As we are entering what seems to be a second wave of the coronavirus outbreak, how should we approach getting tested and should we be relying on our results?
According to the article written by John Ingold of the Colorado Sun, there are many tests that are used to test traces of SARS-CoV-2 but knowing when and what you are taking is crucial to stop the spread. Covid-19 is a severe acute respiratory syndrome that has quickly caused a global pandemic. SARS-CoV-2 is a single stranded RNA-enveloped virus that contains spike proteins that allow viruses to penetrate host cells and cause infection. These spike proteins are divided up into two subunits, the S1 subunit and the S2 subunit. Once the S1 subunit binds to host cell receptors, two changes must occur for the S2 subunit to complete the fusion of the virus to the cell membrane. To test for coronavirus, the FDA has approved 170 different diagnostic tests and 47 blood tests for the virus. These tests are now being given out nationwide so they are more accessible to everyone but studies have questioned the accuracy of these tests. However, due to the numerous amounts of tests, it is crucial to know the differences and to learn which tests are right for your specific situations.
Blood Tests vs Diagnostic Tests
Blood tests, which are also called serological tests, test the blood for antibodies. Antibodies are indicators that your body has produced a immune response to the virus. The immune system protects the body against pathogens such as viruses and bacteria. In this case, the innate immunity is used to fight off Covid-19. Innate immunity is a defense that is active immediately upon infection. It is the first and second lines of defense and is a very rapid response. B cells within your body react to invading pathogens which causes the antibody to control the infection. These blood tests are usually used to test whether you have been previously infected by the virus but will occasionally detect whether you have the virus at that moment.
Diagnostic tests use other types of bodily fluids such as nasal mucus or saliva to test for an active infection. As you may have seen, they use long Q-tip swabs to swab the inside of your nose or mouth which they then send to a lab.
Sensitivity vs Specificity
When telling whether or not a test is accurate you must keep in mind the sensitivity and the specificity of the test.
Sensitivity tells whether or not the test is able to accurately detect the presence of an active virus. The less amount of sensitivity, the higher chance of receiving a false negative.
Specificity tells whether or not the test is able to accurately rule out the presence of an active virus. The less amount of specificity, the higher chance of receiving a false positive.
A guide to testing:
Antibody Tests: As stated previously, antibody tests tend to be more sensitive than they are specific. The FDA found that most antibody tests have sensitivity values near 100% but specificity values near mid-90’s. This leads to an increase in false positives. The FDA also found that in some antibody tests, the positive predicting values are under 60% which means that it is very possible that there is a 50% percent chance that you actually have them and a 50% chance you don’t. Ultimately, these tests are sometimes quite unreliable.
PCR Tests: The PCR test, polymerase chain reaction, is a test that searches for the virus’ genetic material. The PCR test increases the genetic material so that it reaches detectable levels. These tests are administered by Q-tip swaps and take a few days to process them. The PCR is considered the most accurate test available and many say that if you have symptoms or have been exposed, this is the test for you.
Rapid Tests: Rapid tests have become increasingly common as they are faster and more consumer-friendly. However, scientists warn people that they are best used to determine if your cold is actually a cold or if it is Covid-19. If you are asymptomatic, they suggest a PCR test. Emily Travanty, interim director of the Colorado Department of Public Health and Environment’s state and public health lab, warns that the rapid test is significantly less sensitive which in case may lead to false negatives.
Antigen Tests: Antigen tests for the virus by looking for which specific proteins are on the surface of the virus. These tests are highly specific so are unlikely to deliver false positives and more likely to give false negatives. If you are being tested repeatedly, antigen tests are the best for you. However, if you are only getting tested occasionally, you should get a PCR test in order to confirm your results.
By knowing which type of test you should get in your specific situation, you are helping the cause of stopping the spread. As we enter what many people are starting the call the “second wave” it is crucial to get tested constantly in order to protect those we love. (Note that if you have been exposed it is recommended to isolate for a week at home before getting tested as the the virus needs time to accumulate. Testing too rapidly will increase your chance of getting a false negative.)