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Skeptics point out rapid tests aren’t totally reliable.
This story was originally posted by Stateline, an initiative of the Pew Charitable Trusts.
Epidemiologists and other public health experts are debating whether to use rapid COVID-19 tests as admission tickets to schools, businesses and entertainment and sports venues.
Even with the quickening pace of vaccinations, it will be months before all Americans who want COVID-19 vaccines receive them. As a result, testing could become ubiquitous as a requirement for students, office workers, spectators and visitors seeking to gather indoors.
Many enterprises have been doing such testing for months, from colleges and universities to Hollywood movie productions to professional sports teams. In New York, Democratic Gov. Andrew Cuomo has said he wants to use extensive testing to enable Broadway to reopen.
More venues will take up testing as K-12 schools expand in-person instruction and a wide array of businesses and entertainment venues welcome people inside.
Manufacturers of tests say they are seeing a surge in interest from both public and private sources.
But some epidemiologists think that with uneven test and lab quality and varying skill levels among people administering the tests, the effort isn’t worth the time and money.
“With that kind of testing in most situations, the juice isn’t worth the squeeze,” said Dr. Daniel Morgan, an infectious disease doctor and professor of epidemiology at the University of Maryland.
But others hold the opposite view. “Active disease testing is the missing link for schools and employers to give them full confidence to come back in person,” said Mara Aspinall, a professor of health diagnostics at Arizona State University who advises the Rockefeller Foundation on COVID-19 research.
The testing debate coincides with arguments over whether proof of a COVID-19 vaccine should determine access to public spaces.
The skeptics’ chief complaint is the tests’ uncertain reliability. “We don’t have a gold standard,” said Dr. Anthony Harris, who is also a University of Maryland infectious disease doctor and epidemiologist. “There is not one test that is perfect.”
The U.S. Food and Drug Administration approved all COVID-19 tests and vaccines on the market under an emergency use authorization. During a public health emergency, the FDA can waive or loosen certain evaluation requirements to get essential products to the public as quickly as possible.
Harris said that because of time constraints, the COVID-19 tests now on the market were mostly studied for their effectiveness on those exhibiting symptoms of the disease. “They are not necessarily evaluated on asymptomatic people,” Harris said, who would likely be the majority of the people being to screened to determine if they can safely enter a venue.
There are two general categories of diagnostic COVID-19 tests. Molecular tests, usually referred to as PCR (for polymerase chain reaction) tests, can detect the genetic material of the virus. Antigen tests detect protein fragments specific to the virus that causes COVID-19.
The PCR tests are considered far more reliable, but are pricey and take hours to produce results. The Testing Wisely website, led by Morgan, lists PCR tests as producing 10% false negatives compared with 37% for antigen tests. (A false negative result occurs when a test shows someone is negative for the infection when it is actually present.)
“I’ve been involved with [antigen] tests that have up to 40% false positives and negatives,” said Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy.
As an example of the tests’ unreliability, skeptics point to the failures of antigen rapid testing during the Trump administration, including at the White House reception honoring Supreme Court nominee Amy Coney Barrett.
At least 12 people who attended that September event later tested positive for COVID-19, including President Donald Trump himself, even though they had received negative rapid tests before being allowed in. More than 35 White House staffers and other Trump associates came down with the virus despite the ongoing testing there.
However, antigen tests are cheaper and return results faster—in as little as 15 minutes. These features make them attractive for on-site screening at, for instance, live events and airport terminals. A negative result would allow admission.
Harvard epidemiologist Dr. Michael Mina, one of the most prominent proponents of screening tests, has noted that while antigen tests can miss the presence of the virus, they are better at flagging people with moderate or high viral loads. That means they can identify the people most likely to infect others.
PCR tests have their own problems. While more reliable than antigen tests, they can show someone is positive for the virus up to 100 days after they are no longer infectious—an unnecessary overcorrection for admissions tickets.
The FDA has also recently approved rapid PCR tests that can produce results in just under an hour. In the NCAA basketball tournaments, the NCAA used PCR tests for men’s teams and antigen tests for the women, which caused an uproar over the unequal treatment.
But many epidemiologists stressed that the quality of FDA-approved tests varies considerably. Furthermore, the samples collected may be faulty or contaminated, the person conducting the tests might be sloppy and the labs themselves might be deficient. “There are crappy companies running good tests,” Harris said.
