Coronavirus tracking metrics used by regional health officials to levy social restrictions were flawed throughout July because of delays in test processing, according to data analysis and interviews by the Post Register.

The flaws mean the number of active cases tends to be understated.

In late July, test results took about 10 days to come back, Eastern Idaho Public Health said. That delay has since decreased, but the test turnaround delays last month resulted in incomplete daily information, which left regional health officials to rely on old metrics to decide on coronavirus response measures.

Delays in testing and other “errors” with coronavirus data can “build up, and pretty soon, you’re on a runaway train, and you’re not getting to your trigger points (to decide on new social restrictions) as rapidly as you need to to avoid overwhelming your health care system,” University of Idaho professor Benjamin Ridenhour told the Post Register. He designed the COVID-19 model used by the state of Idaho.

Eastern Idaho Public Health officials actively monitor coronavirus cases from the time they get the test results back from the state lab until the person has been asymptomatic for 10 days. By the time coronavirus cases have been publicly reported by the health district recently, most people hit that benchmark within a few days. That time between the case being publicly reported and the person recovering enough to be released from monitoring narrowed throughout the month of July, the Post Register found.

During the first week of July, the average patient in eastern Idaho was monitored for nearly a full week by public health officials after testing positive for the virus. That dropped to just four days of monitoring during the last week of July. That means a person who tests positive for COVID-19 is counted as an active case for a shorter time period.

Some cases are listed as recovered, or released from the health district’s monitoring, the same day they are first reported. Of the 297 cases reported during the last week of July, more than a quarter were immediately released from monitoring after the health district reported the case.

The health district’s regional coronavirus response plan focuses on active case counts sustained for three days, along with hospitalization metrics, to determine what social restrictions to pursue.

Two people who study the coronavirus in Idaho told the Post Register that with significant delays in testing and case reporting, daily case counts don’t provide a real-time picture of how widespread the virus is locally.

“I don’t put much stock into the daily case reports,” Ridenhour said. “Over time and as the dust settles and you look back at the data a bit, then I” start trusting it.

Testing delays complicate responses

James Corbett, community health administrator with Eastern Idaho Public Health, said active case rates account for two concerns with tracking COVID-19 cases: Making sure mitigation strategies are based on current cases and accounting for the delays in symptom onset.

“If we receive a report that someone was sick 20 days ago, that’s really not demonstrating or reliably stating what’s happening right now,” he said. “So, we’re trying to be as closely aligned as we can get.”

But some who track the coronavirus say that active cases can only catch blips of cases for a few days when testing is delayed and limited. Ridenhour said people who use active case rates must account for testing delays in their models.

For example, health officials could zoom out and look to weekly averages of new cases, as many national coronavirus trackers are doing.

Dr. Ronald Solbrig, who serves on Idaho State University’s coronavirus task force, said concerns about data reliability make already difficult decisions about coronavirus response measures even more onerous. On one hand, hospitalization data is “clearly an indicator when things are really, really bad” because the medical system could become overwhelmed, Solbrig said.

Ridenhour said he looks to hospitalization data to create projections for how widespread coronavirus will be in four weeks. The data is somewhat less current, he said, but it’s more complete.

“It’s a bigger delay, but the tradeoff is that you can maybe ... have a better forecast using those data than using the case rates because of the consistency of those data,” Ridenhour said.

More immediate data, like case reports, can better capture how severe the pandemic is. Both Ridenhour and Solbrig said reported cases are only a reliable metric if testing is truly random. In most places, testing is dependent on who seeks tests and how severe their symptoms are.

“If testing is bad,” Solbrig said, “then we have no confidence that we know what’s happening in our community.”

Skewed counts

The daily active case rate fluctuates rapidly with eastern Idaho’s small population. It doesn’t take many cases to change the designation for some smaller counties.

Clark County’s population of less than 1,000 is so small that the health district chose to handle restrictions on a case-by-case basis. Larger counties like Jefferson have, in recent weeks, constantly teetered between being above or below the 10 active cases per 10,000 residents threshold that would put them in moderate risk, where the board’s plan calls for mask mandates and large event bans.

Eastern Idaho had mostly escaped major outbreaks of the coronavirus until near the end of June. As the number of cases and tests grew, the region encountered the same backlog for test results that had affected Idaho when the virus first arrived in the spring.

Express Lab, which provides private coronavirus tests and has worked with Mountain View Hospital on drive-through testing, saw a backlog of nearly 14 days for test results around the Fourth of July. Lab manager Lori Leask said turnaround time has since come down to around three days.

“I will say, that can change any day when you see spikes in demand. It overloads the system, and it pushes them all back for a few more days,” Leask said.

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