![]() ![]() ![]() That makes rapid tests much more likely to confirm or deny your infection: The more of a "viral load" you have, the more likely a rapid test is to catch it.Ĭrawford agrees: "hat is when the 'viral load' is highest, and is what the tests were originally approved for by the FDA. If you have Covid, you'll be "the most contagious" when you're first experiencing symptoms, Gronvall says. "Rapid antigen tests are excellent tools to tell people if they are currently infectious and should isolate," Gronvall says. If you're asymptomatic, but concerned about potential exposure to the virus, take a PCR test. The short answer: If you think you're experiencing Covid symptoms, take a rapid antigen test. ![]() When should you take an at-home test instead of a PCR test? James Crawford, senior vice president of Laboratory Services at Northwell Health and professor at the Feinstein Institutes for Medical Research.Īt-home tests may also be significantly more accurate in kids: According to a preprint study led by Johns Hopkins researchers, published earlier this month, rapid antigen tests and PCR tests have similar accuracy levels for children. Their convenience particularly makes them a key part of the "national strategy for reducing the spread of this virus," says Dr. So while at-home tests aren't 100% effective, they still have their place. The downside is that they take time: Results can only be gathered in a laboratory setting, meaning even the quickest turnarounds can still take at least 24 to 48 hours. They can tell if you're currently infected, or if virus fragments are hanging around in your system after you're no longer infected. PCR tests detect genetic material or fragments from specific organisms or viruses, such as Covid-19. That means at-home tests miss roughly 15% of positive cases, which can sound like a high figure, especially when millions of people get tested each day.īut rapid tests aren't far behind the accuracy levels of polymerase chain reaction (PCR) tests, which are "considered to be the gold standard" in Covid testing, says Gigi Kwik Gronvall, a senior scholar at the Johns Hopkins Center for Health Security. Results typically take about 15 minutes.Īccording to the Centers for Disease Control and Prevention, at-home antigen tests like BinaxNow are roughly 85% accurate at detecting positive cases. They require users to rub a nasal swab inside their nostrils a few times on each side, and then expose the swab to a few drops of chemicals. At-home tests detect small viral proteins called antigens. ![]()
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