Rapid coronavirus tests alone don't prevent outbreaks, a CDC study shows. The White House relied on them anyway.
- The White House relied on rapid molecular
coronavirustests to determine whether event attendees were infected, while deemphasizing mask wearing and social distancing.
- Experts say the tests shouldn't be the sole precaution and can't be used as a pass to safely get close to other people.
- A new CDC study reveals that another type of rapid test – antigen tests, which can deliver results in as little as 15 minutes — can more often give a false negative than traditional PCR tests.
- The study results came just four days after President
Trumptested positive, part of a White House coronavirus outbreak that has hit at least a dozen people.
The White House has not required staff or event attendees to wear masks or social distance throughout the pandemic.
Instead, the main precautionary measure the Trump administration relied on was rapid molecular tests, which work by identifying a small section of the virus' genome and amplifying it until it's detectable.
Specifically, the administration has used Abbott Laboratories' ID Now rapid test to determine whether those coming into contact with the president were coronavirus-free. That was the case on September 26, when President Trump hosted the Supreme Court nomination ceremony for Judge Amy Coney Barrett in the Rose Garden. All guests were tested before attending; then, comfortable that all results were negative, maskless guests hugged, mingled, and remained in close proximity to one another over the course of at least 20 minutes.
Less than a week later, Trump had
New research from the Centers for Disease Control and Prevention suggests that the White House's reliance on rapid tests in these instances may have been unsafe. A CDC study published Monday describes a case in which a 13-year-old was exposed to the virus, tested negative using a rapid test, then vacationed with her family.
The teenager's result turned out to be a false negative, and she ended up passing the illness on to a dozen family members.
Rapid tests are faster but less accurate
Rapid diagnostic tests for the coronavirus, unlike the traditional RT-PCR tests that get sent to a lab, can take as little as 5-15 minutes to yield results.
Most of these fast-turnaround tests – including the test the 13-year-old used – look for antigens, bits of protein that sit on or in the virus. Molecular tests, like Abbott's, hunt down pieces of the virus' genome. By contrast, the PCR tests do a more in-depth scouring for the virus's genetic code, which is why it often takes days to get results.
The problem with speeding up the process, however, is that many of the antigen rapid COVID-19 tests we have now may only pick up about 70% to 80% of infections, and they can produce false negatives. The Food and Drug Administration cautions that negative rapid-test results may need to be confirmed with a lab test, and the CDC says the tests are "generally less sensitive than viral tests."
Molecular tests are better, but they still aren't as accurate as PCR tests. Some studies have found that about 9% of Abbott ID Now tests produce false negatives. PCR tests, on the other hand, "would be pretty close to 100% accurate" if performed correctly, Dr. Emily Volk, an assistant professor of pathology at the University of Texas-Health in San Antonio, told Healthline.
"What seems to have been fundamentally misunderstood in all this was that they were using it almost like you would implement a metal detector," Ashish Jha, dean of Brown University's School of Public Health, told the Wall Street Journal, adding, "a metal detector that misses 10% of weapons — you'd never, ever say that's our only layer of protection for the president."
In an email to Business Insider, John Koval, an Abbott spokesperson, noted that "more than 11 million Americans have taken the ID NOW test, helping to stop the spread of the virus."
"Rapid tests are an invaluable tool that help reduce the risk in society and slow the spread of the virus," he added. The goal should be to test often – or if that's not possible, to test if you've been exposed or have symptoms – and find out if you have it. If so, you'll know to isolate to prevent spread."
A family gathering gone awry
The new CDC study describes a family that put their faith in rapid antigen testing. Among 14 people who stayed in one house together following the teenage family member's negative test result, 12 contracted COVID-19.
The 13-year old had been exposed to the coronavirus while away from home, and she was experiencing nasal congestion but no other symptoms when she took the rapid test. After her negative result, the family deemed it safe for her to travel to the five-bedroom, two-bathroom vacation house with the group.
The family members staying at the house did not wear masks or practice social distancing, though six other relatives who visited the family gathering remained outdoors and socially distanced. Those six people did not get infected.
"I would still say that distancing and outdoor air are your best friends," Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, previously told Business Insider. "To me, that would provide me much more assurance that I was not going to either get infected, or infect others, than would a rapid-detection test."
Based on their results, the CDC study authors said the case study shows why "regardless of negative test results, persons should self-quarantine for 14 days after a known exposure." They also reiterated that results of rapid antigen tests need to be confirmed with PCR tests, especially in people "with high pretest probability of infection, such as those with a known exposure."
When rapid tests can be useful
While they shouldn't be the only precaution people take, rapid tests can help screen large groups for the coronavirus, according to Anne Wyllie, a researcher behind the rapid saliva-based test SalivaDirect, which got emergency FDA authorization in August.
"This is definitely more for screening," Wyllie previously told Business Insider. She added that the tests could be useful for "frequent testing" in group settings like schools and workplaces.
Still, it's easy to see how the tests can foster a false sense of security.
"It does send a message basically that if you're negative at this point, you must be doing something right," Osterholm said. "When I would say [if] you're negative at this point, you might just be lucky, and your luck's going to run out."
Correction: A previous version of this story noted that the White House had relied on rapid antigen tests. It has actually been using Abbott's rapid molecular tests.
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