Quest Diagnostics is letting people sign up for antibody tests for the novel coronavirus online.

Starting Tuesday, people in the US can order the tests on Quest's website without visiting a doctor.

At $119, the kit is one of the more expensive items offered on Quest's site. It requires a blood draw at one of Quest's 2,200 locations.

While there's still much to be discovered about immunity to the coronavirus, antibodies for respiratory illnesses typically confer some level of protection against future infection.

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Quest Diagnostics is rolling out antibody tests for the novel coronavirus that you can buy online.

Starting Tuesday, people in the US can order the tests on Quest's website without visiting a doctor's office. The test costs $119, and requests are reviewed by licensed physicians. After ordering the test, you have to go to a Quest testing center to give a blood sample.

The tests aren't used to diagnose a current COVID-19 infection — rather, they're intended to figure out whether people have already had the disease.

The test looks for antibodies for the coronavirus in your blood. Your body makes antibodies to fight off infections, and they typically last for a while after you're exposed to a virus.

While there's still much to be discovered about immunity to the coronavirus, antibodies for respiratory illnesses typically confer some level of protection against future infection.

Quest's test is the first that people can order themselves, despite the steady flow of antibody testing kits into the US healthcare system. Quest's tests are supplied through Abbott Labs and PerkinElmer's Euroimmun business, and the lab giant has said it expects to run 150,000 tests a day by early next month.

How it works

Once a person's test request is approved, they'll need to visit one of Quest's 2,2000 laboratories and have their blood drawn by a technician. Results should be available within two days on the MyQuest patient portal, according to the company.

At $119, the kit is one of the more expensive items offered on Quest's site and is not covered through insurance. To be eligible, people must not have experienced COVID-19 symptoms for at least 10 days. They also have to wear face masks in the lab and have their temperature checked when they arrive.

Customers will have the opportunity to speak to a physician about their results, Quest said.

Quest's website doesn't say how accurate the tests are, though the company did identify situations that could lead to incorrect positive or negative results.

Abbott has said its antibody kits are 100% accurate in detecting coronavirus antibodies, a metric called "sensitivity." Euroimmun did not disclose the kits' sensitivity on its website but said they're highly accurate.

Inaccurate tests loom

Concerns have mounted in recent weeks as more than 140 sellers have flooded the market with unapproved antibody kits.

The US Food and Drug Administration lowered the bar for approval in an effort to make the tests more widely available during the pandemic. Some of the companies, however, have provided misleading information about FDA authorization, withheld information about accuracy, or vetted the tests for different purposes than what they'll actually be used for, according to the agency and reporting by Business Insider.

A study backed by Mark Zuckerberg and Priscilla Chan last week published preliminary data about the performance of several popular antibody testing kits. It found that the tests were 81.82 % to 100% sensitive after 20 days since the onset of symptoms but performed worse with less time since the onset.

The study began before several major healthcare companies announced the availability of antibody tests. Abbott, Siemens Healthineers, and Roche all make the tests, and Beckman Coulter plans to as well. Together, the companies plan to make tens of millions of tests each month by the summer.

Consumer-ordered tests in short supply

Despite dozens of companies' interest in antibody, or "serology," testing, consumer-ordered tests have been in short supply. That's largely because of the FDA's stricter standards for self-administered kits.

"With the introduction of this test and service, Quest is making it easy for people to access quality testing for antibodies to the virus which causes COVID-19, with access to physician interpretation and steering into needed care," Jay Wohlgemuth, Quest's chief medical officer, said in a statement.

"Our goal is to empower individuals and their physicians to make informed decisions about their risk of infection and of spreading the virus," he said.