Should You Get a COVID-19 Antibody Test?
You want to know if you have immunity to COVID-19. And now there are tests on the market—antibody tests—that promise to tell you if you were exposed to the novel coronavirus or had the disease. The hope is that these tests, if done in a widespread way, can offer clues on whether it’s safe to go back to work or relax social distancing measures, says Sandra Kesh, MD, Deputy Medical Director at Westmed Medical Group in Purchase, NY. The idea is that these could clarify who may be immune to the novel coronavirus, at least temporarily.
Widespread testing could not only just help you, but could help the community as a whole because it could give leaders a sense of the scope of the disease and a sense of whether there’s any sort of herd immunity—information that’s unknown right now.
So should you run to your local urgent care to get one? Head over to one of those tents in a parking lot that test you on-the-spot?
Before you hop in your car to go (does it even start anymore?), there are some basics you should know, because experts suggest these aren’t as promising yet as they sound.
In fact, while a number of tests are out in the marketplace and being used right now, none of them are FDA approved yet. The reason the tests are out in the marketplace and being used right now is because of an order granting a provisional FDA approval for these tests to be done. Currently, according to the FDA, there are four tests that have been given emergency use authorizations (EUA). That means unapproved tests can be used in emergencies, especially when there aren’t any approved alternatives.
Here’s what to know about these tests:
What is an antibody test?
These blood tests, also called serologic tests, measure IgG and IgM antibodies, which your body produces in response to an infection with the novel coronavirus. “Antibodies are what allow us to have protection against reinfection from a virus,” says Jake Deutsch, MD, co-founder and clinical director of Cure Urgent Care in New York City.
How is an antibody test done?
There are two types of tests. The first is a serum blood test, which involves drawing your blood. The second is a finger prick test, which is a point-of-care test. Basically, it means the test is done and results are given to you on the spot. Think drive-through testing sites that feature a big tent in a parking lot.
What does an antibody test really tell you?
Ideally, a good antibody test could tell you who had a COVID-19 infection and who didn’t, says Dr. Kesh. It could reveal if someone was exposed to the novel coronavirus. (It does not diagnose you with the disease; you need a different type of test for that.)
How accurate are they?
This is the big problem. Experts are concerned that some tests will show that people have immunity when they do not. Part of the problem could be the test, another part of the problem could be the timing of the test, and then there’s an issue of how to really interpret the results.
? What to know about the finger-prick test
The least accurate test available at this time, experts say, is the finger-prick test. These only have 85% accuracy because they’re insensitive and there’s a lot of opportunity for user error, says Dr. Deutsch. (Your finger is pricked, the blood is sucked up into a test tube, dropped into a reagent solution, swirled around, and then sucked back up in that test tube—possibly contaminating the sample—and then it’s dropped onto a test strip.) “Rapid tests are inconsistent and user dependent,” he says, noting that he has given himself one and found it difficult as a medical professional to do so.
? What to know about the serum test
This type, at least as far as the current options on the market, isn’t foolproof, either.
To tell you want you want to know, the test has to be well timed. Were you just sick? “If you check for antibodies too early (up to 10 days after the infection starts) you may get a false negative result, as your body didn’t have enough time to make a measurable level of antibodies,” says Dr. Kesh.
The test also has to be sensitive enough to be able to tell which coronavirus you were exposed to—there are four other types of coronaviruses circulating around (including types that cause the common cold). If you were to get an antibody test, you want one that is specific enough to detect if you are immune to SARS-COV-2, which causes COVID-19—not just any one of the coronaviruses that causes colds. Serum blood tests are more likely to be able to tell you this than finger-prick ones are.
Adding to the complexity is the fact that there is not yet enough data available to know what antibody level is necessary to confer immunity, says Dr. Kesh. A test can tell you that you have antibodies—but do you have enough to fight the virus and confer immunity?
Another wrinkle: Whether immunity for yourself means you can’t spread an infection to others. The jury’s still out on that.
I tested positive for the antibodies, does that mean I’m immune forever?
Experts don’t know yet. Once you get a test that the FDA stamps its approval on (which would ensure that you have the most accurate results in hand), “you can relax a bit. We don’t know exactly for how long, but, as with most of these viruses, immunity lasts for at least several months,” says Dr. Kesh. But we don’t have that test yet.
What you have to assume if you do get a test that even if you do have antibodies and the test was accurate, you are only immune for now. You still would need to get a vaccine once one comes out, says Dr. Kesh.
The bottom line on whether you should get an antibody test
“Here’s what I tell my family and friends: Call your doctor,” says Dr. Kesh. Ask the office if they’re recommending a specific test for patients. Dr. Deutsch believes in the test he offers patients, noting that it’s 97% accurate in detecting that there are antibodies to the virus in the sample. Your insurance may cover the test (although you’d still need to pay your co-pay or co-insurance). Always ask your doctor or urgent care facility about your own coverage options. Of course, going into a facility could potentially expose you to the virus, so Dr. Deutsch urges people to pre-register rather than walk in to reduce wait times.
Dr. Kesh’s office tells patients that when they have an antibody test they recommend, they’ll make it available. “The worst thing would be to get false reassurance that you’re immune and relax,” she says.
But things are changing fast, and Dr. Kesh expects the FDA to back a test soon.
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