Coronavirus testing explained

As the White House and state governments debate the best way to reopen the economy and relax social distancing guidelines, the need for more coronavirus testing keeps coming up.

“It can be extraordinarily helpful in terms of guiding our framework and indicators for reopening,” California Gov. Gavin Newsom said this week about expanding his state’s testing capacity. “It’s not, at this moment, a panacea, but it could be profoundly significant.”

Commercial labs and health departments test about 150,000 Americans a day, according to the COVID Tracking Project. Some experts believe that number needs to be in the millions to safely reopen the economy. Broadening testing for patients with active COVID-19 would allow officials to quickly isolate new cases and keep the disease from resurging. And testing for antibodies to the virus would allow those who might be immune to get back to work.

But across the country, the availability and reliability of tests have lagged. Initially, the Centers for Disease Control and Prevention issued faulty test kits, and labs struggled with shortages of swabs, reagents, and workers. Additionally, the CDC’s single testing center could not run enough samples for a country with 329 million people.

The CDC eventually allowed state labs to run the tests themselves, but the backlog remained a problem, David Pride, associate director of microbiology at the University of California San Diego, wrote for The Conversation.

Now, private companies, hospitals, and academic centers are trying to develop their own tests. But most labs were unprepared to speed up a process that typically takes months.

“We could only obtain materials … from the CDC or private industry, who were all being bombarded with our requests simultaneously,” Pride wrote. “We laboratory directors were suddenly competing with one another for limited resources to develop these tests.”

Most tests to identify those who have COVID-19 involve polymerase chain reaction testing, known as PCR. Workers swab the nose and throat and then send the samples to a lab to check for the virus’ RNA. PCR tests take only a few hours, but preparing samples and sending them to central labs takes time. Some people have waited a week or more for results from overwhelmed labs.

Some companies are developing tests that healthcare workers can perform quickly in a doctor’s office or drive-thru site. At the end of March, Abbott, a medical technology company based in Illinois, announced it would roll out a test that can detect COVID-19 in five minutes and identify negative results in 13 minutes. The company immediately ramped up production and placed 18,000 testing machines in doctors’ offices, clinics, and hospitals across the country. Though it now delivers 50,000 tests per day, many of the sites did not use the tests at first due to staffing and supply shortages. Then a study at the Cleveland Clinic in Ohio found that Abbott’s test produced false negatives in 15 percent of 239 cases. False negatives can undermine a clinic’s safety measures.

“If you have patients coming into the hospital and you’re going to put them into what has been determined to be a COVID-free ward, you have to have the most sensitive test available,” Dr. Gary Procop, who headed the study and leads testing at the Cleveland Clinic, told NPR. “Because once you put somebody with COVID into a COVID-free ward, it’s no longer COVID-free any more. It’s your new COVID ward.”

Abbott issued a statement saying improper storage of samples likely produced the high percentage of false negatives.

Even if accurate, point-of-care tests in clinics can only test one person a time, David Kroll, a professor of pharmacology at the University of Colorado, told Live Science. Clinics can’t run the large number of tests necessary to give experts a clear picture of the pandemic’s spread.

Other researchers are working on a way to pool several tests and run them together, according to MIT Technology Review. If the pooled sample tests negative, everyone in the group is clear. If it tests positive, the members can undergo individual testing. In theory, the process could test 100,000 samples at once for about $7 each. Other researchers are working on tests people can do at home and mail in.

Research suggests many people likely had the virus but never developed symptoms. Serological blood tests aim to detect antibodies and identify those people, who likely have at least temporary immunity. The immune system produces antibodies days or weeks after an infection to destroy the disease, and they can stay in the body for anywhere from weeks to years. Serological testing could allow those with some immunity to safely return to work.

But some experts are concerned that there hasn’t been enough time to thoroughly analyze these tests. The U.S. Food and Drug Administration granted emergency authorizations to speed up the process, so the sensitivity level of the tests is unclear. If they are too sensitive, they will return false positives on people who aren’t really immune. On the other hand, if the tests are not sensitive enough, they won’t get people back to work any sooner.