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Coronavirus Testing: What To Know About Antibody Tests, Antigens And Serology

Tests that detect whether you’ve had COVID-19 and recovered could help us navigate the pandemic. Here’s what you need to know.

In the ongoing battle against the coronavirus pandemic, antibody testing is being touted as a key step that could herald the end of social distancing and the reopening of the economy while we wait for a vaccine. Other phrases being bandied about include “antigen testing” and “serology,” each holding some promise of a return to normalcy. When you add blood tests, nose swab testsdrive-through testing sites and at-home test kits to the conversation, it can be hard to tease out which tests do what and what the results even mean.

Antibody tests have been in the spotlight recently because they may be able to tell if you’ve ever had COVID-19, even if you never showed any symptoms or even knew you had the disease. If you did, it could mean you’re immune to the coronavirus and are safe to be around others.

But there’s a lot of confusion and debate about what antibody tests can and can’t do, if they’re even reliable enough to tell us anything useful, and where and how you can take the test when it becomes available. Here’s what we know (and don’t know) so far.

One more note: This article is intended to be a resource to help you understand current coronavirus testing as presented by organizations such as the US Food and Drug Administration and Centers for Disease Control and Prevention. It isn’t intended to serve as medical advice. If you’re seeking more information about coronavirus testing, here’s how to find a testing site near you (here’s another way for Apple Maps users). Here’s how to know if you qualify for a test and why there aren’t any coronavirus at-home test kits yet. This story is updated frequently as new information comes to light.

What is antibody testing for coronavirus?

An antibody test is a type of medical test that could help doctors determine if you have ever been infected with the coronavirus, regardless of whether or not you ever felt sick. This is important because many who contract the disease are asymptomatic.

Antibody testing does not, however, reveal whether you are currently infected with the virus, nor does it indicate whether you have recovered from it if you did have it. The test only shows whether or not at some point you had the virus — nothing more, nothing less.

Why is the antibody test such a big deal?

A positive antibody test result usually means you’re immune to the disease being tested for. Although researchers don’t know enough about COVID-19 yet to be able to say for sure whether you’ll be immune, the hope is that people who have recovered from the disease won’t be able to catch it again, or, for that matter, infect others.

If that turns out to be the case, once a high enough percentage of the population has developed immunity to the coronavirus, a form of indirect protection called “herd immunity” might shield those who haven’t been exposed yet from getting the disease — and help usher in an end to the pandemic.

Can antibody tests tell if you’re immune to coronavirus?

With other diseases caused by coronaviruses — like SARS and MERS — a positive antibody test usually indicates some degree of immunity. However, the World Health Organization has warned that scientists don’t know enough yet about this new coronavirus — which is technically called SARS-CoV-2 — to be able to say one way or the other. They’re working on figuring it out.

How does antibody testing work?

Antibody testing looks for proteins in the blood, called antibodies, which are left over after your body fights off a disease. When your immune system detects a new infection, your body starts producing antibodies, which it then trains to fight that specific invader. These antibodies figure out the invader’s weaknesses, then neutralize, destroy and ultimately remove it from your body.

After it’s gone, your body continues producing antibodies in case it ever comes back. That’s what the coronavirus antibody tests look for — the leftover antibodies your immune system produced to fight the coronavirus.

Where can I get a coronavirus antibody test? 

For now, you’ll have to start by talking to your doctor or another health care practitioner who is licensed to order lab tests. Guidelines vary by provider and by state, but generally you have to have been asymptomatic for one to two weeks (including the day of the test).

Up until this week, antibody tests have not been widely available in the US, so health care professionals and first responders have been given priority. But starting April 27, you can get an FDA-authorized coronavirus antibody test at LabCorp facilities or doctors’ offices and health care facilities staffed with a LabCorp technician (there are thousands nationwide).

Right now, only the LabCorp test and three other antibody test kits have been authorized by the FDA under a rule that allows medical devices to be used during a public health emergency prior to FDA review. Under a similar emergency policy, the FDA is also allowing the use of test kits from nearly 100 other manufacturers, but some experts warn you shouldn’t trust such tests until they have been vetted more thoroughly.

What is an antigen?

An antigen is a substance that usually comes from your environment and makes you sick when it gets inside your body. Common antigens include bacteria and viruses. Antigens trigger your immune system to produce antibodies, which fight back.

Antigens can get into your system much the same way you bring the substances you need to survive into your body. You can inhale airborne antigens into your lungs when you breathe, for example. Or you can bring antigens into your mouth when you, say, pick up an infectious substance like the coronavirus off a surface with your hands, then touch your face.

Antigens can also get into your body through your ears, eyes and nose. Rarely, but occasionally, you can absorb them through your skin.

How is antigen testing different from antibody testing?

An antigen test looks to see if you currently have the disease by searching for genetic information unique to a particular virus or bacterium. It tells doctors whether you are currently infected or not, but not if you were infected in the past and have since recovered.

Conversely, an antibody test only shows whether or not you’ve had the disease in the past. It can take up to two weeks for antibodies to be detectable in your blood — usually long after the virus has been defeated and an antigen test would come back negative.

What is serology or a serology test?

Serology refers to the study of blood serum, and the vast majority of serology testing is done to detect antibodies. Other body fluids, like saliva, can be tested too, but that’s because they contain trace elements of blood, which is what’s actually being tested.

Serology tests can also determine blood type when donating blood or receiving a transfusion. They can be used to measure the levels of pharmaceuticals present in the bloodstream, during a drug trial, for example. But most of the time, when experts use the phrase “serology” or “serology testing,” they’re talking about antibody tests.

Although increased antibody testing may help hasten the end of lockdown, it’s not the only thing that can speed the return to normalcy. Here’s a look at what needs to happen before shelter-in-place orders begin to be lifted in the US. If you or someone in your home contracts COVID-19, here are the steps you need to take to avoid spreading the virus further. And here’s what to do to stay safe when you have no choice but to venture out in public.


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