Because typical symptoms of COVID-19 infection are non-specific and overlap with other common viral illnesses, testing that can detect the virus specifically is very useful both for individuals and for public health.
The most sensitive and specific tests for COVID-19 are called PCR tests; these tests detect the nucleic acids (molecules like DNA) of the virus with a specificity and sensitivity that is generally around 98%. But, these tests typically take several hours to complete, and results are typically available within 1 to 3 days. Unfortunately, at present the demand for these tests has overwhelmed many laboratories delaying the resulting of tests as much as 10 days. More rapid “while you wait” tests are now available in many locations. These tests are typically not PCR tests. This type of testing now represents a significant proportion of the testing in the St. Louis region.
A word of caution is in order regarding some of the rapid testing: It is not as sensitive as PCR testing. This means that it is possible to have COVID-19 and to receive a test result that says that you do not have the virus. Various studies in the literature suggest that the “false negative” rate of rapid testing is often as high as 20-30%. There are many reasons why any kind of COVID-19 testing may be falsely negative, including the type of testing that is done.
If you have typical COVID-19 symptoms and receive a negative result from a rapid test, please follow up with a PCR test from a healthcare professional. In addition, seeking immediate or urgent care is always recommended whenever significant illness occurs or there is a rapid decline in someone’s condition.
The St. Louis County Department of Public Health has completed the process of reviewing a recent backlog of COVID-19 test results received from an urgent care company. The results have been added to our statistics page on stlcorona.com. As is our standard practice, each positive test result has been added to the total for the day that test was performed.
The Third Amended Order for Business and Individual Guidelines for Social Distancing and Re-Opening begins today, July 31 at 5:00pm. The order in its entirety can be found online here.