Around 43,000 people throughout England and Wales may have been inaccurately told that their polymerase chain reaction (PCR) Covid-19 test was negative due to errors at a private laboratory in Wolverhampton, England.
Testing at the lab has now been suspended after an NHS Test and Trace investigation.
The investigation took place following a number of reports of people testing positive for Covid-19 using lateral flow tests (LFTs) but negative after a follow-up PCR test. This caused confusion, as PCR tests are generally regarded as more precise than LFTs.
The UK Health Security Agency (UKHSA) has said that all negative results received from the lab, owned by Immensa Health Clinic, between 8 September and 12 October are being investigated.
Immensa was first established in May 2020 and has received a £120m government contract to provide testing services in the UK.
Affected test users are being contacted and asked to take another Covid-19 test. While the issue has mainly impacted people living in the South West of England, test sites throughout South East England and Wales that send their samples to the Wolverhampton lab for processing have also been impacted.
There were no technical issues with the test kits themselves, but with the processing being carried out at the lab.
UKHSA public health incident director Dr Will Welfare said: “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.”
Immensa said it is cooperating fully with the UKHSA investigation.