EVANSVILLE, Ind. — Vanderburgh County saw a stunning turnaround last week, registering the lowest daily number of COVID-19 cases in months on one day and on the next, the highest number yet.

What happened?

The answer likely has a lot more to do with far-flung private laboratories and the speed at which they can process large numbers of tests than any sudden new explosion of COVID-19 cases locally.

But then, some of the local COVID-19 testing numbers appear as hard to fathom as the work of the laboratory technicians themselves, pointing up when logic would suggest they point down.

The issue burst into the open with Wednesday’s news that Vanderburgh County added just seven new cases of COVID-19, the lowest number in months. It was right there on the Indiana State Department of Health’s daily dashboard tracking cases statewide. The next day’s news also was a stunner. This time, the county rang up a record 63 new cases. And on Friday, 56.

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Wednesday’s low number could be explained, in part, by the fact that Vanderburgh County also reported just 205 newly administered tests. Thursday’s comparatively large haul of 63 new positive test results came against 592 new tests. The wave crested Friday with Vanderburgh County reporting an eye-opening 993 newly administered tests.

A wave of new test results rolled in Friday

It’s all part of a late and large wave of unreported negative test results rolling in to be tacked onto the ISDH dashboard, State Health Commissioner Dr. Kristina Box told reporters last week.

Private laboratories process test results to be included on ISDH’s dashboard, Box said, but they often send their positive results first, leaving a skewed picture of COVID-19’s spread until they send in their negative results. Positivity rates consequently look higher than they really are.

“We have some labs that will report to us on a Tuesday, or they’ll report on a Tuesday-Friday, something like that,” Box said. “So the more that we can get those negative tests in on a regular basis – the positives we always get in. They’re very good about reporting those very timely, because they know we want to contact trace those.

“And we are constantly onboarding more labs.”

Friday’s massive wave of new test results was reflected statewide, not just in Vanderburgh County. ISDH reported 11,613 newly administered tests on Thursday. Friday’s number, 34,323, was nearly three times as high.

On Friday, the ISDH dashboard displayed a message that illustrated the growth in testing options — and the impact it can have.

“An additional testing facility has been newly onboarded into the electronic reporting system,” it stated. “This onboarding resulted in the addition of 279 cases, 9,434 tested individuals, and 15,814 tests administered to today’s counts.”

Simple timing also should be baked into any understanding of ISDH’s numbers, which reflect when the state agency receives and confirms the report of a test as positive — not when the sample for the test was taken.

“New positive cases, deaths and tests have occurred over a range of dates but were reported to ISDH in the last 24 hours,” the dashboard states.

Positive test numbers have been all over the lot

Vanderburgh County’s positivity rate — the percentage of people tested who come up positive for COVID-19 — did go down with Friday’s massive load of presumably negative test results.

The county’s 7-day positivity rate for unique individuals, a number thought to be indicative of what’s happening on the ground, dropped to 6.4% from Thursday’s 6.8%.

But the total haul of positive test results has been all over the lot. While newly administered tests in Vanderburgh County nearly tripled — from 205 on Wednesday to 592 on Thursday — Thursday’s 63 positive test results was nine times Wednesday’s number.

Friday’s 56 positive test results were seven fewer than Thursday’s 63 — but the number of newly administered tests was nearly twice as high.

‘We see this wax and wane’

Deaconess Health System announced in April that newly-purchased testing equipment meant it no longer had to send test samples to out-of-town private laboratories and await those results.

But Deaconess still sends out some 20 percent of its testing to private laboratories, the hospital system said. It is now pointing to October to finish the job.

“We do all of our (emergency department) and inpatient testing for our organization and affiliates on-site,” Dr. April Abbott, director of microbiology at Deaconess, said in an email. “In October, our testing capacity should increase, and our hope is to be able to do all testing here at Deaconess.”

Yes, Deaconess has seen an increase in testing at its sites, said Deaconess Laboratory Director Phil Gamble.

“This increased demand for testing is likely attributed to a combination of an uptick in overall prevalence and in schools opening,” Gamble said by email.

Box pounded home the point: Numbers can be skewed by the speed, or lack thereof, of test processing. No single number tells the whole story, the state health commissioner said, noting the delays in negative test results from private laboratories. 

“We see this wax and wane. It’s not unusual for us to have times of, even just over a general weekend, where people don’t get tested or we don’t get reports in from different labs,” she said. “That’s why it’s so important that you look at percent positivity over a period of time, not just an individual day.”

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