Why Trump’s Rapid-Testing Plan Worries Scientists

The sun was beaming, the air was clear, and it seemed as if President Donald Trump was finally taking coronavirus testing seriously. Standing in the White House Rose Garden early last week, Trump announced to buoyant officials that a “massive and groundbreaking expansion” in testing was under way: The federal government had purchased 150 million new coronavirus tests from the company Abbott Laboratories.

These new rapid tests were “from a different planet,” Trump boasted. He was right. Each Abbott test cost only $5, one-20th the price of the most widely used test type. Instead of taking hours to deliver a result, the Abbott tests—which detect viral proteins—could provide an answer within 15 minutes. The government planned to send them to states, colleges, and nursing homes, a policy that would “more than double the number of tests already performed,” Trump said.  

Every state could, “on a very regular basis, test every teacher who needs it,” he promised.

As Trump spoke, the coronavirus was already teeming through his body, information from his doctor now suggests. By the end of the week, the president, the first lady, and at least 23 of his advisers and staff were infected with the coronavirus. They had acted as if testing alone would protect them, but many of them seem to have been infected at a White House event where Abbott tests were used to screen visitors.

This series of events could have ended another way, with tests such as Abbott’s allowing Americans to recapture a shred of normal life. But it has instead opened to public view an already-ferocious debate among experts about the best way to defeat the pandemic—a fight with consequences that will outlast Trump’s symptoms.

Read: The president is not well

Since the spring, a group of experts led by Michael Mina, an epidemiology professor at Harvard, has called for the government to freely distribute tens of millions of 15-minute coronavirus tests a day. Never mind testing every teacher every day: Mina wants to test nearly every American every day, whether or not any given person shows symptoms of COVID-19. That’s impossible to do with the gold-standard reverse-transcription polymerase chain reaction, or PCR, tests—they are too expensive and take too long to return results. Frequent, cheaper testing, Mina claims, could defeat the pandemic within weeks, as infectious people are identified and quarantined. (We wrote about his plan in August.)

Other experts are doubtful and have warned that cheap, rapid tests will not work as promised. If distributed en masse and used to screen asymptomatic people, these antigen tests will deliver hundreds of thousands—if not millions—of false results, they say. False negatives could lead to reckless behavior by people who don't know they're sick. False positives can also put people at risk: If a virus-free nursing-home resident with a false positive is placed in a COVID-19 ward, that person could become infected.

“The point I'm trying to make here, and I'll be blunt, is that antigen testing will not and cannot work for asymptomatic screening, and [it] will probably kill a lot of people,” Geoffrey Baird, the acting laboratory-medicine chair at the University of Washington, told us. His lab at UW developed one of the earliest accurate COVID-19 tests in the U.S., and is widely respected within the diagnostic-testing field. Alexander McAdam, the director of the infectious-diseases diagnostic laboratory at Boston Children’s Hospital, told The New York Times that deploying the current antigen tests to screen populations “is a bad idea, and I’ll die on that hill.”

The stakes of this dispute are not only how Abbott tests are used, but whether they should be used at all. It could shape federal policy next year and determine whether more money is spent on fixes to address the virus aside from a vaccine. Already, this conflict is playing out on the state level. In Nevada, public-health authorities have told nursing homes to stop using two models of antigen-test machines, which the federal government has sent to more than 14,000 facilities, after only 16 of 39 positive tests were confirmed by subsequent PCR testing.

Read: This overlooked variable is the key to the pandemic

What everyone agrees on is that the tests were not deployed responsibly at the White House. The president hosted dozens of guests at a ceremony honoring Supreme Court nominee Amy Coney Barrett, without masks, amid a raging pandemic, and rejected some of the most basic safety protocols. As that event has demonstrated, testing must be an and strategy, not an or one. Rapid testing and masking. Rapid testing and social distancing. Rapid testing and vaccines.

“Testing is a belt-and-suspenders approach that adds incremental safety,” Baird said. “Belts and suspenders only work, though, when you are wearing pants.”

The president also seems to have personally rejected testing for himself. Trump’s doctor has persistently dodged questions about when the president last tested negative. The New York Times reported that Trump—who officials once claimed was tested “multiple times a day”—was not swabbed even once a day.

The debacle has accelerated preexisting concerns about the rollout of the Abbott tests. Late last month, even the proponents of rapid testing worried about the plans to distribute and use the Abbott tests. Mina, generally an advocate of rapid testing, warned that if the Abbott tests were not deployed the right way, with the proper safeguards and solid public education, they could further erode trust in the nation’s public-health systems. The White House's cavalier actions have now realized that fear.

