An announcement this week by The Northeast Texas Public Health District that its daily COVID-19 case counts now include rapid screening results highlights an ongoing disagreement about virus testing.
The regional health authority that has responsibility for reporting Gregg County virus numbers said in a statement that since COVID-19 arrived in East Texas, the organization's notices of new cases had included only positive lab results from a "PCR Test, or a Polymerase Chain Reaction Test."
"The PCR Test requires a certified testing laboratory to physically receive collected samples and to perform analysis that may take several hours or a few days before results can be confirmed," NET Health said in the statement. "In August 2020, the Texas Department of State Health Services (DSHS) requested all public health departments to also include reports of all positive antigen results, also known as the rapid test, within local reports of all PCR-positive statistics."
Now, PCR-positive results and antigen-positive results are combined into NET Health's reports of new daily cases.
This week, Gregg County Health Authority Dr. Lewis Browne said Christus Good Shepherd has been performing the antigen, or rapid result testing, despite the fact that the "gold standard" of testing is the PCR testing. He said that the antigen testing results in "skewed" data.
"When you're trying to follow this, you need to the real stuff," he said, adding that Christus invested heavily in developing its own antibody tests.
"Antibody testing is not very good testing," he said, and added that this particular kind of screening doesn't react like other antibody tests by showing first if someone has an acute infection and then immunity from past infection.
Christus isn't the only local facility using antigen testing, said Terrence Ates, spokesman for NET Health.
"There are some local community clinics, urgent care facilities, and independent doctor's offices that have the necessary equipment to provide rapid test results to clients, and positive rapid tests are recognized by DSHS as being a positive probable case," he said.
Dr. Andria Cardinalli-Stein, ambulatory chief quality officer for Christus Trinity Clinic, and Dr. Faber White, chief medical officer for Christus Good Shepherd Health System, said several antigen, or rapid, COVID-19 tests have received emergency use authorization from the Food and Drug Administration.
"These antigen tests can be performed in a clinic setting or emergency department, and results are available within a matter of minutes. PCR testing turnaround typically still takes several days, which is a major advantage of the antigen test," according to a statement from Cardinalli-Stein and White. "All of these antigen tests have an excellent specificity in confirming that a patient has COVID-19. The likelihood of someone receiving a false positive result is incredibly small, essentially the same as a PCR test. This means that if a patient has a positive antigen test, it is highly reliable and confirms they have COVID-19, with an extremely small margin of error.
"Different antigen tests do vary in their sensitivity, which is the likelihood of a negative test result indicating the patient truly does not have COVID-19; an error would indicate a 'false negative.' Each of the antigen test manufacturers have thoroughly studied their product and given physicians across the country recommendations regarding the test’s sensitivity in detecting the illness at various stages. The Sofia antigen test in use at Christus Trinity Clinic and Emergency Department locations in Longview provides the highest sensitivity within five days of symptom onset; within this time frame, the sensitivity approaches that of the PCR test."
However, it's still possible a patient at Christus would receive a PCR test, as well.
"At Christus, if a patient presents having experienced more than five days of symptoms, the provider may still initially order an antigen test, because if it is positive, it is still meaningful and gives rapid results, but if it is negative, a PCR test is always ordered to ensure an accurate diagnosis," the hospital representatives said. "After more than five days of symptoms, the sensitivity of the antigen test begins to wane. However, even after five days of symptoms, the antigen test retains its high specificity; a positive antigen test confirms that a patient truly has COVID-19, just like a PCR test does."