Antigen tests, on the other hand, are a fraction of the cost, currently ranging from $25 to $50.
What should you check for on the box?
Make sure the home test or collection kit you’re looking to buy has an emergency use authorization from the F.D.A. (it will be printed on the box) and that the company works with certified lab partners. Also look for tests that offer a telemedicine consult, advised Dr. Cruz, so you can discuss your diagnosis and next steps.
How should I interpret a result from an at-home coronavirus test?
Following the test kit instructions is key to getting a reliable result. “A specimen that is not collected correctly may lead to false negative test results,” said Dr. Cruz. Imperfect swabbing technique, or swabbing only one nostril, may increase the risk of less accurate results. And samples for test-by-mail kits should be shipped the same day they are collected; the less time in transit, the better. Samples sent on weekends or holidays may be delayed, though some use FedEx and overnight shipping.
If you test positive on either a mail-in P.C.R. or at-home antigen test, you are likely to be infected and presumed contagious, said Dr. Bacci, so isolate from others and continue to monitor your symptoms. Repeat testing can help track the disease course, if, say, someone goes from being asymptomatic to displaying symptoms.
Negative results are more likely to be wrong than positive ones. “A negative result does not necessarily mean you do not have Covid, which is the same interpretation for either an at-home test, a mail-in test or one offered in a doctor’s office,” said Dr. Cruz. Continue to wear masks, socially distance and practice good hygiene, especially if you have symptoms or known contacts with others with Covid.
When would a test be inappropriate to use?
Dr. Gronvall is concerned that some people are using at-home tests after they’ve been vaccinated to make sure that the vaccine has worked. But neither the P.C.R. or antigen-based tests will be able to discern whether the vaccines have built up immunity in your body.
That’s because the vaccines encode for snippets of the virus and not the entire sequence. The P.C.R. and antigen tests search for a different portion of the virus from what’s included in the vaccines.
“These tests are not going to tell people if the vaccine is effective,” she said.
What does the future of at-home testing look like?
Beyond saliva and nasal swabs, some scientists are looking to develop devices that look like breathalyzers to detect chemicals in an individual’s breath that correspond to coronavirus infection. “We’re looking for the body’s response to infection and disease,” said Pelagia-Iren Gouma, a materials engineer at The Ohio State University.