As we are now past the one-year mark of living with the coronavirus, and even with the vaccination program in full swing, testing is still useful for diagnosing and containing the virus. There are two specific forms of Covid-19 test, PCR, or antigen tests, designed to diagnose whether you currently have Covid-19 and antibody tests that are designed to detect if you have had it in the past.
Each of these tests differs from one another in terms of reliability and accuracy and have different aims. To help you understand these different coronavirus tests, we are going to highlight five things you definitely need to know about them.
Specificity and Sensitivity are Used as Measuring Usefulness of Tests
There are two different measures are used for determining the credibility of tests. Basically, how well does it detect the absence of virus and how well does it detect the virus. The sensitivity of Covid-19 tests is defined by the number of patients who correctly get positive results. Although specificity is defined by the number of patients who do not have the virus and get a negative result.
Generally speaking, the more sensitive tests have lower false-negative rates but have the risk of producing false positives if it does not have a high level of specificity. Whereas, highly specific tests may be more likely to produce false negatives if it is not sensitive enough, but will have a much lower false-positive result rate. PCR Tests are generally believed to be the gold standard as they are both highly specific and highly sensitive.
Antigen and PCR Tests are Different
Although they are often bundled together, because they are both diagnostic tests, antigen and PCR tests are different. PCR tests are used to find genetic material known as RNA that gives the coronavirus instructions to make the proteins that antigen tests look for.
Both are administered via a swab from the back of your throat or nose. How they are treated in the lab is where most differences are. With PCR tests, a sample is sent to the lab and it is heated and then cooled using reagents that convert the RNA of the virus into DNA and then produce lots of copies. This enables the lab to identify the organism. This can take hours, uses highly sophisticated equipment and specially trained technicians and just one sample is done at a time.
Antigen tests, in contrast, are referred to as rapid tests, work involve mixing the swab sample with a special solution that extracts specific proteins found in the virus. The combined liquid is then put onto a paper strip with a special antibody designed to bind these proteins when, and if, they are found. This test has an advantage in that it doesn’t need a lab and only takes 30 minutes to complete. The downside that speed is a trade-off in sensitivity.
Antibody Tests Could Be Used Measuring Vaccine Response Durability
The immune system deploys antibodies as a response to foreign invaders, like the coronavirus. The curious thing is testing positive for viral antibodies only tells you you’ve had the virus in the past. It is believed though, that the tests could be used to estimate the spread on a population level, such as how much of the population and the specific ethnic groups that have contracted the disease, in addition to measuring vaccine response durability.
Negative Results from Rapid Tests Do Not Mean You Are In the Clear
Although governments like using rapid testing, as they are quicker and cheaper to deploy, they offer less accuracy. Therefore, it is not a good idea for negative results from these tests to be used to validate taking part in what would be considered risky activities like meeting up with vulnerable/at-risk and elderly relatives.
The Rapid Test Administer Can be Crucial to How Effective They Are
Although there are at-work and at-home kits available, it is thought that if you want accurate results from rapid tests like lateral flow tests, the test should be administered by a professional or trained individual.
As PCR tests are only processed in labs, they are much less likely to be inaccurate.