique called polymerase chain reaction (PCR). PCR tests are considered to be very accurate but take on average 1-2 days to get results.
- Note: RT-PCR tests can detect levels of the virus’ RNA that cannot be cultured, suggesting that the presence of a positive PCR test does not always indicate contagiousness (link)
- Polymerase chain reaction simply means than an enzyme called polymerase makes a lot of copies of the genetic material through a chain reaction so there is a strong enough signal to be able to detect the viral genetic material of interest
Antigen tests: unlike PCR, which looks for a virus’ RNA, antigen tests look for the presence of a protein, which typically implies current viral infection because when protein is detectable, the virus is typically “live” and transmissible to others (rather than detecting pieces of genetic material of the virus floating around that are essentially inactive). Because they often do not need a lab to be conducted, antigen tests are relatively inexpensive and can return results in 10-15 minutes.
IgM and IgG: Antibody tests often measure one or both types of antibodies called IgM and IgG. While similar, IgM antibodies are produced as a body’s first response to a new infection (short term protection). These antibodies often decrease as the IgG production begins. IgG antibodies are the most common antibodies and take time to form after a virus or infection; IgG antibodies remain detectable for longer periods.
Sensitivity and specificity: These terms are often collapsed into a singular term of just “accuracy.” Though they sound similar, they are actually different.
- Sensitivity: is the probability of getting a positive result if you are in fact positive. Therefore, a test that is highly sensitive means that there are few negative results that should in fact be positive, and thus fewer missed cases.
- Specificity: this is the probability of getting a negative result if you in fact do not have the disease. A highly specific test means that there are few false positives.
- Diagnostic test accuracy refers to the sum of all true positive and true negative results divided by the total number of all tests — in other words, the ability for a test to return the correct result, whatever that may be.
VACCINES
Spike protein (S protein): These proteins live on the surface of the virus. They are the proteins responsible for binding to other cells in your body. Most of the variant sthat are in the news mainly mutate in the virus’ S protein.
Nucleocapsid protein (N protein): The N protein is in the center of the virus and is responsible for the transcription and replication of the virus’ RNA. Many antigen tests, like the CareStart™ COVID-19 Antigen, detect presence of the N protein
mRNA vaccine: For COVID-19 this type of vaccine instructs our cells (through mRNA, or “messenger RNA”) to create harmless versions of the virus’ spike protein (S proteins). After that protein is made, the cell breaks the mRNA down and gets rid of it. Through this process, your body has learned how to recognize what a part of the S-protein looks like and if exposed to the real virus later, your body will recognize it and know how to fight it off. This technology has been developed for years in various academic institutions including the University of Pennsylvania and Harvard, despite the COVID-19 mRNA vaccines being the first approved vaccines of their kind.
CareStartTM COVID-19 Antigen tests are an accurate, American-made option for rapid testing. Learn more about how to purchase and implement serial rapid testing using this EUA-authorized tests.
The CareStart™ COVID-19 Antigen test has not been FDA cleared or approved. This test has been authorized by FDA under an EUA for use by authorized laboratories and at the Point of Care by medical professionals operating under a CLIA Certificate of Waiver, Certificate of Compliance, or Certificate of Accreditation.
Sources:
https://www.cedars-sinai.org/blog/covid-19-vocabulary.html
https://my.clevelandclinic.org/health/diagnostics/21462-covid-19-and-pcr-testing
https://www.merckmanuals.com/-/media/Manual/LabTests/ImmunoglobulinsIgAIgGIgM
https://www.health.ny.gov/diseases/chronic/discreen.htm
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html