These tests have the potential to create two problems. One is commonly cited by critics and very easy to understand: False negatives will give people too much confidence that they are virus-free, just like the White House attendees who drank and celebrated together without masks, even hugging one another. Given a negative test result, many people chose to eschew the simple precautions that have helped slow the spread of the virus.

The other problem is that these tests will generate many false positives, especially if deployed in asymptomatic populations where relatively few people are sick. It could very well be that, as in Nevada, the majority of positive test results are false. Besides the risks of grouping healthy people with those who are actually sick, false positives will keep well people home from work unnecessarily and prompt people to seek “confirmatory” PCR tests, potentially overwhelming an already fragile system.

Mina and other proponents argue that rapid antigen tests could still be useful with their current performance, but that distribution and communication must be improved. “If these tests are not messaged appropriately, we run the risk of the whole program coming crashing down pretty much immediately,” Mina told us.

Read: How we survive the winter

The early signs are not encouraging. The new Abbott test, the Binax NOW, received an emergency use authorization (EUA) based on results from just 102 samples. The next day, the government spent $760 million to buy the entire supply of tests. Notably, the FDA did not support the use of the test for screening asymptomatic people—which the most ambitious version of Mina's plan depends on. The emergency use authorization only covered testing for people within the first seven days of developing symptoms, when viral loads remain high.

In asymptomatic people, the tests will likely perform worse. The levels of virus are likely to be lower in any individual infected person, which would increase the false-negative rate. And in the general, symptom-free population, the expected levels of infection are actually quite low, so the false-positive rate could be very high.

Yet Admiral Brett Giroir, the administration’s “testing czar” and an assistant secretary at the U.S. Department of Health and Human Services, has explicitly said that the tests could be used for asymptomatic screening, at schools perhaps.

That contradiction worries Baird. “One branch of the government is saying, ‘Use this test for asymptomatic people,’ and then on the other side, they are saying, ‘Use this test for symptomatic people,’” he said.

Baird is particularly anxious that the performance of tests will deteriorate in the field and when applied to asymptomatic people. That always happens with lab tests, he told us. “They haven’t published clinical-trials data,” he said. “You foist that test on the public after collecting evidence that it would work.”

False positives worry Mina, too. Among people tested within the first seven days of showing symptoms, the Abbott test will, according to its EUA, generate a false positive from roughly one in 50 tests. Because relatively few people test positive out of the whole population, those false positives could represent a large percentage of the positive results that a batch of the tests would generate. For now, the solution is supposed to be for people who test positive to get a confirmatory PCR test. But “saying that these tests need to be confirmed with a PCR test isn’t a good answer,” Mina told us. If a “quick” positive result then forces people to wait four days for a PCR positive, the first result stops meaning much.

Mina suggests that a cornucopia approach could provide the answer: If you take an Abbott test and get a positive result, then you would take another quick test, made by a different company, that detects a different viral protein, for confirmation. He said that such procedures were common in screening for relatively rare diseases, such as HIV, where the Centers for Disease Control and Prevention issues an “algorithm” for sequencing tests.

“People are just thinking about COVID testing differently for some reason, but imperfect screens are pretty common, so I am scratching my head,” says Dan Larremore, a computer scientist and an infectious-disease modeler at the University of Colorado, who has collaborated with Mina. “The perfect has really been the enemy of the good here, in many ways—except that we also know how to embed the good within follow-up systems to make it nearly perfect.”

Mina is running a trial comparing PCR and antigen tests in both symptomatic and asymptomatic people, in order to generate real-world data about false positives and negatives. “My hope is that six weeks from now, we’ll have a pretty good set of data to reflect the performance,” he said.

He still thinks these quick, cheap tests could help America overcome the pandemic. “The point people are really missing is: What is the alternative? The alternative is no testing. Most K–12 students are not getting tested,” Mina said. “Every time we can pull a positive person out of the population, we stop tens, hundreds, or thousands of cases.”

The alternative for Baird is obvious: keep going with the behavioral interventions that have helped at least slow the spread in the U.S. “I think the quintessential problem in the country is an imbalance of supply and demand of testing,” Baird said. “Mina’s solution is increasing supply. And I have a strong belief that decreasing demand will be the way to get there—masking, physical distancing, not having large events. And, unfortunately, absorbing the societal toll that all of those things take.”

While the surface of the debate is about the technological characteristics of these tests, the substance of it is about human behavior. As restrictions on daily life enter their seventh full month and winter draws near, will the countermeasures that have limited, but never contained, the virus’s spread remain in force? And if we add tests that generate imperfect information, will that embolden people to abandon commonsense safety precautions? No test—and no testing strategy—is perfect; we are living through a pandemic, and people will get sick. To believe that antigen testing can improve life in this country is to believe that people will understand the limits of a test result and act accordingly. With the right public messaging, perhaps they could.