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Some counties have had delays reporting negative results, typically one to three days. But we don’t yet know how widespread that is or was.
Dane County saw the longest delays, up to 10 days. But after a reporting change July 24, 2020, they now report all negative results as soon as they’re known.
Outside Dane County, these delays wouldn’t have had much effect on the more trusted seven and 14-day rolling averages of how many tests were positive.
And percent positive is just one of several key indicators that guide local decision-making — the others weren’t affected by the backlogs.
A growing list of Wisconsin communities are mandating mask use in public amid rising COVID-19 case counts.
Debate over those decisions has increasingly split on party lines, with Democrats generally favoring masks and other broad measures while many Republicans favor fewer or no limitations. The sides have consistently sparred over what is a reasonable response to the latest trends in the pandemic.
But are these politicians and decision-makers relying on bad data?
That was the claim from state Sen. Steve Nass, R-Whitewater, in a recent appearance on a conservative radio show.
"Local governments are making these (COVID-19) decisions on inaccurate data because the negatives are not being entered," Nass told host Vicki McKenna in a July 24, 2020, interview on Madison’s WIBA. "They’re sitting on these things across the state of Wisconsin."
The longtime lawmaker took aim at Dane County in particular, asserting 17,000 negative COVID-19 tests "have not been reported" by Public Health Madison & Dane County, which when factored in lowered the occurrence of positive tests to 2.1%. That would be drastically below the statewide average of around 10% and the 5.5% figure Dane County had most recently reported for a two-week average.
Nass then went a step farther to claim the tests were delayed intentionally.
"This is all about fear and scare: We want a mask mandate, we’re going to get it one way or another," he said. "Dane County I believe purposely held back these negatives long enough so they could get their mask mandate and they can restrict restaurants and bars even more."
Nass made similar points in a later news release, saying the backlog "dramatically skews" daily and longer-term averages. He called on health officials to publicly announce if they have or had backlogs since June.
For this check we’ll set aside Nass’s claims about Dane County’s motivations and focus in on his initial claim:
Is he right that negative tests aren’t being reported across the state, skewing data used by decision-makers?
We’ll start with the claim of missing tests. There have, indeed, been delays reporting negative test results.
The day before Nass’s interview, state Health Services Secretary Andrea Palm acknowledged to the Milwaukee Journal Sentinel that health departments around the state were behind in processing and reporting negative tests. She said the delays were generally one to three days, but Dane County officials were about 10 days behind at that point.
Palm said that certainly impacted the percent positive stats on a "day-to-day basis" and encouraged the public to rely on the seven-day average for a more accurate picture. Health officials have consistently pointed to longer-term averages like this, since one-day tallies for positive cases and percent positive can jump up and down for a variety of reasons.
The state Department of Health and Human Services did not say how many health departments had such backlogs. That question remained unanswered as of July 29, 2020, though a department spokesman said then it was less than half.
To better understand why this happens, let’s zoom in on Dane County, where Nass focused his comments.
People who take tests are notified as soon as results are available — whether results are positive or negative. But those two groups were not reported in the same way, Public Health Madison & Dane County said in a news release and Facebook post.
All tests must be manually verified to ensure the person taking the test lives in Dane County and that other information like the address is properly filled out. This happens immediately on positive tests, for which officials must conduct contact tracing. Positive tests are then immediately added to the tallies reported to the state health department and on the Dane County COVID-19 dashboard.
But this manual verification caused a backlog among negative tests as testing volume increased. Dane County didn’t report those numbers until the locations were verified, which was taking as long as 10 days. So while long-term averages were in the ballpark, daily counts could be significantly skewed.
Other health departments had similar delays while the negative test results were in what officials call a "staging area" awaiting verification, but delays elsewhere weren’t as long.
On July 24, Dane County changed its methodology and began reporting negative test results as soon as results were available. They now adjust those tallies down later to account for tests from people who live outside Dane County — typically about one-third of the tests.
Through July 28, the health department said 19% of the tests it processed had been for people with addresses outside Dane County, and another 15% were missing addresses.