The problem of false positive and false negative results goes beyond the risk of exposing people to infection. Epidemiologists fear that excess faulty results could cause people to ignore results altogether and fail to take necessary public health precautions.
“People who want to do something or need to do something, like those who have to go to work—they probably wouldn’t look for a reason not to go to work if they didn’t feel sick,” said Maryland’s Morgan. “So, if they get a positive result, they may not choose to stay at home, figuring the test was wrong anyway.”
Osterholm said there should be national testing standards that explain who should be screened and how often, the meaning of positive tests and what actions those results should prompt.
But even epidemiologists skeptical about mass testing think it could occasionally be useful.
“If in a community prevalence is high and very few people have been vaccinated, then yes, I would say regular testing in schools and colleges and businesses can make sense,” said Harris.
“But if prevalence is low and you have a high vaccination rate, that reduces the value of testing and increases the probability that you are getting a lot of false positives.” It would be better to spend the effort and resources on other mitigation efforts and on getting people vaccinated, he said.
Dr. Michael Saag, a professor of infectious diseases at the University of Alabama at Birmingham who also advises the university on COVID-19 public health measures, said that while the school has run a robust testing program, it will soon scale it back. With a positivity rate of less than 0.1%, he said it’s just not worth it.
“I’m not trying to rain on the parade of testing, but there are things we can do in a common sense realm that are more effective than testing,” he said, such as masking and social distancing.
Testing in Schools
Testing remains central to reopening plans despite its shortcomings. The COVID-19 relief bill President Joe Biden signed last month provides nearly $50 billion for testing, including $10 billion for testing in K-12 schools to enable them to open their doors to even more students for in-person teaching this spring.
Many school systems have implemented multistage testing protocols. Some seem designed to address the reservations some epidemiologists expressed.
Baltimore is one of those school districts. In March, the city began reopening lower grades in the public schools for in-person instruction, with plans to open other grades this month.
To reopen safely, the schools have implemented a multilayered PCR testing procedure that begins with pool testing. In pool testing a group of people is tested to determine whether anyone in the group is infected, without disclosing who in the group carries the virus.
All students, teachers and staff in Baltimore are subjected to pooled testing once a week. The average size of the pools in the city schools is just under 13 individuals, said Cleo Hirsch, director of priority initiatives for the Baltimore city schools and the lead for its testing program.
The tests are self-administered and supervised, Hirsch said. Kids and adults swab the lower part of their nasal cavity and then drop the swab into a tube, which is then sent to a lab.
Hirsch said even young kids can perform the procedure. “It’s really easy, they say it’s like picking your nose,” Hirsch said. “Sometimes they giggle, no one cries.”
Results are returned in a day, Hirsch said. If they show that somebody in the group is positive, everyone in the group is given an individual PCR test by a nurse from the University of Maryland Medical System.
As of last week, over a three-week period Hirsch said the schools had tested 992 pools and 12,500 individuals. Sixty people were ultimately found to have the virus. The prevalence rate, Hirsch said, was 0.5%.
“What’s most newsworthy is we are not seeing transmission,” Hirsch said. “We’re not seeing those cases spread. It shows that masking, social distancing and air filters are working.”
She said each pooled test costs about $150.
Massachusetts has implemented similar pool testing, with more than half its public schools participating and more joining all the time, according to Russell Johnston, a senior associate commissioner for the state Department of Elementary and Secondary Education and its lead on the testing program.
The pool approach uses PCR tests, while the individual tests use the antigen tests. If, after a positive PCR pool test, the individual antigen tests don’t produce a positive result for anyone in the pool, Johnston said, then everyone is given a PCR test.
So far, few cases have been detected. The positivity rate for the pools is 0.76%, Johnston said. An average of about two people in the school testing program out of a thousand have been found to have the virus.
Massachusetts is picking up all the costs of the school testing, Johnston said, relying in part on money from Biden’s relief bill.
While there may be holes in testing protocols that still result in false positives and negatives, Linda Mendonca, president-elect of the National Association of School Nurses, said testing can be a useful part of a school system’s public health strategy.
“It’s what the CDC talks about, taking a Swiss cheese approach,” she said. “Masking, distancing, air circulation. You have to do all these layers. Testing is just one more to add in.”
Michael Ollove is a staff writer at Stateline.