Rapid antigen tests are the cheapest (approximately $ 12 per test) and are available in retail stores and online. (They are usually not covered by insurance.) Abbott’s BinaxNOW test includes two rapid antigen tests per pack and costs about $ 24. To take the test, simply wave the swab in both nostrils and place it in a special card. After 15 minutes, the result reads similar to a pregnancy test: Two pink lines indicate that you are positive for Covid-19. The QuickVue At-Home test from Quidel is similarly expensive. After wiping your nose, soak the swab in a solution in a test tube and then in a test strip. You will get results in about 10 minutes.
June 29, 2021, 7:34 a.m. ET
The rapid antigen tests are less reliable for finding Covid-19 in people with low viral loads than the “gold standard” PCR tests you can get from a healthcare provider. One study found that a rapid home antigen test had a 64 percent chance of correctly detecting the virus in people with symptoms who tested positive on a PCR test. (The test only caught about 36 percent of those who had the virus but had no symptoms.)
But don’t let these numbers put you off. The inexpensive rapid antigen tests provide a reliable rapid test to identify people with infectious virus levels. Suppose you want to invite unvaccinated friends or children to your home. Before hosting an indoor event, you can reduce the risk of asymptomatic spread and infection by 90 percent or more if all guests have a rapid antigen test within an hour of the event, said Dr. Mina.
Rapid tests can also be used as extra protection before spending time with people who are at high risk of complications from Covid-19, such as immune problems or cancer treatments. Neeraj Sood, professor and vice dean of research at the University of Southern California and director of the COVID initiative at the USC Schaeffer Center, said that despite being vaccinated, he would do rapid tests to take extra precautions around such people.
“If I was hanging out in a closed room with a friend who was on chemotherapy and didn’t get the vaccine, I would do two tests,” said Dr. Sood. He did a rapid antigen test three or four days before visiting his friend and another test on the same day of the visit. “If both are negative I am very confident that I don’t have any Covid and I will not pass it on to my friend,” he said.
Rapid tests could also be used to make a small family reunion at home or a children’s birthday party with a mix of vaccinated and unvaccinated people safer. “When you put that extra layer of home testing in place, you are all more confident,” said Irene Peterson, professor of epidemiology and health informatics at University College London. “Or you could choose not to have the party.”
If you want more certainty than a rapid antigen test can provide, consider a more expensive, rapid molecular test to use at home. These tests work by detecting the actual genetic material (RNA) of the virus and amplifying it to see if you are infected. A home-use rapid molecular test works almost as well as the PCR tests done in test centers that are processed by a laboratory, but they are also more expensive than the home antigen tests. Lucira does a high-accuracy molecular test for $ 55 that uses nasal swabs and a battery-powered processing unit that gives results in 30 minutes.