The Different Types of COVID Testing
Since the first wave of the rampant spread of COVID-19, we slowly come to learn more about the coronavirus pandemic and the steps we need to take to effectively control the outbreak. These steps include prevention measures such as handwashing and social distancing, widespread testing, and contact tracing. This is especially important with the looming second wave. We also made great breakthroughs and progress on the COVID-19 vaccine with Pfizer-BioNtech and Moderna achieving great success in their Phase 3 studies. In addition to all these amazing successes, we also learned a lot more on testing patients for COVID. There are currently two primary types of COVID-19 tests. They are the diagnostic tests that look for current coronavirus infection in our mucus or saliva, and blood tests that test for antibodies, which look for past coronavirus infection.
Currently, the FDA has granted emergency use authorization to a COVID-19 test that can be obtained without a doctor’s prescription and can be performed completely at home. The Ellume COVID-19 Home Test is approved for use in adults and children above age 2 and older, regardless or not they present COVID-19 symptoms. The process involves using a nasal swab, stirring it in a vial of processing fluid, and then placing a drop of the fluid in an analyzer. This device detects coronavirus antigens and delivers a positive or negative test result within 20 minutes. There are a couple of other ways to detect SARS-CoV-2 (Shmerling).
Antigen Testing:
Antigen testing is usually conducted via nasal swabs or throat swabs. The majority of rapid diagnostic tests have been antigen tests and they are usually used to identify a person who is at or near peak infection. Antigen tests look for a piece of the coating of the virus. While they are cheaper and faster, there is a bit of a lag time between when someone gets infected and when antigens show up. Thus, if an infected person is not at peak infection, but is still contagious, the tests may come back negative. Additionally, false negative results tend to occur more often with antigen tests when compared to molecular tests. Thus, they are not as favored by the FDA as the single test for active infection.
Molecular Testing:
Molecular testing (also called PCR tests, viral RNA tests, nucleic acid tests) is usually conducted via nasal swabs, throat swabs, and saliva test. Polymerase chain reaction (PCR) usually serves as the mainstay of COVID-19 diagnostic testing; it is the lab technique used to detect the virus’s genetic material, more specifically the RNA of the coronavirus. While PCR tests are considered to be the most sensitive for detecting an active infection, they may also be too sensitive as it can still detect the virus’ genetic material even after a patient has recovered from the coronavirus and is no longer contagious (Duncan). Fortunately, the false positive rate (the possibility of a result that appears positive when it should not) is close to 0%. Overall, a molecular test via nasal swabs, throat swabs, and saliva test are highly accurate and it is usually used as a diagnostic COVID-19 test.
Antibody Testing:
Antibody testing is usually conducted using a blood sample. These blood tests can identify antibodies that our immune system produced in response to the infection. While it can not accurately tell us if we have a current infection, it can identify past infection. However, having an antibody test too early can lead to false negative results as it takes a few weeks for our immune system to produce antibodies to fight off the infection.
While we have learned a lot about the coronavirus, it is still a novel virus and there is still much to be uncovered. If you experience COVID like symptoms (fever, cough, shortness of breath, fatigue, muscle or body aches, etc.), it is important to self isolate and contact your doctor to determine whether or not your COVID-19 test is positive or negative. However, even if you aren’t positive, it is still important to continue to adhere to standard preventative measures such as social distancing, wearing a mask, and handwashing. By continuing these preventative measures and widespread testing, we can slow the spread and hopefully eventually eliminate the COVID-19 pandemic.
References:
https://www.health.harvard.edu/diseases-and-conditions/coronavirus-resource-center
https://www.health.harvard.edu/blog/which-test-is-best-for-covid-19-2020081020734
https://health.ucdavis.edu/health-news/newsroom/different-types-of-covid-19-tests-explained/2020/11
https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html
https://www.health.com/condition/infectious-diseases/coronavirus/covid-19-test-types
https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html
