The Truth About COVID-19 Antibody Testing

Experts say life can’t return to normal until we do more testing. But what exactly does that mean, anyway?

by Sarah Ellis Health Writer

In this strange new COVID-19 world, everyone is wondering: When will it all end? As lockdowns lift in different states, we all want to know when it'll be truly safe to return to work, school, and the fun activities of life.

The unsettling reality is that no one knows how long it will take for things to return to normal—and we won’t know until widespread testing is made available to confirm who’s positive out there, says Rashid Chotani, M.D., the vice president of Medical Affairs at CareLife Medical in Fairfax, VA. “Widespread testing is what enables us to discern disease incidence and prevalence, and to determine who has recovered from infection,” explains Dr. Chotani.

World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus shares this view. This spring, he tweeted: “One of the main things we've learned in the past months about COVID-19 is that the faster all cases are found, tested, isolated & cared for, the harder we make it for the virus to spread. This principle will save lives & mitigate the economic impact of the pandemic.”

Antibody testing may help do this and more. That’s because there is still so much to discover about the novel coronavirus (it has only been infecting humans since late last fall). Many researchers suspect that if it behaves like most other viruses do, the presence of post-infection antibodies in our bloodstreams may provide some level of immunity—and hopefully allow us to return to our regular lives.

What Are Antibodies, Anyway?

When you catch a virus, your body starts working immediately to counteract it. Your white blood cells produce proteins called antibodies in response to the infection, whose main job is to kick this "invader" out of your system. “The presence of an antibody indicates that someone has been exposed to that pathogen at some point,” says John Schmitz, Ph.D., associate director of the Clinical Microbiology/Immunology Laboratories at UNC Hospitals in Chapel Hill, NC.

Two types of antibodies in particular are important indicators for COVID-19. (They are produced in response to a variety of different infections—coronavirus is just one example.)

  • IgM (short for “immunoglobulin M”) indicates that someone was recently exposed or is currently fighting off an active infection.

  • IgG (you guessed it–“immunoglobulin G”) develops later on, and it shows that you’ve developed an immune response to the virus. Whereas IgM peaks and fades within a matter of weeks, IgG can sometimes last for months or even years to provide some level of protection from re-infection.

The level of protection these antibodies provide depends on the specific virus—and for COVID-19, scientists still aren’t sure whether immunity develops this way. But the hope is that these antibodies might indicate at least some level of protection against COVID-19, once someone has recovered from illness.

The important word there is might. On April 17th, Michael Ryan, M.D., executive director of the WHO Health Emergencies Program, warned that “nobody is sure whether someone with antibodies is fully protected against having the disease or being exposed again.” Scientists and health officials hope to know more in the coming months.

Why Is Antibody Testing Important?

In order to know if you have the antibodies for COVID-19, you need a test for them. Unlike polymerase chain reaction (PCR) nasal-swab testing, which tells you if you currently have COVID-19, antibody tests have the potential to tell us who has already recovered from the virus—even if such individuals never showed any symptoms, which occurs in at least 25% of all cases, according to the Centers for Disease Control and Prevention (CDC). This is especially important for us to learn to help stop community spread among people whose symptoms are so mild they might not know they have COVID-19 in the first place—but are continuing to engage with others, potentially transmitting the disease.

This is a really big deal. “The faster we can clear individuals from active disease state, the faster we can mitigate the socio-economic downturn and social disruption,“ explains Dr. Chotani. In other words, the more people we can test, the more experts will know about when it’s safe to reopen the economy again.

How Is the Antibody Test Done?

Karen Dukess, 57, is an author and mom of two living in New Rochelle, NY. She developed suspicious symptoms in early March, headed to Greenwich Hospital in Connecticut (under the instructions of her doctor) to do a drive-through test, and found out she was positive for COVID-19 on March 10.

