WASHINGTON — Cheap coronavirus tests that ordinary Americans can administer at home, without either a prescription or any medical expertise, could significantly drive down infection rates, say researchers from the University of Colorado and Harvard. Their findings counter long-standing concerns that rapid tests are less accurate than those that are sent to laboratories.
Those inaccuracies become effectively inconsequential if enough rapid tests are done with sufficient frequency, their statistical models indicate.
“The critical finding of our work is that when it comes to screening tests for COVID, turnaround time is absolutely critical,” said Daniel Larremore, a computer scientist at Colorado. “That’s because stopping transmission requires telling people they’re infected early, so they can protect the people around them.”
Another of the study’s authors, Harvard epidemiologist Michael Mina, told a Boston-area radio station that if “we could have 10 to 20 million of these tests every single day across all of America, that would be enough to stop the outbreaks across the United States” in just a few weeks’ time, without the need for onerous statewide and citywide lockdowns.
That is because those rapid tests would catch many people who may be infectious but are not actually sick. About 30 percent of people show no signs of the virus at all but are still capable of spreading it, potentially sickening or killing others. Those people may not ever see the need to wait in a long line to have a long swab jabbed into the nasal cavity. But they could potentially be persuaded to apply mucus to a paper strip in the privacy of a home bathroom.
Some airlines have begun to offer rapid testing at gates to keep their aircraft from becoming transmission sites.
The nation does not have anywhere near the capacity for rapid testing that advocates of the method believe is necessary. The Trump administration has started distributing 150 million rapid BinaxNOW tests. So far, about 63 million of those tests have been shipped either to governors or directly to sites like nursing homes. But many more tests would be needed for the kind of daily volume Mina envisions.
The administration has invested $238 million in rapid antigen testing, according to statistics compiled by the Department of Health and Human Services. Last week, the Food and Drug Administration approved the first rapid test available for home use. The test does require a prescription, and the biomedical company that created it, Lucira, is charging $50 for each one.
“Great first step, but the price point of $50 concerns me,” Advancing Health Equity founder and chief executive Dr. Uché Blackstock told Yahoo News.
Harvard epidemiologist Mina envisions rapid tests that cost as little as $1.
Rapid tests are also called antigen tests because they look for proteins attached directly to the virus. They tend to catch people when they are most infectious, including in the days right before symptoms develop. Results take as little as 15 minutes. Many have compared the entire antigen testing process (at least in its ideal form) to the kind of pregnancy test available in any American pharmacy.
Molecular tests (also called PCR tests, for “polymerase chain reaction”) are more accurate than antigen tests, but they need to be processed in a laboratory. That used to take as long as two weeks. Even now, molecular tests require at least two days of processing.
For months, researchers have preferred molecular tests over antigen tests, stressing accuracy over speed. But that is the wrong approach, the researchers in the new paper say.
“It turns out that a fast turnaround time is actually more valuable than super-high sensitivity,” Larremore, the University of Colorado computer scientist, told Yahoo News.
Dr. Anthony Fauci, the nation’s leading voice on the coronavirus pandemic, told Yahoo News that while molecular tests remain the best way to tell if an individual is sick, making broader, community-wide assessments — a concept known as “surveillance testing” — is easier done with a rapid test.
“If you repeatedly do surveillance, we know you can make up for a relative lack of exquisite sensitivity of the test,” Fauci told Yahoo News. “And even in the tests that are not sensitive, what you might see is that you might miss someone who is, strictly speaking, positive, but the level of virus is so low in them that they’re not going to transmit.”
People can transmit the virus before they actually start to show symptoms. This kind of asymptomatic spread has proved especially vexing to public health officials. It also appears to be precisely the problem the Colorado and Harvard research seems to address.
In one of the models described in the new study, the researchers envisioned a scenario in which 4 percent of New York City’s 8.4 million residents tested positive for the coronavirus. That scenario could soon become reality, with New York having shuttered its public schools after reaching 3 percent test positivity, the threshold for such a closure.
Their model showed that if people were tested quickly, they would stay home and prevent the spread of the virus, even if they themselves never got sick. “We found that testing 75% of individuals every 3 days was sufficient to drive the epidemic toward extinction within 6 weeks,” the researchers wrote. By that time, the infection rate would have fallen by 88 percent.
By contrast, if people took molecular tests instead, infection would decrease by 58 percent during the same period. That is because some infectious people would continue to unknowingly spread the virus as they waited for their results.
“Delays in reporting lead to dramatically less effective control of viral spread,” the authors wrote in their study, which was published in the academic journal Science Advances late last week. Getting results quickly, and testing frequently, they argue, compensates for inaccuracies in those results. And in a pandemic that is killing some 1,500 people in the United States on a daily basis, waiting several days for somewhat more accurate results — that is, the molecular tests sent off to labs — is not good public health policy, they say.
“This paper is one of the first to show we should worry less about test sensitivity and, when it comes to public health, prioritize frequency and turnaround,” said one of the study’s authors, Colorado biochemist Roy Parker.
It is not clear how much of a priority rapid testing is for the incoming Biden administration — transition officials did not return several Yahoo News requests for comment. Biden has said he wants to implement a national testing strategy, but details remain inchoate.
No such strategy has been evident from the Trump administration, though the testing situation is much better than it was in the spring. It is still far from what public health experts like Mina envision, in part because the president lost interest in the pandemic months ago, but also because the nation’s production capacity remains strained.
Earlier this fall, Yahoo News asked Adm. Brett Giroir, the White House coronavirus task force official in charge of testing, when rapid coronavirus testing would be available to Americans on a daily basis. He dismissed the notion as “utopian.”
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