HealthcareIssuesStatewide NewsTexas Health Officials Separate Antibody and Viral Coronavirus Tests, Trends Change Little

Although the positive rate in cases was slightly inflated by the mixing of the two types of data, the general downward trend in rate was not affected.
May 22, 2020
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On Thursday, the Texas Department of State Health Services (DSHS) released new data that sorted out about 49,313 antibody tests that had previously been included in the total testing numbers along with the number of viral tests.

Antibody tests, also known as serological tests, are used to determine if an individual has begun producing antibodies in response to the novel coronavirus. The antibodies will typically only be discoverable late in the span of the infection or after a patient is fully recovered.

Viral tests are used to determine if an infection is currently active in an individual.

While combining the positive results of both types of tests is useful in showing how far the virus has spread throughout the state in total, the combination skews the trend lines used to deduce how fast the virus is currently spreading.

Despite Governor Greg Abbott’s statement at a press conference on Monday that DSHS was not “commingling” antibody and viral tests, the newly released DSHS data indicates that the data had indeed been mixed since May 13 — several days prior to the press conference.

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On May 13, DSHS reported the highest number of new tests to date: 49,259. With those test numbers came only 1,355 new cases, marking a low daily positive rate of 2.75 percent, well below the 7.5 percent average of the preceding week.

With the new data, it appears that the state added in about 30,700 antibody tests to the reported tests on that day. Excluding that number, the daily positive rate would be 7.29 percent — much more in line with the trend at the time.

However, that calculation is likely a little high, since there is no delineation between the positive viral tests and the positive antibody tests on that day.

Of the total 49,313 antibody tests, DSHS says that 2,114 are positive — a rate of 4.29 percent.

“The information that I have is for about a ten-day period or so, during which some antibody tests were coming in — it could have been a little bit longer than that — there was the inability for the counties to separate that out as it was received by the Department of State Health Services,” said Abbott in a Fox 7 interview when asked about the mixing of data.

Abbott went on to note that the addition of the antibody tests had a relatively small effect on the positive rate.

He used May 19 as an example, which saw the seven-day rolling average positive rate change from 4.29 percent to 4.70 percent with the removal of the antibody testing.

Abbott said that moving forward, DSHS would continue to report the antibody and viral test numbers separately.

The overall trends in the data, as Abbott also pointed out, have not significantly changed with the updated reporting.

However, some county officials have expressed concerns about a potential commingling of other numbers in the near future that could be even more misleading.

DSHS has recently updated their coronavirus case definition to include both laboratory-confirmed cases and “probable cases.”

Previously, only laboratory-confirmed cases were counted.

The new inclusion of probable cases leaves room for unconfirmed infections to be included in counts if a person meets certain criteria.

As Collin County Judge Chris Hill pointed out at a recent commissioners court meeting, failing to clearly delineate the two types of cases could cause an appearance in a drastic increase in the spread of the virus even if the true number of infections is declining.

A health official at the county meeting said that the cases would be distinguished, but it is unclear of when DSHS might make that data available.

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Daniel Friend

Daniel Friend

Daniel Friend is a reporter for The Texan. While recently finishing his degree in Political Science from Azusa Pacific University, he also interned in the U.S. Senate and co-authored a book on C. S. Lewis’s science fiction trilogy. In his spare time, he might be reading up on Dostoevsky or attempting to write a novel.