Luckily, Dukess recovered at home within several weeks. She then immediately signed up to get her blood tested for antibodies at Mount Sinai Hospital in Manhattan. She arrived at the facility on April 2, where she was given a mask and got a temperature check at the door. “There were a lot of people there, two waiting rooms,” she remembers, describing how people were purposefully kept at a distance from one another.

Dukess got her blood drawn and did a PCR test, to make sure she no longer had an active infection. Two days later, she was informed that she did have resistant antibodies to COVID-19. But to her surprise, she also tested positive once again for COVID-19 through the nose swab, even though she no longer felt sick. One week later, on April 10, she returned to Mount Sinai for a final nose swab test to confirm the virus was no longer present in her RNA—and, finally, she tested negative. Which cleared her for the next step: donating her plasma.

What Is Convalescent Plasma, and Why Might It Help?

Plasma is the medical term for the golden-colored part of blood containing antibodies, and it’s important because scientists can use it to study the COVID-19 resistant antibodies from recovered patients. Again, at this time it’s unclear whether antibodies indicate immunity—and that’s what scientists are working around the clock to find out. Since such antibodies may hold the key to ending the coronavirus pandemic, survivors are being asked to donate blood or plasma for research purposes.

Whats more, the FDA is encouraging those who have recovered from COVID-19 to donate convalescent plasma in the hopes that it can be used to treat seriously ill patients, by reinjecting it into their bloodstreams to boost their immune response. When you donate plasma, a healthcare provider will draw your blood, put it into a machine to separate out the plasma, then reinject the rest of the blood back into your arm. This is still an experimental approach in the clinical trials stage, but it has been used successfully during other epidemics such as SARS, MERS, and H1N1.

Dukess is hoping to donate her plasma at Mount Sinai, but she’s still waiting to hear back for follow-up instructions. In the meantime, she responded to a request for blood donors from Rockefeller University in Manhattan to participate in a series of studies on prevention and treatment of the virus. Researchers at Rockefeller are looking for “elite neutralizers,” a fancy term for antibodies so resistant to COVID-19 that they could be used to make a drug. In other words, scientists believe that a small group of people may have battled the virus so effectively that their antibodies could help create a cure.

On April 17th, Dukess arrived at Rockefeller to donate blood. The campus was nearly empty. The nurses took her vitals, did a finger-prick hemoglobin test, and then drew about half a bag of blood. “It was frankly one of the most exciting days I’ve had in weeks, because I got to go somewhere and see so many people,” she says. “It felt good to do something useful.” She hopes her early experience with the virus can ultimately help keep other people safe.

Karen Dukess.
COVID-19 survivor Karen Dukess donating blood at Rockefeller Center in NYC on April 17. / Karen Dukess

Can I Become an Antibody Donor?

If you’re a recovered COVID-19 patient (or you believe you may have had the virus), you may be able to donate blood or plasma to help with research efforts. The FDA’s website provides information about where you can donate, and from there, you can contact a representative in your area.

New, antibody testing and experimental treatments hold some promise. “The ability to identify individuals who are IgM-negative and IgG-positive is critical if we are to return to some normalcy and reassure labor force mobility,” Dr. Chotani says. Schmitz’s team at UNC is currently working to figure out which model of antibody testing is most accurate and able to be used at high volume.

Should I Get an Antibody Test?

As antibody tests have become widely available in hospitals and walk-in clinics, and even offered by some frontline employers (like grocery stores), you may be eager to find out if you have COVID-19 antibodies—and if you do, whether that indicates immunity. Unfortunately, at this point, immunity is still a big unknown. Doctors just don't for certain that this virus behaves like similar ones. The CDC advises that until additional data is available, no one should change their social-distancing habits or use testing results to make life decisions (like a visiting an elderly relative, say, or returning to the office). That's because, even with antibodies present, not even the scientific community knows with this particular virus if immunity is given, or how long it might last.

