Antibody tests for COVID-19 were originally touted as a way to help get people back to normal life, but now experts aren’t so sure.
“We’re in very early and very confused days with antibody testing,” Dr. William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Yahoo Life. A lot of it is because the Food and Drug Administration (FDA) allowed companies back in March to put antibody tests on the market at a pace that is faster than usual and under less strict regulations, he says. Under the FDA’s Emergency Use Authorization (EUA) policy, companies evaluated the tests themselves and notified the FDA of their findings. Typically, the FDA evaluates tests as well before they go on the market.
“The problem is that these are tests that need to be validated and calibrated, and many of the tests out there don’t do that. So even though you hear about companies flooding the market with these antibody tests, a lot of them are not validated,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said on “Good Morning America” on April 20.
So, there are tests out there — they’re just not all entirely accurate. Still, there is a way to undergo an antibody test right now, and maybe even to get fairly accurate results. Here’s what you need to know.
How does an antibody test work?
An antibody test, aka a serological test, detects the level of antibodies or proteins in blood when the body responds to a specific infection, like COVID-19, the FDA explains. The test focuses on the body’s immune response to the infection vs. the virus itself.
The test isn’t necessarily great at detecting COVID-19 in its early stages, though. When you first contract the virus, your body’s immune response is still building and the antibodies might not be detected yet, the FDA says.
What are the different types of tests available?
Right now, the tests fall into two basic camps: a finger prick and a blood draw, infectious disease expert Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Life.
With the finger prick test, which is called a lateral blood flow test, blood is collected with a thin straw and put on a cartridge with a solution that will cause a reaction. “You might even get a readout within a few minutes,” Schaffner says. “That’s a very attractive notion.”
The other test is a more traditional blood draw, Adalja says. This is called an enzyme-linked immunoassay (ELISA) test, which uses a blood sample and tries to link a particular antibody to a specific enzyme, a complex protein that causes a specific chemical change in the body, per Medline Plus. If the targeted antibody is in the test, the test will turn a different color. “An ELISA test is a standard way that we do antibody tests,” Adalja says. “It’s more complicated than just looking for antibodies. The antibody in the blood has to bind to something in the test.”
Which test is the most accurate?
It’s hard to say at this point. A new research project called the COVID-19 Testing Project, which featured a multidisciplinary team of researchers and physicians at the University of California, San Francisco, and UC Berkeley, among others, independently tested 14 antibody tests — both the finger prick and blood draw tests. Of those 14, only three had reliable results. Some tests gave false-positive readings up to 16 percent of the time, and even the best tests detected antibodies in people who had been infected with COVID-19 only 90 percent of the time.
“What some people forget is there are other coronaviruses that circulate like influenza, RSV and rhinoviruses. Those coronaviruses can induce an immune response that can give you cross-reactive antibodies to SARS-CoV-2, the virus that causes COVID-19,” Dr. Pedro Piedra, professor of molecular virology and microbiology at the Baylor College of Medicine, tells Yahoo Life. “You have to be aware of that because it can sometimes confuse the matter to whether you were infected with SARS-CoV-2 or something else.”
Many of the new tests that are hitting the market are finger prick tests, Schaffner says, and he’s wary of these. “The validity of these lateral flow tests has yet to be determined,” he says.
And, while the ELISA test is the most commonly used type of test for antibody testing, that doesn’t automatically mean it’s accurate for COVID-19. “It’s not necessarily more reliable, it’s just a more intricate process than a regular test where you’re just looking for antibodies,” Adalja says.
So, which tests are FDA approved?
The FDA originally authorized one EUA for an antibody test, made by Cellex, to be used in clinical labs. Since then, the organization has granted EUAs to 50 different tests. (You can find the full list on the organization’s website.)
These tests weren’t granted FDA approval in the traditional sense, and the FDA has gotten criticism for allowing so many tests to hit the market without independently evaluating their effectiveness. “The FDA is now doubling back, but it’s unclear what they’re going to do with the tests that are already on the market,” Schaffner says.
How can you get tested?
It’s possible to go to your doctor and get a prescription for a test, Adalja says. “There are kits out there—availability just varies,” he says. Select health centers and hospitals across the country are also offering tests, he adds. You’ll just want to call in advance to make sure an organization near you offers a test, and that it’s still available.
Should you pay to get tested?
Some private labs will allow you to get an antibody test, either with or without a prescription from your doctor. Currently, places like the National Jewish Health Center in Denver and Innovative Express Care in Chicago are offering tests, but it will cost you. For example, the National Jewish Health Center’s test is $94, and Innovative Express Care’s is $250.
As of right now, experts say you shouldn’t be scrambling to get one of these tests. “I can’t recommend a particular test right now,” Piedra says. “You have to be able to rely on a test that will give you consistently good results and we don’t have that yet.” Schaffner agrees. “I wouldn’t recommend anybody get tested at the present time because there are a lot of questions about these tests that need to be answered,” he says.
When should you get tested?
If you still want to get tested, Schaffner recommends that you wait at least two weeks until after you’ve recovered from either a confirmed case of COVID-19 or an illness that you thought might have been COVID-19. At that point, he says, you should have developed antibodies that can be detected by a test.
Overall, experts stress that we’re not quite there yet with antibody testing — but we will be. “There are many academic centers and companies that are trying to develop very specific, sensitive tests,” Piedra says. “But these take time to generate. They will come.”
For the latest coronavirus news and updates, follow along at https://news.yahoo.com/coronavirus. According to experts, people over 60 and those who are immunocompromised continue to be the most at risk. If you have questions, please reference the CDC’s and WHO’s resource guides.
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