The UK Health Security Agency announced on Friday the suspension of operations at a private coronavirus-testing lab in Wolverhampton, central England, after at least 43,000 people were potentially given false negatives.
The Immensa Health Clinic had its operations suspended by NHS Test and Trace after an investigation into reports that people received negative PCR test results despite previously testing positive on lateral flow devices (LFDs).
Around 400,000 samples were processed by the laboratory, NHS Test and Trace said, though an estimated 43,000 could have been given false negative PCR test results between Sept. 8 and Oct. 12. Most of these incorrect results would have been from southwest England.
NHS Test and Trace is contacting those who could still be infectious and advising them to take another test.
The UK Health Security Agency (UKHSA) said the event was "an isolated incident attributed to one laboratory but all samples are now being redirected to other laboratories." It added that other labs were "working normally."
Samples that would have otherwise gone to the lab are now being redirected to other facilities.
Dr. Will Welfare, public health incident director at UKHSA, said: "We have recently seen a rising number of positive LFD results subsequently testing negative on PCR."
"There is no evidence of any faults with LFD or PCR test kits themselves and the public should remain confident in using them and in other laboratory services currently provided," he added.
"If you get a positive LFD test, it's important to make sure that you then get a follow-up PCR test to confirm you have COVID-19. If you have symptoms of COVID-19, self-isolate and take a PCR test," he said.
Shadow Health Secretary Jonathan Ashworth said: "Serious questions have to be asked about how this private firm -- which did not exist before May 2020 -- was awarded a lucrative £120 million ($165 million) contract to run this lab. From duff PPE to failing test kits, ministers have sprayed around tax money like confetti and utterly failed to deliver the service people deserve."
Immensa Health Clinic chief executive Andrea Riposati said: "We are fully collaborating with UKHSA on this matter. Quality is paramount for us. We have proudly analysed more than 2.5m samples for NHS test and trace, working closely with the great teams at DHSC (Department of Health and Social Care) and UKHSA. We do not wish this matter or anything else to tarnish the amazing work done by the UK in this pandemic."
Welsh Health Minister Eluned Morgan also said that 4,000 Welsh residents may have been affected too, most of whom are from south Wales.
Meanwhile, British government data published on Friday showed there were a further 44,932 positive cases, bringing the total since the start of the pandemic to over 8.3 million. There were also a further 145 deaths, bringing the total to 138,379.
Up to and including Oct. 14, over 49.3 million British people aged over 12 -- 85.8% -- have received their first dose of vaccine, and over 45.2 million, or 78.8%, their second dose.