The laboratory processing most of Washington state’s COVID-19 tests will soon begin doing another kind of test, to identify people who have recovered from the disease and have developed antibodies to the virus.

“We’ve heard these stories,” said Dr. Keith Jerome, head of the virology division within the UW Medicine’s department of laboratory medicine. “Somebody says, ‘I was really sick in February. Did I have COVID?’ And we haven’t been able to tell them.”

The UW Medicine Virology Lab plans to begin answering this question next week by testing blood samples from people who have recovered from COVID-19.

Serological testing — checking for antibodies — is important because it identifies who has had the disease and helps to build a picture of how widespread the virus is, which can inform decisions about lifting distancing orders and allowing businesses to open.

“This starts to get us to a point where we can start to make a difference in the population of our area and get people back to work and give them back the lives they were hoping for,” Jerome said at a news conference Friday to discuss the antibody testing.

At first, the lab will be able to process 3,000 to 4,000 tests a day. That number will increase to 12,000 to 14,000 tests per day once more equipment is moved to the lab from Harborview Medical Center, although it’s unclear when that will be.

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Any health-care provider who thinks their patient should be tested for antibodies will be able to send in a sample of the patient’s blood, Jerome said. It would make sense for health-care workers, first responders and anyone working near other people to have blood samples submitted, he said.

The test isn’t for people who currently have COVID-19 because it can take five to 14 days after symptoms appear for antibodies to develop, Jerome said.

An advantage of moving quickly on antibody testing is that the virus is new and present so the antibodies flowing through people will be strong, said Dr. Alex Greninger, the lab’s assistant director, who joined Jerome at the Friday news conference.

Several other Seattle-area labs have also started testing blood for antibodies to the novel coronavirus or are developing new approaches to testing.

One of the major unknowns about the epidemic is its impact on children, who do not seem to get as sick as adults, said Jesse Bloom, a biochemist at the Fred Hutchinson Cancer Research Center. He has been working with Dr. Janet Englund, at Seattle Children’s hospital, to test kids’ blood and estimate what proportion might have been infected. They expect to release their results soon, he said Friday.

In addition, Bloom is using a more sophisticated type of test than the one at UW to better understand immune response to the virus. In particular, he is measuring how well the antibodies work to actually neutralize the virus — a key indicator of the level of immunity conferred by infection.

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Other local researchers are using those more sophisticated tests to screen plasma donated by people who have recovered from COVID-19. The plasma is being used to treat critically ill patients, but screening might be able to identify donors with the most potent plasma and boost the treatment’s effectiveness.

Larry Corey, a virologist and former director of the Hutch, is working on an alternative approach to testing that might be quicker and more effective.

After the first wave of the epidemic passes, Corey said, the only way to find out what percentage of the populace has been infected is through a blood test to detect antibodies to the virus.

“Where this will plateau, I don’t know,” Corey said. “What’s going to be the basal level of activity of COVID-19? For that, we need a serological tool.”

If only a small fraction have been infected, that means the majority remains susceptible to the virus and a relapse outbreak is possible.

Corey and several of his colleagues at the Hutch are also working on new blood tests, which they hope will be ready within the next couple of weeks.

Greninger and Jerome are pleased with early results from the antibody tests performed at UW Medicine’s Virology Lab. They were able to test samples the lab already had on hand, including 300 samples taken last fall, before the virus began infecting humans. None of those tests turned up positive results.

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“We not seeing any false positives with this test,” Jerome said.

Robust antibody testing will help researchers figure out how long and how well antibodies protect against the virus. Antibodies from other coronaviruses can last a year or two, sometimes three, Jerome said.

“To what degree that protection happens is something that the entire medical field is trying to figure out now,” Jerome said. “We can find the virus, and we can also find who had it and find these antibodies.”

Testing for the novel coronavirus has been hard to come by for some Washingtonians, in part because of a limited availability of testing materials. Those supply challenges shouldn’t arise for the antibody test because it is a blood draw and the test is built on the same platform that’s already used for AIDS and hepatitis C, Greninger said.

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