Coronavirus (Covid-19) antibody tests: Do you really want one? Think hard about it. Maybe not.
Coronavirus testing: It has long been hard to get. Now suddenly in the New York area, tests are freely available.
The test will tell me truly if I have had coronavirus and am therefore immune, right? Or if I was exposed to the virus and magically skipped through, with few symptoms?
The expert opinions are in: Maybe. Maybe not.
We’ve been doing a lot of research about coronavirus (Covid-19), and particularly about testing. I live in the center of the pandemic. Also, I recently tested positive for coronavirus antibodies twice, and negative once, and I’ve been exploring what it means.
First: There are two kinds of tests. Both the respiratory test (nasal swab) and the antibody test have problems as far as accuracy. Beyond that, if the results are correct, experts disagree on what the results mean. If you have a positive respiratory test, that’s pretty clear: You’ve got it. But if you test negative, because of the high error rate, if you have with symptoms, most doctors will say you should still act like you have it. With the antibody test, same problem: Positive probably means positive, but false positives are clearly possible.
I asked Donald G. McNeil Jr., the star New York Times reporter, who’s a friend from long ago: Is this good news? Am I immune?
He said: “I would NOT trust that antibody test. There are about 50 tests, none are validated yet and we know that some give false positives if you have antibodies to the common cold coronaviruses. Also, we don’t know what level of antibodies confers immunity. So although it’s potentially good news, I would not assume you are immune. Better tests are on the way.”
My negative test from CityMD followed two positive tests, one from the New York State Department of Health, see here, and one at Stony Brook University Medical Center, see here.
Here’s a negative test from Go Health urgent care, partnered with Northwell Health, from a friend.
The ‘immunity passport’ idea — not so fast
For a while, Gov. Andrew Cuomo of New York and others were talking about using antibody testing as a way to give people an “immunity passport.”
“At the time Cuomo talked up antibody testing, using the procedure to establish immunity was widely perceived as a possibility,” Anna Gronewold and Shannon Young wrote over at Politico on May 5. “But that ambition quickly turned to disappointment as the World Health Organization came out against such strategies, saying there is no evidence that antibodies give immunity. Something that seemed to have been a silver bullet was too good to be true. Cuomo stepped back.”
There are several issues: Does the test (and there are about 170 on the market, of varying degrees of usefulness) actually sense the presence of the actual coronavirus implicated in Covid-19? And does presence of those antibodies confirm immunity? Depends on who you listen to, but the smart money is on “Maybe.”
The situation is changing quickly, also.
On April 20, Anthony Fauci told “Good Morning America,” ‘“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.
“There’s an assumption — a reasonable assumption — that when you have an antibody that you are protected against reinfection, but that has not been proven for this particular virus. It’s true for other viruses,” he said.”
Testing the tests
Then a team of scientists reported that they had tested the tests. “These tests are crucial to reopening the economy, but public health experts have raised urgent concerns about their quality,” The New York Times reported on April 24. “The new research, completed just days ago and posted online Friday, confirmed some of those fears: Of the 14 tests, only three delivered consistently reliable results. Even the best had some flaws.”
The scientists who started the test of the tests described the testing environment as “the Wild West.”
The FDA has given “emergency use authorization” to a number of tests, though the FDA’s “approval process” is deeply flawed. Dozens of other tests are being used, even without that light approval. The underlying scientific data on test performance is here. But remember, these are self-reported to the FDA and there hasn’t been enough time to really confirm performance.
What the doctors say
One of my friends asked her pediatrician about the tests; the pediatrician responded with this cautionary note from the Westchester, N.Y., county executive warning against using such testing to make personal decisions about exposure to coronavirus.
At one local Westchester medical group, a friend seeking to schedule a test heard from the nurse, “They will do it but the nurse told him that it is not reliable, as her husband and in-laws had the virus and she was exposed to it and not one of them tested positive for antibodies.”
Another friend had a test at CityMD in New York, after she had a serious bout of respiratory illness. The test came back negative — and she said a friend in the medical profession ridiculed her for seeking a test.
So, after a long time when no one could get tested, now every doctor’s office and a number of national labs have begun to offer these tests. See details here. But at many of these medical offices, the offer comes with a warning.
It’s logical to ask: why is my medical group offering the test if it does not tell me anything? Why are reputable companies like Quest and Labcorp, national testing giants, offering the test if it isn’t accurate?
The results are not clear or definitive
Most have language about how the results are not clear.
CityMD: “Serum Antibody IgG (Blood Test): Regardless of your results, you should continue to exercise universal precautions such as social distancing, quarantining, frequent hand washing, wearing of a mask or face cloth in public, and other CDC guideline recommendations. Remember, COVID-19 is a new infection, and it is unclear if a positive antibody definitively offers immunity.” CityMD uses the Abbott test. In New York City, testing is free.
Labcorp says: “Your test results may help identify if you were exposed to the virus that causes COVID-19 and, if so, whether or not your body has developed antibodies. Although having antibodies usually gives immunity from further infection, there is not enough evidence at this time to suggest that people who have antibodies against SARS-CoV-2, the virus that causes COVID-19, are protected against future infections from the virus. Results from this test also will not provide information on whether you can spread the virus to others and is not used as a basis for diagnosis.” It also notes that false positives are possible.
