An estimated 43,000 people may have been given wrong negative PCR Covid test results, the UK Health Security Agency (UKHSA) has said.
The issues was identified at the Immensa Health Clinic Ltd’s laboratory in Wolverhampton, where testing operations have been suspended by NHS Test and Trace.
UKHSA says those affected were given results between 8 September and 12 October.
At the Newbury Showground testing site, the council says the issues affects people who took a PCR test between 3 October and 12 October.
The findings come after an investigation was launched into reports of people receiving negative PCR test results after they have previously tested positive on a lateral flow.
Test and Trace is contacting people who could still be infectious to advise them to take another test, while close contacts who are symptomatic will also be advised to take a test, as is already recommended.
There are no technical issues with test kits themselves and people should continue to test as normal, UKHSA said. They added that a full investigation is being carried out into why and how incorrect results were given.
Dr Will Welfare, public health incident director at UKHSA, said: “We have recently seen a rising number of positive LFD (lateral flow) results subsequently testing negative on PCR.
“As a result of our investigation, we are working with NHS Test and Trace and the company to determine the laboratory technical issues which have led to inaccurate PCR results being issued to people.
“We have immediately suspended testing at this laboratory while we continue the investigation.
“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.
“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.”
Andrea Riposati, chief executive of Immensa Health Clinic Ltd, said: “We are fully collaborating with UKHSA on this matter.
“Quality is paramount for us. We have proudly analysed more than 2.5 million samples for NHS Test and Trace, working closely with the great teams at the Department for Health and UKHSA.
“We do not wish this matter or anything else to tarnish the amazing work done by the UK in this pandemic.”