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Coronavirus Testing: How It Works and When to Get Tested

Rapid tests and antibody tests may be keys to resuming normalcy

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AP Photo/Gerald Herbert

It got off to a rocky start — and with ongoing supply shortages, it's still far from perfect. But testing for the new coronavirus is ramping up throughout the U.S., and it's expected to keep expanding.

Here's a look at what's currently available and what's on the horizon for coronavirus testing:

How many different coronavirus tests are out there?

Before the coronavirus started spreading in communities across the U.S., there was just one type of test to detect an infection. This test kit was made by the Centers for Disease Control and Prevention (CDC) and was distributed to a handful of state and local public health labs.

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But since the end of February, more than 25 types of coronavirus tests have come on the market. These have been developed by commercial manufacturers and granted emergency use authorization by the Food and Drug Administration (FDA) — a fast-track approval process of sorts that helps to push out potentially lifesaving tools during a public health emergency.

To date, nearly 1.8 million tests have been used to identify cases of coronavirus in the U.S., according to the COVID Tracking Project. COVID-19 is the disease caused by the new coronavirus.

How do the tests work?

The majority of the available coronavirus tests work similarly: They look for the virus’ genetic material in a sample of mucus, which is usually collected by a nasal or throat swab administered by a health care worker, says pathologist Timothy Stenzel, director of the Office of In Vitro Diagnostics and Radiological Health at the FDA.

One test that has received an emergency use authorization, however, is different: It's a blood test, for starters. And it can tell whether a person had the virus by identifying antibodies, which are basically a signal that the body already responded to an infection.

How long does it take to receive test results?

That depends on a few things. Most of the tests in use are analyzed at off-site laboratories, and results can take anywhere from a day to more than a week to get back to the patient. The major reason for testing delays now is not a lack of testing kits, as was the case at the start of the outbreak. Now the holdup is shortages of the “ingredients” needed to process the tests in the lab, says Eric Blank, chief program officer at the Association of Public Health Laboratories.

"I think the public perception is the swab goes into a black box and then a result pops up. And there's a lot more to it than that,” Blank says.

Reagents, swabs and transport mediums needed for the multistep process are in high demand around the world as the coronavirus continues its spread. “So it's not just a U.S. problem; it's a problem globally. It is getting better, but it's still going to take a while before the pipeline gets filled and we're getting all the supplies we need,” Blank says.

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What about rapid coronavirus tests?

Some tests that have received approval are called rapid tests. With these, the results come back much quicker — we're talking minutes. These tests are being used at hospitals and emergency rooms to help health care professionals triage patients in need of urgent care.

Knowing right away whether a sick patient has the virus can help inform health care staff if a patient needs to be isolated from others in a busy waiting room, for example. A diagnosis can also help doctors and nurses with limited supplies of personal protective equipment know when they need to wear it and when they can save it.

Can we expect to see more of these rapid tests?

That's the hope, Stenzel says. When more of them are available, public health experts envision these rapid tests as a tool that can be used outside of critical care settings. They could help determine when someone is ready to go back to work, for example.

"As long as they're negative, they don't test positive for the virus anymore, they may be safe [to return to work]. And I emphasize 'may' because we're still learning a lot about this virus,” Stenzel says.

What is this coronavirus antibody test?

Unlike other tests on the market, the antibody test (also called a serology test) does not diagnose a current infection. “It signifies that the person has been exposed to the virus long enough that their immune system has been responding to it,” Stenzel says.

It's important to remember: Many people who are infected with the coronavirus do not experience symptoms. And knowing whether someone has been infected but wasn't sick can also pinpoint people who may be in the clear to return to normalcy.

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People who have already had the virus are “probably not going to be a danger to other people,” Stenzel explains. Scientists are still working to better understand if and how the virus mutates, but Stenzel says the thought is that those who have “been exposed to coronavirus and have developed immunity and have completely recovered, hopefully won't get it again.”

Public health experts are also looking to serology tests to paint a more complete picture of how the virus spreads and to better understand its fatality ratio. The CDC is developing its own serology test for this reason.

What other tests can we expect to see? At-home tests?

In addition to rapid testing and tests that identify past infections, some experts believe at-home testing is part of the future.

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Pathologist Michael Mina, assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health, says he wouldn't be surprised if coronavirus tests are eventually “sold at CVS and things like that … potentially to the tune of somebody being able to order a pack of 10 and use one every week.”

How would these be useful? They could help “the everyday individual know their status and be able to have some idea” of whether they have the virus or may be immune to it, Mina says. Again: It gives people a better idea of when they can return to normal life. It could also help indicate when nationwide social distancing practices can be relaxed.

"If we knew what the test results were for each person, we would be having them individually social distance, which would be better,” Mina says. “But at the moment, we're kind of stuck in this rut” of everyone social distancing, which is “highly detrimental to the economy and to our lifestyles, and pulls at the social fabric of society, frankly.”

How accurate are these tests?

Some experts question the sensitivity of the new coronavirus tests because of how quickly they are being funneled through the FDA's emergency approval process.

"Obviously we've been wanting more testing,” says William Hanage, associate professor of epidemiology at the Harvard T.H. Chan School of Public Health. And while “the availability of new kits is welcome,” he says the influx “produces a problem of its own.” Because the tests are made by different manufacturers, they vary slightly, and “the lack of consistency” could “create noise in the data,” Hanage adds. “And we're going to have to figure out how to deal with that.”

As Blank explains: “You can't afford a false negative. Because essentially, you said to a person, ‘Oh, you don't have it,’ when, in fact, they might very well have it. And we can't really afford a false positive because now you're using resources that are in short supply within the health care system broadly on somebody.”

Under normal circumstances, FDA approval for tests takes around 90 days, Stenzel says; with a public health emergency, the process is much faster. Stenzel says that once the FDA approves a test, the agency continues to monitor its performance. Manufacturers also are required to report problems back to the FDA.

How do I know if I need a coronavirus test?

Mass testing is a goal of the future, but right now not everyone needs to be tested, according to the CDC — even those who think they may have COVID-19.

For starters, there is no specific treatment. And people with mild cases of the disease can often recover at home. If you are showing symptoms of COVID-19, including fever, cough and shortness of breath, call your health care provider. Your doctor can let you know whether you need a test and where you can get it.

What will it cost me?

New legislation, signed into law March 18, makes coronavirus tests available at no cost. But it's always a good idea to check with your insurer and health care provider about any out-of-pocket expenses for the test and the doctor's appointment (or telehealth appointment) to determine if you need one.

What happens if I test positive?

Most people who are diagnosed with COVID-19 are able to recover at home. The CDC has specific guidelines on what home recovery looks like and what you should — and shouldn't — do if you're sick from the coronavirus.

The key is to keep your doctor up to date on symptoms, especially if they worsen. People with more severe illness may need medical attention. If you develop emergency warning signs for COVID-19 — trouble breathing, persistent pain or pressure in the chest, new confusion or bluish lips or face — get help immediately.

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