Arizona expert says rising COVID-19 antibody testing positivity rate normal
Aug 19, 2020, 4:35 AM | Updated: 11:16 am
(AP Photo/Paul Sancya)
(AP Photo/Paul Sancya)
PHOENIX — While the positivity rate for COVID-19 diagnostic testing is trending downward in Arizona, the opposite is occurring for antibody testing. But an infectious disease specialist in Tucson viewed that as normal.
“As we go further into this outbreak, our antibody numbers will continue to climb as they should, because more and more people are adding to that pool that are positive for COVID-19,” said Dr. Sean Elliott, who practices at the Banner University Medical Center.
Antibody testing, also known as serology testing, determines whether a person had the coronavirus at some point in time. Meanwhile, a test to diagnose COVID-19 determines if a person currently has the disease.
The latest state data shows the weekly positivity rate for COVID-19 testing at about 6% and for antibody testing it’s nearing 15%. The diagnostic weekly positive rate peaked at 20% the week of June 28. The antibody positive rate was 7.2% that week.
Elliott said the positivity rate for antibody testing will continue to climb.
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“At some point in time, if we don’t have an effective vaccine for COVID-19, it’s likely that the percentage of antibody tests that are positive in Arizona is going to climb to well over 50%,” he said.
A vaccine being tested in the United States is in its third phase. The company that produced it, Moderna, sought 30,000 volunteers to participate in the trial.
Three research clinics in the Valley and one in Tucson are among the 87 clinics nationwide conducting trials for the vaccine.
Elliott said individuals participating in that trial are perfect candidates for an antibody test. He said researchers want to ensure participants haven’t been infected with COVID-19 before they can get the vaccine.
“It makes no sense to get the vaccine if you’ve already had the infection, because that’ll confuse the results,” he added.
As for who else should get an antibody test, Elliott said he doesn’t recommend “everyone go out and get the test because it really has no meaning in terms of my own personal risk of the disease or being contagious.”
“So the clinical use of the antibody test for a patient is zero,” he added. “That said, it’s incredibly important as an epidemiology tool to understand how many in Arizona have had the infection.”
