Orange County mistakenly included serology tests in its cumulative count of coronavirus tests administered for five weeks beginning in late April, then failed to correct the figure for another three weeks after the error was discovered, health officials said Thursday.
The oversight resulted in 30,000 serology tests being added to the “cumulative tests to date” figure reported on the O.C. Health Care Agency website between April 28 and June 3, said Dr. Clayton Chau, the agency’s director.
But the mistake did not result in an erroneous increase in the number of positive COVID-19 cases reported, officials said.
Serology tests, also known as antibody tests, are meant to identify if someone has had a previous immune response to the virus, not if they’re currently sick. Active infections are diagnosed using polymerase chain reaction, or PCR, tests.
“I would like to sincerely apologize for any confusion on this matter that has caused for the community,” Chau said during a briefing Thursday. “In the future, I and my team would ensure that we will continue to do a better job to be more transparent with respect to the data that informs policy and personal health decision on our residents.”
Chau said his team failed to sort out the serology tests when the state reporting system — the California Reportable Disease Information Exchange (CalREDIE) — added serology tests as auto-processed tests on April 28. O.C. health officials rely on the state portal to download local data.
“My team capture this test results as part of their all COVID tests report, an error that leadership became aware of around June 3,” Chau said.
Officials did not explain how the issue came to their attention. They also have not provided a breakdown on the number of serology tests mistakenly added per day.
Officials say the 30,000 tests added to the total by that point did not affect the county’s positivity rate, which was correctly pulled from state data. It also didn’t have any impact on the county’s attestation to the state on its readiness for reopening businesses, Chau said.
O.C. reports the total number of tests administered, rather than how many individuals have been tested. That practice has also met criticism from experts who say it can make testing appear more robust than it actually is; people at higher risk, such as nurses, may get tested multiple times a week.
After the county realized the data mistake June 3, it stopped adding serology tests to its cumulative total tests figure. But the 30,000 already added weren’t dropped from the number until June 26, when the O.C. Health Care Agency launched a new COVID-19 data dashboard.
Chau said the lag was because “several changes to data reporting were in process, including changes to reporting of test numbers.”
The county Board of Supervisors didn’t become aware of the error until it was reported in the O.C. Register Thursday morning, according to Chair Michelle Steel.
Steel said she’s asked Chau to begin reporting antibody tests on its dashboard “so that all the data will be clear and trackable to us and to public.”
The public health director took the blame for not informing the board.
“Because it was not calculated into our number, I didn’t think that it would be that significant,” Chau said. “But I learned, right?”
Frank Kim, the county’s executive officer, said he was also aware of the problem and called it a “mistake” that he did not advise the board. But he said he didn’t think it should impact the public’s trust in health officials.
“I think the county has always been very transparent,” he said. “And when there are mistakes made or reporting inaccuracies, we’ve always come out forward and we’ve shared them with you.”