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PCR and antigen tests for COVID-19: Need to know

COVID-19 tests are in high demand, but with so many options, it can be hard to know which one to get.

CALIFORNIA, USA — All across California, people will find long lines at testing sites as the omicron variant continues to surge. 

Nearly two years into the pandemic, there are more tools to fight against the virus including vaccines, as well as PCR and antigen tests. Dr. Phoung Luu, public health officer for both Sutter and Yuba counties, says the PCR tests are more accurate than a rapid antigen test when it comes to identifying infections and says false negatives are very rare.

"The only challenge with them is that they can also detect non-viable or dead viral particles, so that's why they last up until 90 days turning positive," she said. 

She says, if you test positive with a PCR test and want to see if you're still positive after five days, then using a rapid antigen test will be your best bet.

"And the reason why is that the rapid antigen test doesn't detect that dead component of the viral particle, the non-viable component. It really just detects if the virus is still alive," she said. 

As far as cons, turnaround times for PCR test results could take anywhere from two to five days right now because of the high demand. 

When it comes to rapid antigen tests, the pro is that results come in 15 to 30 minutes, but for those administering the test at home, accuracy of the results depends on the user. Things like how much to swab and how many drops to use for specific brands can play a factor.

"Always make sure to read the directions within the box before you start opening the kit and before you start testing," Dr. Luu said. 

With the spike in cases, she also recommends upgrading from a cloth mask to a K95 or K94 mask or at least a well fitting surgical mask.

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