There are several COVID-19 tests available on the market today! Are all COVID-19 tests created equal? How do governments and healthcare administrators decide which test to select to keep their citizens and employees safe? Through this article we will explain the common scientific metrics used to make this decision.
Test sensitivity is the measure of how well an individual test can detect viral protein or RNA molecules indicative of the virus. It reflects how often the test correctly generates a positive result for those who have COVID-19 (true positives). This metric is set to prevent false negatives, the case in which someone with the COVID-19 infection tests negative for it. For example, a test with 90% sensitivity is able to detect 90% of people with COVID-19 but returns a false
– negative for 10% of people with COVID-19.
Test Specificity is the measure of how well an individual test can detect the absence of viral protein or RNA molecules. In other words, how often a test returns a negative result for those tested that do not have COVID-19 (true negatives). This metric is to prevent false positives, which are positive results given to those who are not actually infected with virus. A test with 90% specificity will report false positives 10% of the time.
These metrics have a balanced relationship with one another, meaning when one of the two metrics is high, the other tends to fall short. For example, when the ability to receive positive results for those who do have the virus (test sensitivity) is higher, specificity tends to be lower, resulting in more false-positive results. On the other hand, when the test has a high percentage of specificity and tends to be better at ruling out those who do not have the virus accurately, it falls short in sensitivity, generating more false negatives.
Sensitivity and Specificity of COVID-19 Tests
RT-PCR/NAAT tests tend to have an analytical specificity and sensitivity above 95%, meaning they rarely give false results. These tests are highly specific because they use the unique genetic sequence of the COVID-19 virus, however, their sensitivity is affected by different factors. While timing of tests and sample collection impact sensitivity, their impression is negligible and does not nullify the results. At FastTest, all our testing is done under the strict supervision of healthcare professionals with years of experience. In other words, you have nothing to worry about.
Antigen tests tend to be less sensitive than RT-PCR/NAAT tests, meaning they result in more false-negatives. This is part of the consequence of being more affordable and having a far quicker (15 to 30 minute) turnaround time. The sensitivity is at its highest with antigen testing when the patient is at the peak of their viral load, within five days of their first symptoms. Due to its decreased sensitivity, antigen testing is not accepted for international travel certificates to most countries.
Ultimately, RT-PCR/NAAT tests have an incredibly high specificity and sensitivity rate compared to other tests. The RT-PCR/NAAT test is therefore the gold standard for COVID-19 testing used by governments around the world.