ST. GEORGE — The Utah Department of Health is pausing the use of rapid COVID-19 tests at many of its free testing sites in the state, including the drive-thru site at Tech Ridge in St. George, after it was determined they were unsuccessful at finding the presence of COVID-19 at least 62% of the time.
The tests were also scheduled to be used at the Cedar Fun Center in Cedar City. However, the particular rapid tests, manufactured by GenBody, had not been used yet at the Cedar City site and had just been delivered to the testing site in Cedar City and others run by TourHealth, said Utah Department of Health Executive Director Nate Checketts.
Starting Monday, the TestUtah site at Tech Ridge and the TourHealth site in Cedar City will only offer the more thorough PCR swab test, which has to be sent to a lab, usually up north in Salt Lake City. Because of that, results don’t usually come for at least 24 hours, or as many as 72 hours. That compares to the 15 to 30 minutes it takes to get a result from a rapid test.
The health department said an at-home rapid test from a different manufacturer will also be provided at request to those who take the PCR test for those needing a quicker result.
It is unclear if the issue with the rapid tests is limited only to the antigen tests manufactured by GenBody or extend to rapid tests made by other manufacturers. However, the Utah Department of Health said it also studied results from another rapid test used at the test centers manufactured by BinaxNow and found they showed better results.
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However, Checketts said because of a nationwide shortage, access to BinaxNow tests are limited in Utah. He added the pause of rapid tests at state-run sites will likely last for a “few weeks” as the department does further analysis.
Concerns were raised last week after health department epidemiologists analyzed the results of 18,000 Utah residents who had received both the GenBody rapid antigen test and a PCR test. Of the 100 who were confirmed positive by the PCR test, 62 came up with a false negative in the rapid test.
“There were likely positive cases we missed,” Michelle Hofmann, deputy director of the Utah Department of Health, said during a Zoom press conference Sunday afternoon. However, as has been the case in the past, she added the idea of a positive COVID test being false is not probable.
“What we were seeing were false negatives not false positives,” Hofmann said. “If you got tested positive, you had COVID-19.”
The state epidemiologist, Dr. Leisha Nolen, noted that while the data was discovered last week, the tests that formed the data came from tests conducted in December before the surge of the omicron variant. That means the faulty tests don’t have to do as much with an inability to test for omicron, which in just weeks has completely usurped delta as being the source of more than 90% of COVID-19 infections.
“It was the delta variant so not specific to omicron,” Nolen said. “It was actually a little better at detecting omicron.”
Besides a greater ability to infect people than other variants and less ability to cause severe infections, something else that has separated omicron from delta or other COVID-19 has been how quickly omicron recedes after coming in like a hurricane. That receding has been in full evidence in Southern Utah in the last week, though the hospitalizations and deaths in omicron’s wake are still being dealt with.
Regardless, Hofmann said if someone tested negative for COVID-19 in the last five days at the Tech Ridge site using a rapid test, they should go get retested. She also said the previous guidance by the state to not get tested if you have the symptoms of COVID-19 and just assume you have it still stands.
That also applies if a person has a negative test and feels like they actually have COVID-19.
“If you test negative and still have symptoms of COVID… you should still assume you have COVID and isolate for 5 days,” Hofmann said.
Differences between tests
Officials had previously informed the public that the rapid antigen test is not as accurate as the PCR lab test and should be used more as a screen to keep those with COVID-19 from being out where they can infect others. But the number of false negatives found recently was concern enough for a pause.
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“We did know the rapid tests were not as sensitive,” Nolen said. “PCR tests are the gold standard.”
According to the Centers for Disease Control, the rapid antigen test has a 21.7% chance of a person with COVID-19 testing negative, the chance for a false negative is 2.8% with the PCR test.
According to the CDC, a rapid antigen test looks for an antibody reaction to COVID-19 in the body, while a PCR test goes deeper and looks specifically for the genetic material of COVID-19.
The rapid test treats a sample with a liquid that is a combination of salt and soap that breaks apart cells. This liquid is put on a test strip with COVID-19 antibodies. If COVID-19 is present, those antibodies turn red and show up as a straight line.
The PCR test uses what is called a polymerase chain reaction that has to be done in a lab and can find DNA from SARS-CoV-2, the virus that causes COVID-19.
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