More than 10 million Americans have gotten COVID-19 tests in the last week, according to data from the COVID Tracking Project, many of them in order to see family for the Thanksgiving holiday. Experts have urged Americans not to travel this week and have emphasized that a negative COVID-19 test does not mean it’s safe to gather in large groups.
But as lines for tests continue in states nationwide, Yahoo Life sat down with Dr. Dara Kass to help clarify what tests do achieve, which one to choose and when it’s the right time to get one. Kass says there are two types of tests to pay attention to: PCR (polymerase chain reaction) and rapid antigen test, both of which have their own unique way of identifying COVID-19.
Understand the difference between PCR and antigen tests
PCR tests, which can either be a small nasal swab, large swab (called pharyngeal swab) or saliva sample are often referred to as the gold-standard for testing. These tests identify the virus’ genetic material through a process known as reverse transcriptase-polymerase chain reaction, or RT-PCR. “The PCR test will find a smaller piece of virus because of how they look for the virus DNA,” says Kass. “[It] can either be rapid or it can go to a lab can take anywhere from 24 hours to actually up to a week, or even two, to get results.”
Antigen tests, on the other hand, work by locating specific proteins associated with the virus, which means they aren’t as successful in cases where only small amounts of the virus are present. “The antigen test looks for a piece of the virus on the outside and [is] going to come back somewhere around 15 minutes,” says Kass. While this may suggest that antigen tests have less value, Kass says it’s often the right test to choose.
“[Antigen tests] are pretty good at finding people that are contagious. So if you have symptoms of a cold and maybe you think you have a coronavirus, this is a great test,” she says. “In general, for those who are symptomatic, the antigen test is likely the best option since it is quickest and likely to pick up an active infection.”
Don’t get tested right after a COVID-19 exposure
Another important factor to pay attention to, especially for those who believe they were exposed to someone with COVID-19, is the incubation period of the virus. The CDC recommends quarantining for 14 days, which is believed to be the amount of time that the virus can remain dormant in the body. “When you get exposed to the virus, you actually don’t convert to being positive right away,” says Kass. “In fact, most people probably won’t convert until about day three, maybe day five.”
For this reason, she says that testing right after finding out you’ve been exposed is not useful and that quarantining is the only recommended course of action in that case. “If you find out you’re exposed, you should quarantine right away — not to change whether or not you’re going to get infected, but to stop the spread to other people,” says Kass. “And I think that’s really important for people to understand because if you’ve been exposed and you’re going to [become infected], you’re going to have this virus. Nothing is going to stop that, but you can be in charge of stopping the spread to other people.”
Pay attention to what’s happening in your community
In some cases, Kass says that taking tests for the sole purpose of gaining assurance that you’re COVID-19 negative is OK. But if you start to notice an uptick in cases and/or testing delays in your community — and you’re neither symptomatic nor have a possible exposure — maybe think twice about getting one.
“Please be aware of the environment around you,” says Kass. “If you find out that the testing times are taking two, three or four days to return results from a lab, or you see lines that are maybe two, three or four hours long, it’s probably not the best time to take resources away from those who likely need it to make sure that they don't have the virus.”
Be safe over the holidays
Overall, Kass says that “both tests will probably tell you if you’re positive and probably be accurate if you’re negative.” But she emphasizes that the tests are not designed to be used as an indicator of whether it’s safe to move outside your bubble. “A negative test does not clear you to travel; it does not clear to congregate,” she says. “The only reason to test is to find that if you are positive, if you are a negative, it shouldn't change your plans.”
Whether or not most Americans are getting tests for the right reasons, she says that the increase in tests — as long as supplies are available — can still be seen as a good thing. “I’m basically looking at it as a gift to surveillance, that we'll understand a little bit more about where the disease is in our communities because people are taking the initiative to get testing,” she says.
For the latest coronavirus news and updates, follow along at https://news.yahoo.com/coronavirus. According to experts, people over 60 and those who are immunocompromised continue to be the most at risk. If you have questions, please reference the CDC’s and WHO’s resource guides.
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