Abbott’s key metric in virus fight unreliable
True positivity rate is thrown off by backlog of tests due to coding errors by private firms
AUSTIN — As schools begin to reopen and Gov. Greg Abbott faces pressure to relax shutdown measures, it is impossible to determine where Texas stands on a COVID-19 metric that has guided the governor’s decisions on when to tighten or loosen restrictions on businesses and public activity.
Over the last week and a half, the state began reporting coronavirus data from a backlog of 500,000 viral tests that officials say accumulated because of coding errors by Quest Diagnostics, Walgreens and CHRISTUS Health — all private entities that process the tests.
The result has been an ongoing miscalculation of the positivity rate, the rate at which people test positive for the virus.
Last week, it reached as high as 24.5 percent and suddenly dipped back down again to about 11 percent this week as more backlogged tests were included in the data. Abbott has said a sustained positivity rate below 10 percent would allow for further reopenings in the state.
The influx of backlogged tests, dating as far back as March, has also exposed a convoluted reporting system that requires state officials to receive lab results, send them back to counties and wait for them to return to the Texas Department of State Health Services before counting them.
The result is a mess of information reported recently to the public in “data dumps” that include test results from months earlier, skewing statewide coronavirus statistics and positivity rates.
“The timing of it is horrible because it’s right at the beginning of opening the schools, when you want your data to be as accurate as possible, and it’s not,” said Darrell Hale, a Republican commissioner in Collin County.
The county on Wednesday pasted a disclaimer to its COVID-19 reporting site declaring “no confidence” in the state’s numbers, which Hale said have ballooned in recent days even as lab-confirmed COVID-19 hospitalizations have declined.
Denton County on Wednesday said it would also no longer report
a daily positivity rate, as its health department recently received more than 800 previously unreported positive tests from the health services department that are more than a week old.
The effect of the backlog is different in each of Texas’ 254 counties, which rely on the state’s numbers in different capacities. Some larger counties directly receive test results from outside labs and manage their own positive cases, allowing them to calculate a countywide positivity rate.
Statewide, the number of people hospitalized with COVID-19 has been falling slowly since midJuly, an encouraging, albeit delayed, sign of the current status of the pandemic. The positivity rate in large counties including Harris has remained above 10 percent, according to their local dashboards.
Last week, the governor said health officials were “investigating” the statistics as the number of positive cases climbed but the number of people tested fell. It’s unclear whether the investigation has been completed, but Abbott said Wednesday that the issue had mostly been resolved, and he is “more confident than I was before about the numbers.”
Abbott faulted private labs for the glitches, as well as technological issues in the state’s own reporting system, which did not have the capacity to process more than 48,000 tests per day until Aug. 1. The state did not disclose the issue as it built up throughout July, when as many as 67,000 tests were conducted each day.
“There may be, still, another day or two while that info is leveled out, but by the time this week ends, we should have pretty accurate data,” Abbott said during an interview with Dallas’ KXAS.
As of Wednesday, the sevenday coronavirus positivity rate stood at 10.8 percent — a slight dip from the day before, according to the most recent data from the state.
An Abbott spokesman did not respond to a request for comment on whether the governor trusts the current positivity rate and whether he still plans to use the metric as a threshold for reopening bars.
One backlog after another
DSHS spokeswoman Lara Anton said the state has been working on the backlogs for the entire month of August. The first backlog, caused by the state’s inability to process more than 48,000 tests daily, was cleared in the days after a system upgrade on Aug. 1. The state had 346,000 tests in that backlog.
Then came the backlog attributed to coding errors as tests were reported from private labs. Anton said the issues were identified over the past several weeks — 354,000 backlogged tests from Quest Diagnostics, 95,000 from CHRISTUS Health and 59,000 from Walgreens.
Once the state was able to begin processing the 500,000 backlogged tests from private firms, it filtered the results down to the counties to check for duplicate cases, address mistakes and other errors, Anton said. But each local health department reports the results to the state and to the public
“You don’t know what this kind of backlog means for the positivity rate. To call it a positivity rate is really a bit of a push.”
Diana Cervantes, epidemiologist
differently — some separating old and new cases, some grouping them together, she said.
That discrepancy could cause the state’s most recent testing numbers to include infections from weeks or months ago, painting an inaccurate portrait of the current state of the pandemic.
Anton said there is no way to know the true positivity rate or how much of the backlog has been cleared, since the counties also do not report back how many old tests they have worked through. The state has since hired outside consultants from Deloitte and Persivia to help parse through the data and decide whether to overhaul the current numbers reported by the state, she said.
“We’ve got a team of data consultants helping us right now,” Anton said. “They’re helping us figure out how we can streamline it, identify errors that could cause a backlog sooner.”
The majority of the backlogged cases, she said, including all of those from Quest, were from June and July — likely indicating that the state’s resurgence of coronavirus cases earlier this summer was worse than previously indicated.
But even those numbers are a point of contention. Quest Diagnostics said in a statement that it identified and resolved the coding issue by mid-May and did not respond to a request for clarification when asked why the state reported that most of their backlogged tests came from June and July.
Walgreens said it was notified of the coding error on Monday — two days after Anton said the state began processing the tests — and “immediately assessed” the problem, which has now been fixed. CHRISTUS said DSHS “recently asked us to resubmit records in an amended format.”
Anton and the commercial labs stressed that the reporting errors did not impact patients, who were notified directly of their testing results.
The state’s outdated and decentralized reporting structure has impacted the positivity rate since day one, said Diana Cervantes, the director of the epidemiology program at the University of North Texas Health Science Center in Fort Worth and former epidemiologist for DSHS and Tarrant County. The number of new COVID-19 infections comes from local health departments, while the number of tests conducted comes from the state and can be from a different time period, so “the numerator and the denominator are not from the same place, which has always been an issue,” she said.
Pivotal time
The backlogs only further agitate an already troubled system.
“You don’t know what this kind of backlog means for the positivity rate,” Cervantes said. “To call it a positivity rate is really a bit of a push.”
But parents depend on those metrics to send their kids back to school, and business owners use them as a marker to reopen their doors. Anton said that because Texas is so large, the statewide positivity rate might not be relevant in local reopening decisions.
“They would need to work with their local officials and talk about what’s happening in their communities,” she said.
In smaller counties, which rely on the state to oversee case management, the backlog could mean that contact tracing wasn’t performed when positive tests were identified.
During a daily briefing in San Antonio on Wednesday, Dr. Golareh Agha, the chief of informatics in the city’s health department, said the backlog is a “challenge” but wouldn’t say whether she had lost confidence in the state’s data.
“We process our own numbers after verifying what the state gives to our jurisdiction,” Agha said. “We trust our numbers.”