A closer look at the at-home tests for COVID-19

Emily Anthes

In the early months of the pandemic, getting a corona- virus test typically required visiting a health care center, a laboratory or a dedicated testing site, a process that sometimes involved long lines and waiting a week or more to get the results.

Americans can now take rapid virus tests from the comfort of their own homes. Many of these tests are avail- able without a prescription and return results in just 15 minutes.

Although rapid tests have their limitations, they are an important public health tool, experts said, particularly if you know how to use them.

“Having that information and being able to make bet- ter decisions is very powerful,” said Mara Aspinall, an expert in biomedical diag- nostics at Arizona Stateuniversity who is also on the board of directors of OraSure, which makes rapid COVID tests. “And the abil- ity to do this on a while-you- wait basis is something that we couldn’t do a year ago.”

What kinds of tests are available?

A handful of rapid at-home tests are available without a prescription, including the Abbott Binaxnow, the Ellume COVID-19 Home Test and the Quidel Quickvue At-home COVID-19 Test. Prices range from about $10 to $40 per test, though President Joe Biden has announced plans to reduce prices by roughly one-third.

All three detect small viral proteins, called antigens. The tests require rubbing a shal- low nasal swab inside your nostrils and then exposing the swab to a few drops of chemicals. They provide results in about 15 minutes.

The tests themselves are fairly straightforward, but each one involves a slightly different procedure, which should be followed to the letter, experts say.

How accurate are rapid antigen tests?

Rapid antigen tests are less sensitive than the ones done at a testing site. If you take one during the earliest phase of an infection, before the virus has replicated widely, the test could return a false negative.

Some of the at-home antigen tests have an overall sensitivity of roughly 85%, which means they are catching roughly 85% of people who are infected and missing 15%. In some studies, their real-world performance has been even lower.

But the testsare more sensitive in people with symptoms than without and are most sensitive during the first week of symptoms, studies have found. And antigen tests are excellent at flagging people who have high viral loads — and who are thus most likely to be actively transmitting the virus.

When and how should I use them?

Rapid at-home tests are a good option for people who have been exposed, who want to know whether a sore throat is COVID-19 or just a cold, or who want a little bit of extra assurance.

People with symptoms can take a rapid antigen test immediately, experts said, but those who have had a known exposure to the virus should wait three to five days before doing so.