Why do so many people want tests if the results are not actionable?
People want certainty, especially here in New York in pandemic central. Also, the nationwide test shortage has meant that people want tests more than ever — a respiratory test or an antibody test.
My thoughts when I got a positive test included: “Yay, I’m home free! I will volunteer for all the trials I can volunteer for, and share my antibodies and genes with anybody!”
But I’m not immune. Also, there’s that one negative test …
According to human nature, we lust for the test — conveniently skipping by the fact that the test seems at this point to be 1) not reliable, whatever test it is, and 2) not proof of immunity.
So why get this test? Why not focus on the things we know are working: Stay home. Wear a mask. Wash hands. Be careful until you know things have changed.
Questions you might have
Should I get a test? Ask your doctor.
No really, should I? What are your reasons for wanting a test? If you want a certain answer about whether you had it or have it, you might not get that. If you’re asking to be given permission to leave self-isolation, do not use these tests for that purpose.
I hear there are two kinds of test — one for active infection and one for the presence of antibodies, which suggests immunities. Can you explain? The one for active infection is usually done with a swab stuck into your nose or elsewhere in the respiratory tract, and the resulting sample is tested at a lab. Another kind of testing is now being done, serological (blood) testing for the presence of antibodies to the virus.
My work needs me to have a test. What should I do? Ask them why — the truth is that these tests do have errors. Better ones may be on the way. In any case, most scientists will say you should not base your personal behavior on these tests. Also ask your employer what test they need — the one for active infection, or the one for antibodies. Also ask: Will you pay? How do you want me to show you the results? Can you give me written, detailed instructions? Many workplaces have a hard time understanding these subtleties.
I need to have a test to get my sick pay for the days off I took for what I believe to have been coronavirus. My employer requires this before I can get my pay. See above on employers.
I need to get tested to know if I can go see my elderly mom (immunocompromised brother) etc. What should I do? Again, these tests are not going to prove that you are immune or not able to give the virus to someone else. The tests are not that reliable. Remember, the virus can be passed on not just through breathing but also by taking virus particles from, say, a doorknob and delivering them with your mom’s groceries. Stay safe.
My son tested positive on the respiratory test this spring, but now he needs a negative test to volunteer. What should I do? I believe in this scenario, the volunteer organization is looking for a swab or nasal test to confirm that he has no active viruses in his system. Confirm with the volunteer organization, and ask them for detailed, specific instructions in writing. (The nasal test also has a lot of errors.)
My son tested positive this spring, and now he wants to give plasma. What should I do? I believe in this scenario, the organization is looking for presence of antibodies to confirm that he had exposure to the virus in the past. Confirm with the organization, and ask them for detailed, specific instructions. Also, here’s a list of plasma donation and other studies. If you sign up, they’ll get in touch if you fit their criteria.
My doctor said the test was approved by the FDA. Doesn’t that make his test the best? The FDA approval process has been sorely lacking. Read here. The underlying scientific data on test performance is here. But remember, these are self-reported to the FDA and there hasn’t been enough time to really confirm performance.
My doctor’s office is offering the test, so isn’t that safe? It depends on what you think of as safe. Again, the results are unreliable, and most doctors will tell you that you should not use the test results to make decisions about where to go and what to do.
My doctor’s offering the test, but his nurse said don’t get it. What should I do? Think carefully about what you expect to gain from a test. Remember, they’re not all that accurate, and results shouldn’t be used to govern personal behavior — a positive antibody test is not a free pass to leave isolation.
I never tested positive but I know I had it. Should I get tested? We’re not doctors. But since we know a little about the reliability of the tests, we suggest that you think carefully about why you want to get tested.
I want one of these “immunity passport” things I’m reading about, certifying that I had it and I’m now safe. What should I do? The “immunity passport” idea has been discarded. First, the tests aren’t that accurate, and second, even if they do confirm that you have antibodies, no one knows whether those antibodies will protect you from another infection.
Some tests are better than others, I hear. I want the best one. What is it? There are a lot of people out there selling tests that have not been authorized by the FDA. Scammers will find ways to scam people. What’s the best one? The science is still out on this one, but Michael Osterholm, a well-respected scientist who runs a center studying pandemics at the University of Minnesota, said he thinks the best one is being used by Mount Sinai Medical Center in New York City. It’s a two-step process, he said. The Mount Sinai test is not commercially available; scientists there are using that test to qualify potential donors for a convalescent plasma trial.
Wait, there’s an at-home test! Why shouldn’t I use that? At this point the FDA has not authorized any at-home tests. There are a lot of people trying to make money on coronavirus testing, so you should be cautious. For example, LetsGetChecked.com is promising an at-home test. They don’t have one now. They just raised a ton of money, $71 million to be exact. Would you choose them to test you? Why?
If it’s not about testing, what is it about? Scientists say testing is an important element of dealing with the pandemic. But other important elements should not be disregarded: Tracing the contacts of infected people, social distancing, hand-washing, mask-wearing, responsible conduct in general.
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