FDA: COVID-19 Rapid Antigen Tests Can Give False Positive Results
NORTH TEXAS (CBSDFW.COM) - Testing for COVID-19 has some caveats.
There are two types of tests that check for infection.
A molecular or PCR test is more expensive and sensitive but takes a day, even up to a week for the results. It is considered a gold standard to COVID-19 test. The second test is more convenient and cheaper. It's called the rapid antigen test which will give results in minutes. Doctors and even the Food and Drug Administration says the results of the rapid test need a closer look.
"The antigen test is like a smoke detector. The smoke detector doesn't look at the fire itself. It just looks at the smoke that comes off of the fire," says Dr. Joseph Chang, chief medical officer at Parkland Hospital System. "The rapid antigen test, looks for bits and pieces of the virus- not the genetic material of the virus," he says
"It can be fooled in either direction. It can not detect virus that's there. But it can also falsely tell you that there is virus when there isn't."
The rapid antigen tests are everywhere. The government sent millions of test kits to schools and nursing homes.
"The FDA only approved the antigen tests in use for people who are symptomatic, that have symptoms. Let's just be clear. It is only cleared for use and approved for use among people who are sick." Dr. Chang says.
"When we use these tests outside of those parameters and test people who are not sick. This is where we run into problems."
He says the antigen test has an accuracy of about 30% for those who have no symptoms.
But there are times where this test can be useful. It can be useful to administer to someone repeatedly and every day. For example sports teams. "they tested their players every single day. Because they don't care if the test is wrong sometimes but if you test every day, eventually they will be right."
Doctors say if you have symptoms, get a rapid test and if you are still negative, check with your doctor or quarantine for 14 days.
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