F.D.A. Authorizes First At-Home Coronavirus Test

The Food and Drug Administration on Tuesday gave an emergency green light to the first rapid coronavirus test that can be run from start to finish at home, paving a potential path for more widespread testing outside of health care settings.

The test, developed by the California-based company Lucira Health, requires a prescription from a health care provider, and people under the age of 14 also cannot perform the test on themselves.

But with a relatively simple nasal swab, the test can return results in about half an hour, and it is projected by the company to cost $50 or less, according to the product’s website. Clinicians can also run the test on their patients, including children younger than 14, potentially delivering results during a single visit to a care center or pharmacy instead of routing a sample through a lab.

A handful of other tests have been given emergency authorization by the F.D.A. for at-home collection of samples, which are then shipped to a lab for processing. But Lucira’s test is the first to remove the need for an intermediary.

“Today’s authorization for a complete at-home test is a significant step toward the F.D.A.’s nationwide response to Covid-19,” Jeff Shuren, director of the F.D.A.’s Center for Devices and Radiological Health, said in a statement. “Now, more Americans who may have Covid-19 will be able to take immediate action, based on their results, to protect themselves and those around them.”

People who test positive for the coronavirus are advised to isolate themselves from others for 10 days starting from the onset of symptoms or from the day they tested positive, per guidelines from the Centers for Disease Control and Prevention.

Laboratory tests that look for the coronavirus’s genetic material using a technique called polymerase chain reaction, or P.C.R., are still considered the gold standard for detecting the virus. But the new at-home test relies on similar principles, using a method called a loop-mediated isothermal amplification reaction, or LAMP. Like P.C.R., LAMP repeatedly copies the virus’s genetic material until it reaches detectable levels, enabling the test to identify the virus even when present at only very low levels in the respiratory tract. LAMP is faster and less cumbersome than P.C.R., but is generally thought to be less accurate.

People taking the battery-powered test must swirl a swab in both nostrils, then dip and stir the swab into a vial of chemicals. That vial is then plugged into a test cartridge that processes the sample. Within a half-hour, the test cartridge will light up as “positive” or “negative.” Federal guidelines note that people taking the test should report the results to their health care providers, who must then inform the public health authorities to help track the virus’s spread.

An at-home test for the virus “was going to happen,” said Omai Garner, a clinical microbiologist and diagnostics expert at the University of California, Los Angeles Health System. “I am hopeful that it works well.”

Dr. Garner added that the news should be taken with a note of caution. In recent months, several experts have called for more widespread at-home testing as a way to help curb the virus’s spread. But others have raised concerns about the practicality of a strategy that would most likely rely on tests that sacrifice a degree of accuracy for convenience and a more affordable price tag.

According to the product’s instructions, Lucira’s LAMP test was able to accurately detect 94.1 percent of the infections found by a well-established P.C.R.-based test. It also correctly identified 98 percent of the healthy, uninfected people. The study, which was conducted by the company, was small, and included only people who had symptoms of Covid-19, the disease caused by the coronavirus. The packaging for the test notes that it “has not been evaluated” in asymptomatic people.

Although the company has yet to release more detailed results on its product’s performance, “the data look good” and could enable the test to fill an important gap, said Susan Butler-Wu, a clinical microbiologist at the University of Southern California. One of the most serious issues bedeviling efforts to identify people infected by the coronavirus is the inconsistent access to reliable laboratory testing in many parts of the country, especially outside urban centers.

“This type of assay can play a big role there,” Dr. Butler-Wu said.

Representatives at Lucira Health did not respond immediately to requests for comment.

Saskia Popescu, an infection prevention expert and epidemiologist at George Mason University, cautioned that home testing, while a notable advance, is not a panacea. “No test is perfect,” she said, and a negative result should not be taken as a free pass to mingle. Moreover, testing alone cannot prevent the spread of disease, and must be combined with other public health measures like physical distancing and masking, she added.

Dr. Popescu also expressed concern at the vagueness around reporting results. At-home testing adds another degree of separation to the reporting process, which would need to include communications between patients and their health care providers, then a follow-up between those health care providers and public health officials.

The merits and pitfalls of at-home testing should continue to be weighed, Dr. Popescu said, adding: “We need more accessible and fast lab-based testing.”

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