A new variant of Covid could be the cause of strange PCR and LFT results being reported by Brits across the country.
Dozens of people in the South West last week reported testing negative on their polymerase chain reaction tests (PCRs) after getting positive results for their lateral flow test (LFT).
The anecdotal reports have prompted public health officials to start a nationwide inquiry, the i reports.
The UK Health Security Agency (UKHSA) - responsible for public health - has refused to speculate whether a new variant could be the cause of the strange findings.
But they are working with two theories for what may have caused the false positives.
One theory is that a positive LFT followed by a negative PCR could mean the infected may have been exposed to a variant with a genetic mutation - known as the "S-gene dropout".
This means the spike protein - which the virus uses to attach itself to human cells - is missing.
Though the PCR test is the most accurate test available they can miss cases of the S-gene dropout.
The Alpha variant - which emerged in Kent in autumn last year - also had the S-gene dropout. It too indicated negative results in PCR tests for people with confirmed Covid infections.
The agency is also investigating if the LFTs are producing false negatives because subjects have been infected with a harmless form of the virus that has been known to circulate among humans for years.
While the UKHSA played down concerns of a new variant - due to the dominance of the Delta Strain - they are still investigating the possibility.
A Whitehall source who spoke to i refused to comment on what the cause could be.
Chief medical adviser at the UKHSA Susan Hopkins urged people who get the strange result to make sure to still take a PCR.
Dr Hopkins said: “We have been made aware of some areas reporting positive LFT test results with subsequent negative PCR tests and we are looking into the cause.
"If you get a positive LFT 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. With any test it is important to carefully read and follow the instructions for use on the test kit so as to avoid any incorrect readings.”
Dr Jenny Harries, the chief executive of the agency, said Delta has been dominating other variants across the world.
Dr Harries told Times Radio: “Where we’ve looked across the world even at variants which we have been concerned about and we are currently for example looking particularly at the Mu variant at the moment, where you see a surge in Delta it seems to be dominating other variants and a number of variants have now become extinct and have come off the worry list if you like.”
