It can be confusing, especially with so many testing options available these days. For example, if you’ve ever bought a pregnancy test, you know how many varieties there are. You can even buy them in bulk. But they all work pretty much the same way, so it’s more about choosing a brand that you prefer. But COVID tests are still pretty new to everyone, so you may still be feeling your way around how they work. So how do you choose which COVID test to go with? Consider the benefits of the various options that are available to you.
Two types of COVID tests
There are two basic categories of COVID tests: diagnostic tests and antibody tests. A diagnostic test will show whether or not you have an active infection with COVID. This is the kind of test you want to get if you think you’ve been exposed to COVID or you’ve started developing symptoms. This is also the kind of test you want to get if you need to have proof of your negative COVID status. In contrast to the diagnostic tests, an antibody test will detect the presence of antibodies in your blood that your body has produced in response to SARS-CoV-2. But you don’t want to get an antibody test to see if you’ve come down with an active case of COVID because those antibodies can linger in your bloodstream for weeks, or even months, after you’ve had an infection and recovered.
A closer look at diagnostic tests
Within the category of diagnostic tests, you have the rapid antigen test and the polymerase chain reaction (PCR) test. Whichever diagnostic test you go with, here’s something to take to heart. “It’s important to remember that getting a good nasal swab sample is also important,” says Dr. Sharon Nachman, MD, chief of the division of pediatric infectious diseases at Stony Brook Children’s Hospital in New York. “And if the sample is not taken correctly, then the test result may also not be valid.”
Antigen test
Also known as the rapid antigen test, the antigen test looks for the presence of viral proteins from COVID. Specifically, it detects the SARS-CoV-2 nucleocapsid protein, which is the “most abundant protein expressed by the virus,” according to the COVID-19 Real-Time Learning Network established by the Infectious Diseases Society of America (IDSA) and the Centers for Disease Control and Prevention (CDC). If you’re experiencing symptoms of COVID, this test is a good option. That’s because it assesses for acute infection–that is this test can confirm if your symptoms are indeed a sign that you have COVID. And if you get a positive result, you can then take the appropriate steps to isolate and get treated while you’re recovering. Another advantage of the rapid antigen test: almost no waiting. You’ll get the results back quickly, hence the “rapid” in the name of the test. According to the CDC, most of the currently available tests will return a result to you in 15-30 minutes. Plus, there’s the convenience factor to consider. You can buy a rapid antigen test and do it yourself if you can’t get to a doctor’s office, urgent care center, or COVID testing location. Keeping a test on hand at home could be particularly helpful for people with transportation or mobility issues, or people who are immunocompromised and don’t want to venture out to get tested, says Dr. Carlos Malvestutto, MD, MPH, an infectious disease physician at The Ohio State University Wexner Medical Center. However, be forewarned that this type of test is less sensitive than a PCR test, so you could get a false negative result, says Dr. Malvestutto. He adds, “Some (rapid antigen tests) are pretty good, and others are not quite as good.” The antigen tests can be more variable in terms of accuracy, says Dr. Philip Felgner, PhD, director of the UCI Vaccine Research and Development Center at the University of California, Irvine.“So, it’s hard to make a blanket statement that antigen tests are better or worse than the PCR tests, because it depends on which antigen test you are using,” he says.
PCR test
Then you have the reverse-transcriptase polymerase chain reaction (RT-PCR) test, which many people just call the PCR test. These tests are part of a larger category of testing technologies known as molecular tests or nucleic acid amplification tests (NAATs), as they are looking for very small amounts of genetic material that’s unique to the COVID-19 virus, explains John Carlo, MD, member of the Texas Medical Association COVID-19 Task Force and CEO of Prism Health North Texas. “The PCR tests are obviously the gold standard because they’re the most sensitive and they’re also the most specific,” says Dr. Malvestutto. That means you can be confident with the result that you’ll receive from this type of test.“Because these tests look for unique genetic segments of the COVID-19 virus, it is very much like a fingerprint, so these tests tend to be very accurate,” says Dr. Carlo. According to the IDSA and CDC’s COVID-19 Real-Time Learning Network, “Typically the sensitivity of antigen tests is 30% to 40% lower than for RT-PCR, depending on whether subjects were symptomatic or asymptomatic.” However, this is not a situation for instant gratification. It may take longer to get your results back from a PCR test than with a rapid antigen test. You may have to wait a few hours or even a day or two, depending on where you get tested. Some healthcare facilities do offer point-of-care PCR testing with results that come back quickly, but you should ask and not assume that’s the case. “Rapid PCR tests are more expensive and are not very widely available at the moment,” says Dr. Carlo.
How antibody tests work
Unlike the diagnostic tests, a COVID antibody test is a blood test. Also, this type of test doesn’t measure or look for the COVID virus in your nasal mucus or sputum. Instead, this test looks for antibodies, which are proteins that your immune system produces in response to an infection, according to the Mayo Clinic. “Antibody tests measure whether you were previously exposed to the virus, or whether you were vaccinated and still have the antibody response to what is presented in the vaccine,” explains Dr. Felgner. It takes several weeks for your body to develop enough antibodies for the test to detect. An antibody test might even detect antibodies from an asymptomatic infection that you never knew you had, according to the CDC. And you could have antibodies in your bloodstream for months after recovering from a COVID infection. For these reasons, experts wouldn’t advise you to seek out an antibody test to diagnose a current infection with COVID. Go with a rapid antigen or PCR test instead. Next up: We Might Have to Live With COVID Forever—Here’s What That Will Look Like
Sources
John Carlo, MD. CEO of Prism Health North Texas.Philip Felgner, PhD. Director of the UCI Vaccine Research and Development Center. UCI.Carlos Malvestutto, MD, MPH. Infectious disease physician, The Ohio State University Wexner Medical Center.Sharon Nachman, MD. Pediatric infectious disease expert, Stony Brook Children’s Hospital.COVID-19 Antibody Testing. Mayo Clinic.Interim Guidance for Antigen Testing for SARS-CoV-2. CDC.Rapid Testing. IDSA and CDC.Test for Past Infection. CDC.
