An estimated 43,000 people may have been given wrong negative PCR Covid test results, the UK Health Security Agency has said.
NHS Test and Trace has suspended testing operations provided by Immensa Health Clinic Ltd at its laboratory in Wolverhampton, following an investigation into reports of people receiving negative PCR test results after they have previously tested positive on a lateral flow.
The errors relate to test results given to people between September 8 and October 12, mainly in the South West of England.
There are no technical issues with test kits themselves and people should continue to test as normal, UKHSA said.
It said a full investigation is being carried out into why and how incorrect results were given.
NHS Test and Trace estimates that around 400,000 samples have been processed through the lab, but new samples are now being redirected to other labs.
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.
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.”
It comes after members of the public were urged to book for further testing after some PCR tests at a testing site in Newbury after they received false negatives.
West Berkshire Council said in a statement some of the tests at the Newbury Showground testing site, operated by the Department for Health and Social Care (DHSC), “have had results sent out that may have incorrectly shown as negative for Covid-19”.
“After receiving reports from local residents in recent weeks that there were concerns about the accuracy of test results from the site, we passed these concerns onto the DHSC for further investigation,” the statement added.
Testing continues to remain important as we learn to live with Covid
“The DHSC has now confirmed that a number of sites nationally may have been affected by this issue, including the one at Newbury Showground.”
Those who received a negative result for a PCR test between October 3 and 12, as well as their close contacts, were “strongly” encouraged by the local authority to take another test.
Councillor Graham Bridgman said: “Testing continues to remain important as we learn to live with Covid and anyone who has symptoms, or who has been in contact with someone who tests positive, should book a PCR test straightaway. We also strongly encourage the public to do twice weekly lateral flow testing.
It comes as fully vaccinated people arriving in England from countries not on the red list have been told they can take a cheaper and quicker lateral flow test rather than the PCR version from October 24.
The DHSC has been contacted for comment.