That switch required state health officials to slightly increase the statistic known as the positivity rate, which Gov. Greg Abbott has repeatedly cited as a benchmark when deciding how fast to reopen the economy.
It also appears to have caught Abbott telling a big, fat whopper.
During a Monday press conference, a reporter asked the Republican governor whether the state was commingling antibody testing and live-virus testing numbers.
"The answer is 'no,'" he replied. "They are not commingling those numbers."
However, the Thursday change by the Texas Department of State Health Services means that the state had been doing precisely what Abbott denied.
TDSHS disclosed that, as of Wednesday, it had included 49,313 antibody tests in its tally of total tests, according to the Texas Tribune. Those antibody tests represent 6.4% of the 770,241 total tests reported up through that time.
Infectious disease experts caution against mixing together the two types of tests, saying it gives an inaccurate read on the data. Here's the fundamental difference between the two: antibody tests show whether someone was previously infected, while viral tests tell whether someone still has the virus.
Additionally, according to the COVID-19 Testing Project, some antibody tests have high rates of false positives.
"It is terrible. It messes up everything," Harvard University global health professor Ashish Jha told The Atlantic after Virginia officials were caught combining test results earlier in May.
The Texas Tribune did a deep dive on just how mixing the two tests skewed numbers in the Lone Star State. The short answer is that it led to a 0.41% increase in Tuesday's positivity rate.
Abbott's office was unavailable for comment Friday afternoon. However, during a TV interview the governor maintained that the commingling only happened for "about a 10-day period or so," the Tribune reports. Even with the revision, the positivity rate is still on a downward trend, he added by way of defense.
Despite that attempt to downplay, Abbott's political opponents pounced.
“More than 52,000 Texans have tested positive for this virus. Nearly 1,500 are dead. More than 2 million people have filed for unemployment in Texas," said Abhi Rahman, a spokesman for the Texas Democratic Party.
“Meanwhile, our governor continues to blatantly lie and manipulate data which puts our entire COVID-19 recovery in jeopardy. He has lied about the availability of testing and is now lying about the testing being done. This week has proven beyond a shadow of a doubt that Governor Abbott continues to mismanage the coronavirus crisis."
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