Still, maybe you want to know if you've already been exposed to the disease, so you'd like to do a test to find out. There are nearly 200 different brands of antibody tests flooding the market right now, yet only 18 of them have received Emergency Use Approval from the FDA. (See those approved antibody tests here.) Of the 18, Schmitz notes that many are manufactured by companies that have produced highly accurate, if non-COVID-19-related, tests before, which is a good sign. However, others on the short list—not to mention the additional 175 or so test kits out there—were created by companies with no history of producing such tests. And accuracy results have been all over the map, with a documented surge of false results. So, the accuracy of the test you’re getting comes down to the specific brand of test your hospital or clinic is using.

"There is no reason that a test performed by a hospital lab versus a point-of-care site [walk-in clinic] would be inherently different," Schmitz says. "Rather, a difference in accuracy would more likely be due to the specific test used. Hospital-based labs will typically use very sensitive technologies to detect antibodies. A walk-in clinic would be more likely to use a rapid test."

Meaning, if your test is done by a hospital requiring a blood draw, like the test Dukess took, it may be more accurate than a finger-prick test done by a walk-in clinic. "May" being the operative word here, because, again, it all depends on the specific test your hospital uses.

According to the American Medical Association (AMA), most of remaining tests not among the 18 FDA-approved kits rely upon the manufacturer’s self-verification—meaning, there’s really no universal standard for assessing a test’s accuracy. “So many tests were rapidly developed early on that I am not surprised there was a large variation in accuracy,” Schmitz says. “We don’t know with certainty about the quality of the manufacturers of all the tests that have been marketed.” A false positive result could lead you to assume you’ve had COVID-19 when you haven’t, which could potentially put you—and others—in danger, should you eventually be exposed to the virus.

The AMA advises against individuals using antibody tests to make any assumptions about their health or futures, a point echoed by Schmitz. “The utility of an antibody test for an individual is very limited,” he says. “Antibody tests should not be used as the sole laboratory test to diagnose SARS-CoV-2 infection.” For now, he explains, antibody tests are best used by researchers to screen plasma donors and to conduct studies about general population exposure. As for individual immunity? Only more consistent and accurate testing, plus the science to show that antibodies actually deliver a degree of protection, can prove you have it.

  • Mount Sinai Antibody Testing: Mount Sinai. (2020.) “Mount Sinai Developing an ‘End-to-End’ Diagnostics Solution for COVID-19 That Incorporates Diagnosis, Treatment Selection, and Monitoring of Disease Control.”

  • Mount Sinai FDA Approval: Mount Sinai. (2020.) “Mount Sinai’s Blood Test to Detect Antibodies to COVID-19 Receives Emergency Use Authorization From U.S. Food and Drug Administration.”

  • Convalescent Plasma COVID-19 Clinical Trials: Proceedings of the National Academy of Sciences of the United States of America. (2020.) “Effectiveness of convalescent plasma therapy in severe COVID-19 patients.”

  • FDA Plasma Donation: U.S. Food and Drug Administration. (2020.) “Donate COVID-19 Plasma.” fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/donate-covid-19-plasma

  • FDA Convalescent Plasma Research: U.S. Food and Drug Administration. (2020.) “Recommendations for Investigational COVID-19 Convalescent Plasma.” fda.gov/vaccines-blood-biologics/investigational-new-drug-ind-or-device-exemption-ide-process-cber/recommendations-investigational-covid-19-convalescent-plasma

  • Rockefeller University Antibody Study: Rockefeller University. (2020.) “Scientists are using 'elite' antibodies from COVID-19 survivors to develop potent therapies.”

Sarah Ellis
Meet Our Writer
Sarah Ellis

Sarah Ellis is a wellness and culture writer who covers everything from contraceptive access to chronic health conditions to fitness trends. She is originally from Nashville, Tennessee and currently resides in NYC. She has written for Elite Daily, Greatist, mindbodygreen and others. When she’s not writing, Sarah loves distance running, vegan food, and getting the most out of her library card.