WASHINGTON — After a faulty formula led to unreliable Zika test results at a D.C. lab last year, the retesting of all affected samples has concluded.
The D.C. Department of Forensic Sciences said that two women and a man, who had tested negative, have been told that they in fact tested positive for the Zika virus. Among the three testing positive for the virus, which is linked to birth defects, was a pregnant woman, the department confirmed.
A total of 423 samples were retested at three other public health labs. The Centers for Disease Control and Prevention said that 394 maintained negative test results and that 26 samples were inconclusive.
All the people who tested positive for Zika — and those with inconclusive results — have been notified, the department said.
Last year, the D.C. public health lab said it discovered that a lead scientist made an error when entering a testing formula into a spreadsheet. When that was discovered, the department made the choice to turn all Zika testing over to the CDC.
“We have retooled the test and are ready to re-implement testing following review from our Science Advisory Board,” Dr. Jennifer Smith, director of the Department of Forensic Sciences, said in a statement.
A federal audit found that the CDC sent out instructions that didn’t meet federal regulatory standards.
According to testing requirements from the Clinical Laboratory Improvement Amendments, an additional negative control should have been used during testing, and DFS said that was not mentioned in the guidance. The CDC has since revised its instructions, the department said.
Throughout the audit and inspections, DFS said, the lab has held onto its certification, because all corrective actions have been taken.
Right now, the CDC continues to conduct the District’s Zika testing, but the District has been given the green light to resume testing for the virus in-house. It’s not clear when DFS plans to resume testing of Zika samples.