The Food and Drug Administration has granted LabCorp an emergency use authorization to test people with no symptoms for the coronavirus, the first time the agency has authorized such a test in people without symptoms.
"FDA reissued the LabCorp COVID-19 RT-PCR Test EUA to expand use of the test to anyone, after the company provided scientific data showing the test's ability to detect SARS-CoV-2 in a general, asymptomatic population," the agency said in a statement last week.
Previously, to get a coronavirus diagnostic test, a person may have been asked to meet certain criteria, such as having symptoms of COVID-19, the disease caused by the coronavirus, or having had close contact with a person confirmed to be infected.
In a statement to NBC News, a spokesperson for LabCorp said that the test hasn't changed and that the company has simply been granted authorization to expand its use to those without symptoms.
At the same time, labs across the U.S. are experiencing testing backlogs due to overwhelming demand, leading to delays in the turnaround time for results.
Growing evidence suggests certain similarities in COVID-19 cases with and without symptoms.
In a study posted Monday to the preprint server MedRxiv, researchers from the Broad Institute of MIT and Harvard University found that the viral load — or the amount of virus in a person's body — was similar in those who tested positive for the coronavirus both with symptoms and without symptoms. (Studies posted to preprint servers haven't yet gone through peer review.)
The study looked at testing data from 32,299 residents and staff members at 366 skilled nursing facilities, nursing homes and assisted living facilities across Massachusetts.
Of the people who tested positive, 71 percent of residents and 93 percent of staff members didn't have symptoms at the time of testing, and the viral load was similar in those with and without symptoms.
The researchers suggested that polymerase chain reaction, or PCR, tests that have been validated to test symptomatic people should also be effective in those without symptoms, as is the case with LabCorp. (The research wasn't related to the LabCorp test, however.)
PCR tests work by detecting tiny bits of the virus' genetic material; the more virus that is present, the easier it is for the test to detect it. If levels of the virus are similar in people regardless of symptoms, the test should be equally effective.
Dr. Eric Topol, founder and director of the Scripps Research Translational Institute, said the findings were "very important."
The report "extends smaller previous ones as to the similarity in viral load in people without COVID-19 symptoms as compared with those having symptoms," said Topol, who wasn't involved with the new research.
However, he cautioned that, despite similarities in viral load, the study doesn't establish whether asymptomatic people spread the virus to the same degree as symptomatic people.
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Peter Beernink, an associate professor of infectious disease at the University of California, San Francisco, said the study was one of the more comprehensive examinations of viral load that he has seen, given the number of cases and the random sampling involved in the data collection.
One of the bigger limits of the study, however, was that it didn't differentiate between asymptomatic and presymptomatic infections, he said. When people are presymptomatic, they go on to develop symptoms, even though they didn't have them when they tested positive.
"They didn't have longitudinal samples from the same individuals — so they never knew whether somebody was going to become symptomatic," said Beernink, who also wasn't involved with the new research.
Still, the research shows the importance of widespread testing.
"It's really the case that you don't know who has the virus, and unless you do widespread testing, we can't really make a large impact on decreasing" levels in the population, Beernink said.
CORRECTION (July 28, 2020, 9:35 p.m. ET): A previous version of this article misspelled the last name of an associate professor at the University of California, San Francisco. He is Peter Beernink, not Beernick.