From an arm to a lab, how novel coronavirus antibody testing works

A small needle is inserted into a vein of an arm and soon, blood is seen flowing through a tube into a vial for a novel coronavirus antibody test.

The vial, filled with blood, is put into a centrifuge after the blood clots and spun for about 10 to 15 minutes, with the serum from the blood cells emerging on top and the platelets underneath.

Once the serum and the platelets are fully separated, the vial is ready to be sent to the lab for testing.

"For this particular antibody test, they need the serum portion of your blood and so that's why we pop it into the centrifuge," Bianca Torres told Reuters in New York on Thursday (May 7). Torres is a phlebotomist at membership-based primary care practice One Medical.

Unlike tests to diagnose diseases, antibody tests show who has been infected and recovered. The body makes antibodies in response to many illnesses and infections, including other coronaviruses. New blood tests are being developed to identify antibodies unique to SARS-CoV-2, the official name of the new coronavirus.

The tests look for two kinds of antibodies: immunoglobulin M (IgM) and G (IgG). The body quickly produces IgM antibodies for its initial attack against infections. It makes IgG antibodies more slowly and retains them longer; IgG antibodies suggest possible immunity.

One Medical's chief medical officer, Dr. Andrew Diamond, said that depending on their patients' insurance, their serology tests, through their lab partner LabCorp, are manufactured by Abbott and have an "extremely high-performing, 99.9% specific, 100% sensitive test."

Abbott Laboratories' antibody test for the new coronavirus is highly likely to correctly determine whether people have ever been infected with the fast-spreading virus, the company said, citing a U.S. study. Researchers at the University of Washington School of Medicine report in the Journal of Clinical Microbiology that Abbott's test had a specificity of 99.9% and a sensitivity of 100%, suggesting very few false positives and no false negatives.

Antibody tests can tell whether a person has ever been infected and are considered crucial in efforts to get Americans back to work safely as the presence of antibodies to the virus indicates possible immunity to future infection.

Abbott's test was launched last month under the U.S. Food and Drug Administration's relaxed rules for some coronavirus tests, allowing their distribution before regulatory clearance. It has since received emergency use authorization from the FDA. Abbott has already shipped more than 10 million antibody tests to hospitals and labs.

Roche Holding AG has said its antibody test has a specificity rate of more than 99.8% and sensitivity rate of 100%, and expects to ramp-up production to make more than 100 million tests a month by the end of the year. Roche's test has also received emergency use authorization from the FDA.

"That's going to minimize my number of false negatives," said WebMD Chief Medical Officer Dr. John Whyte, referencing the Roche antibody test. "That's what I'm concerned about as well as false positives."

And the antibody test would not be considered accurate enough even if the test was at 95% sensitivity and 95% specificity, according to Whyte.

"That sounds pretty good, but it's not when you're testing hundreds of thousands of people or millions of people," he said. "You could have tens of thousands of inaccurate information on both ways. So you want something that's greater than 99% in both of those measures."

Whyte said based on previous viruses similar to that of the novel coronavirus, like "SARS and MERS, presence of antibodies typically gave persons two to three years of protection. So that's a good sign. In other instances like this, antibodies usually give protection. For how long? We're not sure. But if I had to guess, I'm going to guess that the presence of antibodies gives some protection, if it's an accurate test."

(Production by Roselle Chen)

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