RALEIGH, N.C. (WNCN) — One of the most important numbers tracked by public health leaders during the COVID-19 pandemic could be on the way out.
And just when it’s looking much better than it did last month.
Department of Health and Human Services Secretary Kody Kinsley said the percent of tests that come back positive — also known as the percent positive, or the positivity rate — is a measure “we may move away from in the coming months,” adding that it’s “not as important to us as other metrics.”
Is he right? Among public health experts, there’s no clear consensus.
“There’s so many variables at this point that it makes the metric a little bit less meaningful,” said Dr. Erica Pettigrew, a family practice physician and assistant professor at the University of North Carolina School of Medicine. “And I agree that we can move away from that a little bit. I think it’s still good to keep our eye on it.”
Dr. Pia MacDonald, an epidemiologist at RTI International, says the percent positive does have value when comparing short-term trends — from one week, or one month, to another — although changes in the overall testing system make longer-term comparisons more difficult.
“The trend and how it goes up and how it goes down still mimics quite closely the number of cases as they rise and fall in our communities,” MacDonald said. “And that’s why that number is still a good indicator of what’s truly going on with the virus locally.”
Health officials have leaned on the percent positive as a way to put the number of new cases in context and to figure out whether enough people are being tested.
That number spiked during the omicron surge in January. On half the days during that month, at least 30 percent of tests confirmed new cases — a rate six times higher than the target rate. It has since fallen closer to 10 percent.
The percent positive depends on lots of people taking tests, with those results being reported to the state database, which calculates the rate at which they are confirming new cases.
But not every test is counted. NCDHHS only uses those PCR tests that are reported electronically directly into the state’s NC COVID database.
A year ago, a CBS 17 analysis found the percent positive had become less reliable because the amount of testing being done across the state had dropped so low that it threw off the numbers.
That wasn’t a problem during the omicron surge: Testing boomed.
The 19 days with the most tests during the entire pandemic took place between Dec. 30 and the end of January.
And at-home tests became more popular, too, with the Biden Administration shipping those rapid tests directly to the homes of people who request them.
NCDHHS reported an average of 16,000 antigen tests per day, by far the highest of any month in the pandemic — and that’s just the ones the agency knows about, because they aren’t always reported to the state and never factor into the percent positive.
“The rise of antigen testing, including at-home testing, makes this metric less reliable,” Kinsley said.
So, what should we watch instead?
Kinsley points to the percent of emergency room visits for COVID-like symptoms — a measure that’s updated every Thursday — along with data from the system that measures the viral level in wastewater across the state.
“Those metrics give us really early indications — along with hospitalizations and, tragically, deaths — to get a more holistic view,” Kinsley said.
And Pettigrew says case counts, both absolute and relative, along with the number of patients in hospitals and the number of deaths — and perhaps more importantly, breaking them down demographically to pinpoint exactly what groups are faring the best and the worst.
“There are more meaningful metrics at this point,” Pettigrew said.