People exposed to the coronavirus may need to take up to three home tests, F.D.A. Said

Repeated testing, spaced two days apart, reduces the chance of false negative results, the agency noted.
The United States Food and Drug Administration on Thursday issued a new recommendation that asymptomatic people who use coronavirus antigen tests take at least three tests, each spaced 48 hours apart, to reduce the risks of missing an infection.
People who show symptoms of Covid-19 should take at least two tests, 48 hours apart, the agency says .
The new guidelines come as the highly transmissible BA.5 subvariant of Omicron continues to spread and after the Centers for Disease Control and Prevention has relaxed its recommendation for routine surveillance testing in most cases.
Many people have reported that home tests have failed to detect their infections, but studies have generally shown that a ntigen tests are as good at detecting Omicron as they were at detecting Delta, the worrying previous variant. Michael Mina, a former Harvard epidemiologist who is now the scientific director of eMed, which sells home tests. "Sometimes it takes two days for the virus to reach a detectable level and sometimes six days to grow."
Experts have long noted that rapid antigen tests, which are less sensitive than P.C.R. tests, are designed for serial use and are more likely to detect coronavirus when people take them repeatedly over several days.
The new recommendations emphasize the need for "additional testing over a longer period of time," the agency said.
"The F.D.A.'s new recommendations for testing Covid-19 antigen at home underscore the importance of repeat testing after a negative test result to increase the chances of detecting infection,” said Dr. Jeff Shuren, director of the Center for Devices and Radiological Health at the agency, in a statement.
The new guidelines are based on the results of a new national study, which has not yet been published in a scientific journal. The study, led by researchers from the Chan Medical School of the University of Massac husetts, focused on 154 people who tested positive for the virus by P.C.R. testing between October 2021 and February this year.
It found that among symptomatic people, two tests taken 48 hours apart detected 93% of infections. But the same test model detected only 63% of infections in asymptomatic people.
When people without symptoms took three tests, every other day, testing detected 79% of infections. .
"We provide data-based evidence on how to test when using rapid antigen tests," said Dr. Apurv Soni, Assistant Professor at UMass Chan Medical School, which conducted the research. "Testing timing is important."
Some people enrolled in the study had Delta infections, while others were infected with Omicron, the researchers said. .
"The fact that the tests can detect Omicron is an important point that cannot be overstated," said UMass Chan molecular biologist Nathaniel Hafer. Medical School and study author.
People who fear infection even after receiving two or three negative home antigen test results may continue to test, search for a P.C.R. more sensitive. test ...

Health Aug 13, 2022 0 45 Add to Reading List

People exposed to the coronavirus may need to take up to three home tests, F.D.A. Said

Repeated testing, spaced two days apart, reduces the chance of false negative results, the agency noted.

The United States Food and Drug Administration on Thursday issued a new recommendation that asymptomatic people who use coronavirus antigen tests take at least three tests, each spaced 48 hours apart, to reduce the risks of missing an infection.

People who show symptoms of Covid-19 should take at least two tests, 48 hours apart, the agency says .

The new guidelines come as the highly transmissible BA.5 subvariant of Omicron continues to spread and after the Centers for Disease Control and Prevention has relaxed its recommendation for routine surveillance testing in most cases.

Many people have reported that home tests have failed to detect their infections, but studies have generally shown that a ntigen tests are as good at detecting Omicron as they were at detecting Delta, the worrying previous variant. Michael Mina, a former Harvard epidemiologist who is now the scientific director of eMed, which sells home tests. "Sometimes it takes two days for the virus to reach a detectable level and sometimes six days to grow."

Experts have long noted that rapid antigen tests, which are less sensitive than P.C.R. tests, are designed for serial use and are more likely to detect coronavirus when people take them repeatedly over several days.

The new recommendations emphasize the need for "additional testing over a longer period of time," the agency said.

"The F.D.A.'s new recommendations for testing Covid-19 antigen at home underscore the importance of repeat testing after a negative test result to increase the chances of detecting infection,” said Dr. Jeff Shuren, director of the Center for Devices and Radiological Health at the agency, in a statement.

The new guidelines are based on the results of a new national study, which has not yet been published in a scientific journal. The study, led by researchers from the Chan Medical School of the University of Massac husetts, focused on 154 people who tested positive for the virus by P.C.R. testing between October 2021 and February this year.

It found that among symptomatic people, two tests taken 48 hours apart detected 93% of infections. But the same test model detected only 63% of infections in asymptomatic people.

When people without symptoms took three tests, every other day, testing detected 79% of infections. .

"We provide data-based evidence on how to test when using rapid antigen tests," said Dr. Apurv Soni, Assistant Professor at UMass Chan Medical School, which conducted the research. "Testing timing is important."

Some people enrolled in the study had Delta infections, while others were infected with Omicron, the researchers said. .

"The fact that the tests can detect Omicron is an important point that cannot be overstated," said UMass Chan molecular biologist Nathaniel Hafer. Medical School and study author.

People who fear infection even after receiving two or three negative home antigen test results may continue to test, search for a P.C.R. more sensitive. test ...