Abbott can’t pick and choose his favorite COVID-19 data

Gov. Greg Abbott announced Monday that most Texas businesses, from bars to bowling alleys, will be allowed to reopen.

In a press conference updating Texans about the news, Abbott said he focused on two metrics to guide his decisionmaking: hospital capacity and the state’s infection rate.

Hospital capacity is ample, and the state’s infection rate — or the percentage of coronavirus tests that come back positive — has been declining.

In particular, the state’s infection rate has been showcased by Abbott in press conference after press conference as a sign that the state is beating the pandemic. But that metric has its limits, and it alone doesn’t tell the full story of Texas’ coronavirus curve. 

In an interview with the Signal, Texas A&M Pandemic and Biosecurity Policy Program Deputy Director Christine Crudo Blackburn said the state’s declining infection rate is a result of growing testing capacity.

That’s because testing at the start of the outbreak mostly focused on people who had obvious or severe symptoms, resulting in a particularly high infection rate.

“As testing expands, you would expect the number of positive cases to go down, especially as your testing expands broadly to the point where you can test mild cases or people who are asymptomatic,” Blackburn said.

In mid-April, the positive test rate in Texas peaked at almost 15 percent and then steadily declined to around 5 percent in recent weeks. Within that same timeframe, the average number of daily tests conducted in the state rose from under 10,000 to just shy of 30,000. 

“I don’t think it adds any value,” Blackburn said of relying on the state’s positive test rate alone to understand the pandemic, adding that it was better to focus on changes to trends in positive tests, hospital capacity and fatalities.

States considering reopenings have been offered two benchmarks to choose from by White House guidelines. One is a downward trajectory of documented cases within a 14-day period, which Texas is currently not meeting, and the other is a decline in the state’s infection rate within a 14-day period, which Texas is meeting. 

Republicans in the state have argued that the number of daily new cases, which have spiked in recent days, is not a sign that the state is prematurely opening but a result of an increase in testing. 

Of course, ramping up testing doesn’t just influence the number of confirmed cases, it also affects the state’s infection rate, the metric Abbott prefers to tout. As Blackburn and health officials have noted, more widespread testing means a fewer share of tests coming back positive.

“If you want to interpret [the positivity rate] as a hint to prevalence in a particular location, you have to assume lots of other things stay constant,” Daniel Westreich, an epidemiology professor at the University of North Carolina told The Atlantic recently.

“We just haven’t tested enough people yet,” he said. “If you were doing random screening of the whole population, we just don’t know what you’d see. We don’t know how many asymptomatic viral shedders are out there.”

This is an acute problem in Texas where testing still lags far behind other states. Worse, the testing numbers and the metrics derived from then may also be muddied by the possibility that Texas is reportedly inflating its testing numbers by including antibody tests.

Abbott and other Texas Republicans will need to be more upfront about the data they’re picking to reassure Texans. A declining positive test rate is not an infallible figure, and the number of rising daily new cases and deaths, as well as the undented number of Texans being hospitalized, can’t be ignored.

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