New At-Home Covid Test Gets Green Light From F.D.A.

The Food and Drug Administration on Tuesday issued an emergency authorization for the country’s first coronavirus test that can run from start to finish at home without the need for a prescription.

People as young as 2 years old are cleared to use the test, which takes just 15 to 20 minutes to deliver a result. Unlike many similar products, which are only supposed to be used by people with symptoms of Covid-19, this test is authorized for people with or without symptoms.

The test, developed by the Australian company Ellume, detects bits of coronavirus proteins called antigens. It’s slightly less accurate than gold standard laboratory tests designed to look for coronavirus genetic material with a technique called polymerase chain reaction, or P.C.R. But in a clinical study of nearly 200 people, Ellume’s product was able to detect 95 percent of the coronavirus infections found by P.C.R., regardless of whether the infected people felt sick. It also correctly identified 97 percent of the people who received negative laboratory test results.

Ellume, which was awarded a $30 million grant from the National Institutes of Health, said it planned to manufacture and deliver about 20 million home coronavirus tests to the United States within the first half of 2021. Each kit, which tests a single swab sample, is expected to cost about $30 or less, said Bella Zabinofsky, a spokeswoman for the company.

In a statement, the F.D.A. commissioner Dr. Stephen M. Hahn called Ellume’s authorization “a major milestone in diagnostic testing for Covid-19” in light of the coronavirus’s persistent grip on the nation. The product will be available in drugstores, Dr. Hahn noted, and gives Americans “more testing options from the comfort and safety of their own homes.”

Ellume’s test works best in people with Covid symptoms. In people without symptoms, the product’s accuracy dropped a bit, finding 91 percent of the coronavirus infections discovered by P.C.R.

Dr. Valerie Fitzhugh, a pathologist at Rutgers University, noted that all of the study’s false positives occurred in the asymptomatic group. That “does make me a little nervous,” Dr. Fitzhugh said. False positives could send people into unnecessary periods of isolation or erode trust in testing, among other issues.

In a statement announcing Ellume’s emergency clearance, the F.D.A. underscored the importance of recognizing false positive and false negative results, both of which are more common with antigen tests. People without symptoms who test positive, the agency said, should confirm their results with another test, especially if the coronavirus is scarce in their community. When very few people in a region are infected, the number of false positives yielded by tests can outnumber true positives.

Still, in broad strokes, “the performance looks better than what we’ve seen for other antigen tests,” said Susan Butler-Wu, a clinical microbiologist at the University of Southern California’s Keck School of Medicine.

The test’s price tag — compared with some competitors that cost just $5, for example — and limited availability will likely restrict it from very frequent use, Dr. Butler-Wu said. But in single-use contexts, “what’s really exciting is, it allows me to get a really quick answer if I’m feeling unwell. To me, that’s the most powerful thing.”

The Coronavirus Outbreak ›

Words to Know About Testing

Confused by the terms about coronavirus testing? Let us help:

    • Antibody: A protein produced by the immune system that can recognize and attach precisely to specific kinds of viruses, bacteria, or other invaders.
    • Antibody test/serology test: A test that detects antibodies specific to the coronavirus. Antibodies begin to appear in the blood about a week after the coronavirus has infected the body. Because antibodies take so long to develop, an antibody test can’t reliably diagnose an ongoing infection. But it can identify people who have been exposed to the coronavirus in the past.
    • Antigen test: This test detects bits of coronavirus proteins called antigens. Antigen tests are fast, taking as little as five minutes, but are less accurate than tests that detect genetic material from the virus.
    • Coronavirus: Any virus that belongs to the Orthocoronavirinae family of viruses. The coronavirus that causes Covid-19 is known as SARS-CoV-2.
    • Covid-19: The disease caused by the new coronavirus. The name is short for coronavirus disease 2019.
    • Isolation and quarantine: Isolation is the separation of people who know they are sick with a contagious disease from those who are not sick. Quarantine refers to restricting the movement of people who have been exposed to a virus.
    • Nasopharyngeal swab: A long, flexible stick, tipped with a soft swab, that is inserted deep into the nose to get samples from the space where the nasal cavity meets the throat. Samples for coronavirus tests can also be collected with swabs that do not go as deep into the nose — sometimes called nasal swabs — or oral or throat swabs.
    • Polymerase Chain Reaction (PCR): Scientists use PCR to make millions of copies of genetic material in a sample. Tests that use PCR enable researchers to detect the coronavirus even when it is scarce.
    • Viral load: The amount of virus in a person’s body. In people infected by the coronavirus, the viral load may peak before they start to show symptoms, if symptoms appear at all.

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