Why aren’t there fast COVID-19 tests?
Karen Weintraub
One major reason COVID-19 is raging out of control across much of the country: The current system of testing catches only a fraction of people while they are contagious.
It’s now clear as many as 40% of people who contract the coronavirus that causes the disease don’t know they have it. Others are contagious a few days before they know they’re sick. If more people knew when they were infectious, they would likely stay home and not pass on the virus, slowing or even stopping the outbreak.
But the test that’s most commonly used to diagnose COVID-19, known as a PCR test, requires analysis in a lab using expensive equipment. With the surge in cases in Southern and Western states and a shortage of supplies to run the tests, it routinely takes three to five days – often a week or longer – to return results.
More than 750,000 tests are done a day in the United States, and more than 50,000 new positives have been recorded nearly every day this month.
A growing chorus of scientists argue that while PCR may be a good tool in hospitals to identify precisely how much virus a patient is carrying, it’s not enough to stop the pandemic.
Instead, people need to know they’re contagious when they’re contagious, which means they should be tested at least a few times a week.
“That could be one of our most important interventions as we come into the fall to prevent large outbreaks from happening,” said Stephen Kissler, a research fellow at the Harvard T.H. Chan School of Public Health.
“I’m on board with (this) thinking,” said Dr. Benjamin Pinsky, medical director of the clinical virology laboratory at Stanford University. “I think that would be quite useful.”
Someone who tests negative could visit an aging parent or grandparent without worrying about risking their lives. Teachers could walk into their classrooms with confidence, knowing that no one was harboring the virus. The dental chair would become a little less scary.
“We still are not in a circumstance where we have quick turnaround diagnostics the way we need,” Dr. Francis Collins, director of the National Institutes of Health said in Friday webinar.
Faster, cheaper, easier
A rapid, low-cost diagnostic is technologically feasible and getting closer to reality.
At Massachusetts Institute of Technology, researchers are collaborating with a team at 3M to develop and scale such a test. Before the pandemic, MIT chemical engineer Hadley Sikes had developed prototypes to detect malaria, tuberculosis and dengue.
If one for COVID-19 works, it could deliver results within 10 minutes. All someone would need to do is add a bodily fluid to a specially made piece of paper that changes color to indicate a positive or negative – no formal training or fancy machines needed.
The National Institutes of Health is supporting development of this test and others with money, daily advice and a “Shark Tank”-like competition, Sikes said. It’s part of a $1.5 billion federal initiative called Radical Acceleration of Diagnostics (or RADx) to speed the pace of diagnostic development.
“The world needs as many useful tests as possible as fast as possible,” Sikes said.
Her team’s goal is to develop millions of these pregnancy-test-like diagnostics every day, first in the United States and then around the world. Although Sikes said she couldn’t commit to a specific timeline, theoretically, tens of millions of such tests could be produced in time for the start of school in September.
How much does accuracy matter?
An early review of this type of rapid test showed it accurately identified people with COVID-19 only about half the time. But it was the right half, said Dr. Michael Mina, an assistant professor of epidemiology at Harvard T. H. Chan School of Public Health, who has been leading the effort to develop a fast, frequent testing approach.
This test might miss some people with low levels of virus in their system, but most of those would already be on the road to recovery, with such low levels they’d unlikely be contagious.
Whether you’re infectious or not depends on how much virus your body is producing, Sikes said.
As someone is falling ill, the virus reproduces incredibly quickly, so they wouldn’t stay at low levels for more than a few hours, Mina said on a recent This Week in Virology podcast. Odds are slim the person would test themselves in that exact window and miss a burgeoning infection.
And even if the test overlooked a few infected people, another test a few days later when they are more infectious would almost certainly be positive, Mina said.
Dave O’Connor, a professor of pathology and laboratory medicine at the University of Wisconsin-Madison, said tests can miss lots of people with low levels of the virus and yet have a profound impact on transmission.
“You’ll still have some embers” with a rapid, less accurate test, O’Connor said. But much of the COVID-19 transmission seems to come from super-spreaders – people with extraordinarily high viral loads in a position to infect a lot of other people. “If that’s correct, then those are the people you’ll need (to identify) to extinguish much of the fire.”
And a rapid test taken frequently should be able to do that.
There would still be a role, O’Connor and others said, for PCR testing, in doctor’s offices and hospitals, where a precise diagnosis could be crucial for treatment. Other types of tests are also in use or under development, each with strengths and weaknesses, suitable in different contexts, said Stanford’s Pinsky, who is developing another type of test, as is O’Connor.
Waiting on regulatory approval
A big hang-up now is that regulators haven’t yet signed off on this type of rapid test, out of concern for its accuracy. And companies are not pursuing approval for such tests, because they don’t think the FDA will give its approval, Mina said.
“No one is stepping forward because the message they are receiving clearly from the FDA is that the tests must approach the analytical sensitivity of PCR,” he said. “But this should not be the criteria. It neglects how the tests are used.”
For its part, the U.S. Food and Drug Administration said it has approved six so-called point of care (POC) tests, which return results quickly – though these cannot be done without a lab or a trained professional.
“For accuracy/sensitivity of POC tests, the FDA remains committed to facilitating the availability of reliable, efficient diagnostic tests for COVID-19,” said FDA spokeswoman Nicole Mueller. “The agency considers the level of sensitivity in connection with the potential benefits and potential risks of any diagnostic test when evaluating an (Emergency Use Authorization) request.”
Daniel Larremore, a co-author with Mina on the paper reviewing the tests, said regulators may be particularly leery of allowing less sensitive tests because of criticism they faced earlier in the pandemic. To try to relieve a logjam of testing in March, the FDA opened the door to more than 200 antibody tests, later recalling authorization for many that proved useless.
“There may be some scars there from the past decision,” said Larremore, a mathematician and assistant professor at the University of Colorado Boulder’s Biofrontiers Institute.
The FDA’s rules are well-intentioned, said O’Connor, but providing the highest quality of data may not be as important when so many people are sick and suffering.
“The enormous burden of cases right here and now and the impact it’s going to have on society, especially when schools have a tough time reopening, demands innovation, demands creativity, and demands that the government enable types testing and types of novel approaches that might never be considered under other, non-pandemic situations,” he said.
Nate Grubaugh, an assistant professor of epidemiology at Yale University, said it’s unlikely enough rapid tests could be made quickly enough to transform the pandemic. And he worries that while each individual test would be lowcost, doing them repeatedly would end up being expensive, creating another disparity between poor and wealthy communities.
Fundamentally, “speed and availability of testing need to go up dramatically across the country,” said Grubaugh, who is developing a test that relies on saliva instead of sampling from the upper nose as is done with PCR tests. “It’ll be a combination of lots of things that get us there.”
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.