As demand for COVID-19 tests remains high and the omicron variant continues to drive a surge in infections, many are wondering how effective rapid antigen tests are.

The at-home rapid antigen tests are designed to detect a portion of protein — known as an antigen — of COVID-19, according to Nathaniel Hafer, a molecular biologist based at the University of Massachusetts Chan Medical School. The tests use a sample from your nose or mouth using a swab and provide results quickly, usually within 15 minutes.

Health experts explain how accurate the tests are, what symptoms to expect if infected, and what to do if you test positive but are asymptomatic.

How effective is the rapid antigen test at detecting omicron?

With appointments for the more-reliable PCR testing often hard to find, many people are turning to the at-home rapid tests for peace of mind.

» READ MORE: Where to get a free COVID-19 test in Philadelphia

But, the Food and Drug Administration recently reported a decrease in sensitivity in rapid antigen tests when it comes to detecting the variant cases, said Judith O’Donnell, the chief of infectious disease at Penn Presbyterian Medical Center.

“If you were trying to do a rapid antigen test for COVID-19 and you have omicron, you may be someone less likely to get a positive test,” O’Donnell told The Inquirer.

Despite the higher likelihood that a test result may not be accurate, O’Donnell said that doesn’t mean the antigen tests are not worth taking. People experiencing COVID symptoms — or people who have had a known exposure to the virus and are experiencing symptoms — can still test at home. But those experiencing symptoms who have taken two negative at-home tests should get a PCR test to confirm that they’re negative, she said.

Health experts say that if you do test positive, you should trust the rapid antigen tests.

“Due to the significant volume of people requesting COVID-19 tests, we are asking people who have tested positive using a home test to trust that result and isolate for five days as recommended by the CDC,” Cooper University Health Care said in a statement. “Given the high number of actual positive COVID-19 cases in our region, you can trust your positive home test result and save yourself from waiting on long lines to be retested allowing others to be tested.”

What should you do if you test positive but have no symptoms?

On Monday, the Centers for Disease Control cut the isolation restrictions for asymptomatic people who test positive for the coronavirus from 10 to five days.

» READ MORE: The CDC updated COVID-19 isolation guidelines. Here’s what you need to know.

The CDC also shortened the time that close contacts need to quarantine. Health officials officials said the guidance is in keeping with growing evidence that people with the coronavirus are most infectious in the two days before and three days after symptoms develop.

The isolation rules are for people who are infected. They are the same for people who are unvaccinated, partly vaccinated, fully vaccinated, or boosted.

The new CDC rules are:

  • The clock starts the day you test positive.

  • An infected person should go into isolation for five days, instead of the previously recommended 10.

  • After five days, if you have no symptoms, you can return to normal activities but must wear a mask everywhere around others, even at home, for at least five more days.

  • If you still have symptoms after isolating for five days, stay home until you feel better and then start your five days of wearing a mask at all times.

How severe will symptoms be if you test positive for COVID-19?

People who have been vaccinated and are healthy, especially those who have been boosted, are less likely to develop severe infections from the omicron variant and won’t likely end up in the hospital, according to medical experts who have monitored the effects of the variant.

» READ MORE: What are the symptoms of omicron? Here’s how they differ in vaccinated and unvaccinated patients.

While omicron has sent U.S. infections soaring to levels not seen since last winter’s wave, cases are often have less severe than the delta variant, according to a handful of international studies and early data from several U.S. hospitals.

Those infected by the omicron variant are 15 to 20% less likely to go to an emergency room, and 40% less likely to be hospitalized overnight, compared with those infected with delta, according to English data analyzed by scientists from Imperial College London. That aligns with early U.S. data from some hospitals.

A separate study from Britain, which is not yet peer reviewed, found that people infected with omicron were almost 60% less likely to enter the hospital than those infected with delta.

According to O’Donnell and other experts, the common symptoms of the omicron variant of the coronavirus are fever, fatigue, cough, shortness of breath, and loss of smell and taste. Symptoms also sometimes include congestion, runny nose, diarrhea, nausea, and vomiting.