Texas is changing the way it publishes its accounting of coronavirus tests after the practice of conflating two types of tests was disclosed last week.
Until Thursday, the state was combining tests for antibodies and tests for active virus, which presented a skewed picture of Texas’ testing capacity and artificially deflated the rate of positive tests.
Active viral tests, or polymerase chain reaction (PCR) tests, are done using a sample of mucus from the respiratory system. Those tests are used to identify the presence of live virus. Antibody tests, meanwhile, are done using a blood sample. Those tests look for the presence of an immune response to the virus – an indication a person has had the virus at some point in the past. These tests have only recently become available, and there is evidence that they are unreliable.
KUT first reported that the state was mixing the testing numbers last Wednesday.
On Thursday, the Texas Department of State Health Services’ COVID-19 dashboard began including the number of antibody tests separately. The state reports 49,313 antibody tests going back to at least May 13. That represents about 6% of the total tests the state had reported previously.
Removing those tests from its calculation of the test-positivity rate pushed the state’s seven-day average up by about half a percentage point to 5.43%. That rate has been a crucial metric for determining how widespread the virus is and how well testing strategies are working. Gov. Greg Abbott is using the test-positivity rate as one of the major guidelines for his reopening decisions.
The state of Virginia was first revealed to be mixing its test numbers in an effort to inflate its testing numbers. Several other states, along with the Centers for Disease Control and Prevention, were also found to be doing this. Many states and the CDC have since stopped.
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