EXPLAINED: What caused the huge swing in Texas’ coronavirus positivity rate this month?

(AP Photo/Matthias Schrader file) (Matthias Schrader, Copyright 2020 The Associated Press. All rights reserved.)

HOUSTON – After days of hitting record-high positivity rates in Texas last week, the numbers fell dramatically. State health officials said that fluctuation was caused by problems in data being reported by some labs.

On Aug. 7, the seven-day positivity rate hit a record of 19.41%. That number continued to climb until it hit an all-time high of 24.5% on Aug. 11. The next day, the rate plummeted seven points and fell to 11.25% on Aug. 15.

Lara Anton, of the Texas Department of State Health Services, said that rollercoaster rate was caused by coding errors on data that was being entered by three labs in Texas — Walgreens, Christus Meditech and Quest Diagnostic. The error prevented 500,000 test results from being properly uploaded to the state’s database, Anton said.

Anton said there is not a standardized way that labs report testing data, so the state uses software to format the reports so they can be input into the state’s database. She said that if the software cannot properly format the data, the result is an error code.

Anton said the errors have since been resolved are results are now being properly entered into the system, but the positive tests that were part of the backlog have to be checked by local health departments to make sure the tests are not counted twice.

Officials are now working on a system that can identify these types of errors sooner and prevent another backlog, Anton said.

Anton said most of the results in these half-million tests were negative, and the errors did not prevent anyone from receiving their results.

What the labs are saying

Explanations from the labs named by Anton varied widely.


Erin Loverher, of Walgreens, said there was a discrepancy in the coding requirements of the data being reported by the company and that the issue has since been resolved.

“This issue in no way affected the accuracy of the test results or the timely reporting of test results to patients,” Loverher said in a written statement.

Quest Diagnostic

A spokeswoman for Quest blamed the issue on a server being switched by the state without informing the company of the change.

“We were first alerted on May 7 there was an issue,” the spokeswoman for Quest said in a written statement. “We immediately worked with Texas DOH to trouble shoot the issue that day. The data feed issue has since been resolved.”

Christus Meditech

Christus Health officials said they had not been told by the state that there was a problem with the data.

“As part of our normal data integrity efforts, we constantly review our data submitted to all third party entities to ensure we have accurate public reporting,” Christus Health officials said in a written statement.


This story has been corrected to reflect that only the positive tests that were part of the backlog must be verified by local health departments.

About the Authors:

Award winning investigative journalist who joined KPRC 2 in July 2000. Husband and father of the Master of Disaster and Chaos Gremlin. “I don’t drink coffee to wake up, I wake up to drink coffee.”