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Will serological tests save us?
Researchers have begun testing people for antibodies to the coronavirus. But do we know enough about immunity to make this a big part of our response?
Welcome to Not a Doctor, the only newsletter about health and science that adds massive (and hopefully figurative) grains of salt to your diet.
I’m Melody Schreiber, a journalist and the editor of What We Didn’t Expect. I’m not a doctor, or a scientist, or really an expert of any kind. I just like to ask questions and try to find the answers to them.
Today I want to talk about serological tests. What are they, what do they do, and how are we using them?
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What are serological tests?
Serological tests are blood tests — either from a blood draw or a simple finger-prick — that test your blood for antibodies to an illness.
It sometimes takes days or even weeks for your body to get those virus-fighting immunoglobulins to swing into action, though, so often you can’t get the test until two weeks or so after you were infected.
This is different from an actual coronavirus test, where swabs from your nose or throat are examined to find active virus particles. These tests can be used to diagnose a current COVID-19 infection.
Serological tests, on the other hand, cannot technically diagnose COVID. Instead of finding the virus particles themselves, they look for the antibodies.
And that’s where this simple test gets really complicated.
Photo: Neuroscience News
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It’s not clear how well these tests work
There are a few problems with serological tests for the coronavirus.
First, we’re not sure how accurate most of the serological tests are. Only four tests have received emergency authorization from the FDA, while many others have been developed under guidance the FDA issued to help speed along the process without authorization.
That means each test-maker is basically going on their word that their test works.
When these tests don’t work, it’s often because it was really, really hard to find blood samples taken from a patient who had a confirmed COVID-19 infection in order to make sure the test is accurate. Hospitals are, quite understandably, very busy right now; if they’re able to draw the blood at all, they may not have time to share it with researchers and companies.
It’s also possible that the tests are actually confirming the presence of *a* coronavirus, but not *the* coronavirus. There are milder coronaviruses that have circulated for years, usually showing up as the sniffles or a light cold. It’s possible some serology tests are finding antibodies to these viruses instead of to SARS-CoV-2, the more serious virus that causes COVID-19.
And then there are the unscrupulous companies peddling tests that probably never worked, just to make a quick buck off of our desperation to know whether we and our loved ones have been exposed.
One of the reasons this is dangerous has to do with false negatives and false positives.
If you take the test and it says you’re negative, then you might breathe a sigh of relief and not take extra-strict precautions to protect others. But the test could be malfunctioning, or it’s very possible not enough time has passed for your body to create antibodies yet.
If you take the test and it says you’re positive, you might breathe a different sigh of relief. Great, you already had COVID-19, and now you’re immune, right? Right?! We’ll talk about immunity next, but if the test malfunctions and says that you have antibodies when you don’t, you might think you’re safe from the virus when you’re actually not.
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We know very little about immunity with this coronavirus
Based upon how other coronaviruses and respiratory viruses work, researchers think you’ll have immunity for a few months or even a few years after you have the virus.
But SARS-CoV-2 is a brand-new virus, and there’s a lot we don’t know about it. What if it functions differently than other coronaviruses when it comes to immunity? What if we actually don’t know that much about immunity to respiratory viruses, because we haven’t had a pandemic in so long and health research is chronically underfunded?
I wrote about this and other aspects of serological tests for The New Republic recently — including some preliminary research that indicates some patients may not develop antibodies at all.
Since I wrote that piece, officials from the WHO also said that the presence of antibodies doesn’t mean you’re immune.
“These antibody tests will be able to measure that level of serology presence, that level of antibodies, but that does not mean that somebody with antibodies” is immune, said Dr. Maria Van Kerkhove.
More preliminary serological surveys have been conducted in places like California and Boston — but the results have been controversial.
One preprint study — meaning it has not been peer-reviewed or published in a respected journal, so huge grain of salt here — was conducted by Stanford University in Santa Clara county. The researchers estimated that 2.5 to 4.2% of residents were infected with the virus.
However, experts have questioned these methods and results. For instance, the researchers assumed their tests were about 98% accurate. But given the issues I mentioned above with test accuracy, that seems like a huge assumption. If the tests are only 95% accurate, that would dramatically change the estimates of who would test positive.
The second preliminary study wasn’t even a preprint, from what I can tell. This report by the Los Angeles Times seems to have been based on a press release or press briefing. Because there is no data for epidemiologists to comb through, I don’t even want to discuss those potential findings here.
I mention this research, however, to illustrate a point: Research is ongoing, and you’re going to see a lot of reports of varying quality about how many people have had the virus based upon serological studies. Until these studies are examined closely, though, they need to be approached with caution and care.
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Learning more about immunity
Researchers told me that we simply don’t know enough about immunity to make serological tests a core part of our response to the virus.
The best solution is to keep doing more of what we have been doing. Making more tests for the active coronavirus particles, making more personal protective equipment, paying health workers fairly for the risks they undertake, staying home whenever possible.
Source: Bill Hanage
However, these tests are still useful in the way they’ve traditionally been used. Results from serological surveys could go a long way in helping us figure out what kind of immunity an infection does give us, and how long it lasts; and the tests can help us figure out where and how the virus has spread.
These tests won’t get us out of this mess, but they will make significant contributions to our knowledge of the virus.
That’s still really important to keep in mind. There are no magical shortcuts to fixing this pandemic. Instead, it’s about using all of the tools we have, in a responsible way.
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