Covid rapid home tests: How accurate are they and other questions answered


If you’re using a rapid test to reduce the risk of a holiday gathering, be sure to take it the day of the event, preferably about 15 minutes before you walk out the door. Recently, a Christmas party in Norway became a very popular event even though everyone was vaccinated and used a rapid test. But in this case, people tested a day before the event.

Two tests are better than one. The biggest mistake people make using rapid home tests is taking one test and thinking it means they don’t have Covid-19. If you are concerned that you have been exposed to Covid, you must take at least two tests over a period of three to four days. The Centers for Disease Control and Prevention says the best window for testing after potential exposure is to test three to five days after the high-risk event or contact with an infected person.

The bottom line is, the more often you use the tests, the better, said Dr Michael Mina, a former Harvard epidemiologist who is now the scientific director of eMed, a company that checks test results at home. If you want to spend time with a medically vulnerable person, you should be tested a few days before seeing them and then retested on the day of the visit.

“Think, how can I test as close to the thing I’m doing as possible?” said Dr. Mina. “When I go to visit my parents, I always bring rapid tests with me. Right before I walk through the door, I use the test in my car.

Most of the time, a positive result means you have the coronavirus, especially if you have symptoms. But false positives happen. Recently, Ellume, an Australian company, recalled almost 200,000 test kits due to concerns about a higher than expected false positive rate.

If there is reason to doubt a positive result, do another test, preferably from another manufacturer or at a test center. People hosting large events, such as weddings, who use the tests to screen guests should have a few extra tests of a different brand on hand for guests who test positive. You can be sure of the result if the second test is negative, Dr Mina said.

“It would be really rare for someone to have a true positive and then have a second test show a false negative result,” he said. “If you’re having dinner, you might as well cancel dinner if someone tests positive. But if it’s a high-consequence event, like you get married and fly somewhere, and you’re going to screen a few hundred people, you may get a false positive and want to test again.


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