Lab backup forces one local county to change COVID-19 test method
WACO, Texas (KWTX) - A lab backup has forced the Waco-McLennan County Health District to use a faster, but less accurate test for the new coronavirus.
Two, the polymerase chain reaction or PCR and antigen tests, show whether a person is infected with the virus, while the third, antibody or serology testing, shows whether a person had an infection in the past.
"The best test is the one we have used since the beginning, that being the PCR test," Waco Family Health Center CEO Dr. Jackson Griggs said.
Griggs says he used the PCR test up until one week ago when there was a backup at one of the labs the county used.
"We recently had to pivot to antigen testing instead of PCR because of a temporary stop in labs we use in Austin," Griggs said.
Antigens are molecules that can stimulate an immune response, while an antibody is a large protein the immune system uses to neutralize such pathogens as bacteria and viruses.
Griggs says the antigen isn't as accurate as the PCR, but is still approved for use.
“Those tests do have a false negative rate that we don’t love; it’s about 80% accurate,” he said.
While the tests might not be as accurate they do provide results faster.
“On the flip side we run those antigen tests in house, so we get the results back same day,” he said.
This is a similar story when it comes to rapid testing, which is performed in small samples by the county's Abbott Now machine.
"We have had an Abbot Now instrument for a few weeks, but we have been very selective about using it."
Griggs again says with this test there is a speed versus accuracy issue.
"With that test you have to weigh getting the results back fairly quickly, but you end up with a little bit higher false-negative rate."
Griggs hopes that labs get back to full speed so they can eventually switch back to PCR tests in the near future, but he says that will only happen if people do their part to slow the spread.
“You wearing a mask isn’t about you,” says Griggs.
“It’s about protecting your brother, sister, mother, father and your grandparents,” he said.
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