Meantime, at the Mayo Clinic in Rochester, Minnesota, researchers are preparing to start a clinical trial in which patients who test positive for COVID-19 would have their blood collected at the time of diagnosis, and again 15 to 20 days after that in the patient’s home.

The trial is designed to show when people who have COVID-19 infections “seroconvert” – when antibodies produced by the body begin to show up in blood tests. That information will be useful in determining the best time to conduct the tests.

“You don’t want to do it too soon because of the risk of false negatives,” said Elitza Theel, director of Mayo’s Infectious Diseases Serology Laboratory.

Mayo also is evaluating the performance of antibody tests from several companies, including two from China.

The U.S. Centers for Disease Control and Prevention said it is working on its own version of antibody tests, but it has not given a timetable. The agency has said extensive research is underway. One challenge for the CDC and other labs is to get enough blood samples from people who have already been infected to verify the antibody results.

The agency faced heavy criticism for sending a faulty diagnostic test to state and local labs early in the coronavirus epidemic and then taking weeks to fix it. The federal government is still trying to expand diagnostic testing capacity.

MONTHS OF IMMUNITY

The potential for antibody testing arises as U.S. President Donald Trump is considering scaling back “social distancing” and stay-at-home advisories in the weeks ahead. His political allies argue that the toll on the U.S. economy is too severe. About half of Americans have been ordered to shelter in place as many schools and businesses remain shuttered indefinitely.

On Tuesday, Trump said: “I would love to have the country opened up and just raring to go by Easter.”

Reopening offices and businesses without fear of triggering more infections, however, has been complicated by the lack of testing to diagnose COVID-19 cases across much of the country.

On Monday, Dr. Deborah Birx, a member of the White House coronavirus task force, said simple, finger-prick antibody tests could play an important role, and she suggested the federal government is not waiting on the CDC’s version.

“Some are developed now. We are looking at the ones in Singapore,” Birx said Monday at a White House press briefing. “We are very quality-oriented. We don’t want false positives.”