Now that there are so many options for COVID testing available to the consumer, how do you know which one you need so that you are getting an accurate result without wasting your time and money? The answer depends upon what you need the test for—which can range from personal peace of mind to on-the-job screening to international travel, and there could be a different test preference for each unique need. Let’s walk through each type of test and we’ll give you our recommendation for when each is most appropriate.
When the pandemic first started, one of the only types of tests available was the Reverse Transcriptase Polymerase Chain Reaction test, or RT-PCR. This is a laboratory-based test where scientists amplify DNA contents from a patient sample looking for virus. Scientists can do this for many types of viruses, but with COVID, they look for a particular part of the virus called the spike protein. This type of test not only can detect whether a virus is present, but it can also detect viral load, or how much virus is present in the sample. This type of test has the highest accuracy to detect the COVID virus. Importantly now that we have different variants circulating, the sample from this test can be examined further to determine which variant you may be infected with. Shannon likes to say “a PCR test is like picking a needle out of a haystack. If there is virus present, the PCR test can find it almost 100% of the time.” The downside of this test is that it is not rapid and can take several hours (and sometimes days as you may recall during the beginning of the pandemic) to return. It is also the most expensive type of test to run. This type of test is required however for certain surgical procedures and some countries require documentation with this type of test before allowing entrance to travelers. If you need an RT-PCR, you must ensure testing center you go to offers this type of test, and you want to schedule your appointment so that you get your results within the time frame required (i.e. within 72 hours of travel or procedure). By December 31 2021, the CDC had announced that it will withdraw the request for FDA granted Emergency Use Authorization for the assay that detects SARS-CoV-2 only. They are encouraging use of a multiplexed method which can facilitate detection of COVID as well as other respiratory viruses such as influenza. Such assays can save time and resources for patients who are experiencing symptoms. This may have impact on drive-through testing centers who are only testing for COVID-19.
Rapid tests are another testing option and are a good choice for detecting virus quickly. They are not as sophisticated as an RT-PCR, and may miss detecting virus, especially if the virus present is near a low threshold. But these tests are quite good at returning a positive result if a patient is contagious and has a higher viral load. Their main advantage is that they can deliver results quickly enough to help identify “positive” individuals from potentially spreading the virus to others. There are a couple of types of rapid tests available:
Rapid Molecular Tests
Rapid molecular tests use a particular technique that can detect presence of the SARS-Co-V-2 virus by recognizing coronavirus RNA from a patient’s sample. Results are available within 15 minutes with an accuracy that’s high (i.e. >96% accuracy with the Abbott ID Now test if the viral load is above the minimum threshold). There is a higher false negative rate than with RT-PCR, though, so a negative test on a rapid molecular test might not always mean you are truly negative. We often send off a confirmation RT-PCR with our rapid molecular tests to ensure accuracy. Rapid testing is a very important option, though, particularly because results are available with such quick turnaround, allowing someone to quickly go into isolation to reduce transmission. Some countries accept this type of testing for international travel, but they often require specific documentation that accompanies the test result for travel clearance. Our providers can help you receive the proper documentation if this is the type of test you need.
Rapid Antigen Tests
This test uses what’s called “lateral flow” technology to identify the presence of COVID-19 “antigen”, one or more of the protein molecules on the outside of the COVID-19 virus. The technology is the same as used for over-the-counter pregnancy tests, or similar to the tests doctors have used for years to check for Strep throat or mononucleosis. It results in rapid turnaround, usually less than 15 minutes, but these tests are not as accurate as those previously discussed (~85% able to detect viral presence when performed under strict conditions). At the beginning of the pandemic these types of tests originally received a bad reputation because of the inconsistencies with results. Technology and quality control have improved since then, and lateral flow tests are approaching a higher sensitivity and specificity, meaning a confident result. The lower-cost BinaxNOW test is among the most studied rapid antigen tests and demonstrates strong performance (~95.6% sensitivity in people seven days or less post-symptom onset who are most likely to be infectious and spread the virus to others).
Another type of testing is checking for antibodies, yet because antibodies don’t start to develop immediately, these tests are best after you’ve recovered from an illness with COVID. Both rapid and quantitative serum antibody tests are available. Rapid fingerstick tests are able to determine if a person has developed short and longer acting antibodies, but they don’t define the quantity of those antibodies present. Blood tests are able to detect the level of antibodies to both native virus and can separate the antibodies a person develops from the native virus from the vaccine.
ZüpMed was the first private clinic in the city of Memphis to offer testing for COVID-19.
We continue to provide the most accurate Coronavirus testing available with rapid turnaround and personalized consultation by licensed providers… every step of the way. We offer gold-standard RT-PCR testing with same- or next-day results, “rapid” in-room molecular testing with answers in as little as five minutes, and low-cost 15-minute COVID antigen tests. We also provide consistently reliable COVID antibody testing for both native infection and vaccination and will walk you through the sometimes-puzzling results.