This change resulted in 17,000 negative tests being added to the dashboard on July 24 — the number referenced by Nass. The health department said the seven-day average at that point was 2.1%.
But the county had acknowledged a delay in negative tests starting almost a month earlier. The weekly data releases starting June 29, 2020, said the backlog was affecting the reported numbers. And as the backlog grew, the weekly release for July 20 didn’t even include a percent positive calculation.
But those data releases from June 29 to July 20 didn’t explicitly state the delay was wrongly inflating the percent positive tallies. And it was affecting the tallies.
For example, the July 13 update listed the percent of positive cases over the preceding two weeks at 5.5%, above the targeted threshold of 5%. But the updated data released July 24 showed the actual two week-average at that point was 3.8%, once all negative tests were factored in.
This brings us back to Nass’s fundamental claim — that this skewed data is especially problematic because it is being used by local decision-makers.
Wisconsin has not implemented any statewide mask requirement, though the majority of states have one at this point. So the state has a patchwork of local government-imposed mask mandates, including from Milwaukee and Madison.
The percentage of COVID-19 tests with a positive result has been a key indicator of virus prevalence, but Nass’s assumption that the negative test delays skewed local decisions has a couple of problems.
First, the delays outside of Dane County have been described as limited to a few days at most. That will affect daily counts, but not the seven- or 14-day averages that health officials have long pointed to as more reliable indicators. And that’s just one of many indicators that could factor into decision-making, along with the number of positive tests, hospitalizations and deaths.
Second, this assumes decision-makers wouldn’t be aware of the negative test backlog. We don’t know all of the counties that have a backlog, so we can’t trace decision-making processes everywhere. But we know in Dane County this logic doesn’t hold water. The restrictions put in place there the first week of July came from the health department, which was of course aware of its own backlog of negative tests. It even referenced the delay publicly before that point.
A blog post from the health department July 27 said the negative test backlog did not alter the decision to add restrictions.
"To be clear, percent positivity is just one metric we monitor and was not the reason for the new orders that were issued in July," the post said.
The release went on to note that Dane County had posted its highest seven-day totals for positive tests in the week before the new restrictions on July 2, and again in the week before the mandatory mask order July 7. It said metrics on lab timeliness, contact tracing and community spread were also red at that point.
It’s important to note, however, that mask mandates in other places around the state have been imposed by county boards and city councils, who would not have such intimate knowledge of testing data. But it seems reasonable to presume such decisions would typically be made in consultation with local health officials, who would know that data.
Nass said local governments across the state are making decisions based on inaccurate COVID-19 data "because the negatives are not being entered."
Nass is right that a delay reporting negative tests led to the release of inaccurate data, which local decision-makers could have partially relied on while deciding to implement additional restrictions. But his description overreaches on several fronts.
The backlogs outside Dane County were generally just a couple of days, so they wouldn’t have much effect on the more trusted seven and 14-day rolling averages of how many tests were positive. And percent positive is just one of several key indicators that guide local decision-making — the others weren’t affected by the backlog.
For the longer backlog in Dane County, it makes no sense to claim local decision-makers were unaware of the 10-day backup, since the orders came from the health department itself.
Factoring in those elements, we have a statement that is partially accurate but leaves out important details. That’s our definition of Half True.
Steve Nass, appearance on Vicki McKenna radio show, July 24, 2020
Milwaukee Journal Sentinel, County health departments behind in processing negative tests, affecting daily COVID-19 data, July 23, 2020
Email exchange with Steve Nass, July 27, 2020
Steve Nass, news release, July 27, 2020
Public Health Madison & Dane County, Facebook post, July 24, 2020
Public Health Madison & Dane County, news release, July 27, 2020
Public Health Madison & Dane County, COVID-19 dashboard, accessed July 27, 2020
Email exchange with Public Health Madison & Dane County, July 27-28, 2020
Public Health Madison & Dane County, data snapshot, June 29, 2020
Public Health Madison & Dane County, data snapshot, July 6, 2020
Public Health Madison & Dane County, data snapshot, July 13, 2020
Public Health Madison & Dane County, data snapshot, July 20, 2020
Public Health Madison & Dane County, mask mandate order, July 7, 2020
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