Testing alone will not keep people safe.
The general test for COVID-19 is a PCR test. A negative result means that the genetic material of the virus was not detected in the sample. For the average person, it takes several days for the virus to replicate often enough to appear in a nose, saliva, or blood sample. Scientists call this a viral load. So if you got a test on Monday but were exposed the previous weekend, you probably won’t show up for the test results.
“This [PCR] test is very good, which is why it is also used so widely. Sensitivity, specificity, and ranges are very good overall, but you know, no test is perfect, ”Rudolph said.
According to the Colorado State Joint Information Center, false negatives of a PCR test are extremely rare. But “false negatives from a rapid antigen test may occur because the test is less sensitive and you may not detect low levels of the virus,” the center said in an email.
Nevertheless, the center said the negative test should not release anyone from quarantine because symptoms of COVID-19 may appear for up to 14 days after exposure.