A Covid-19 test that gives results in just 20 minutes has been confirmed as having high sensitivity to the virus - despite reports on the contrary.
Amid scepticism about the accuracy of the rapid turnaround results, the government has defended the tests - set to be rolled out to university students heading home for Christmas later this month.
An evaluation carried out by NHS trusts and universities found the OptiGene RT-Lamp test to be effective in identifying infectious cases - including for people not displaying symptoms.
The findings follow a report by the Guardian that the test identified only 46.7% of infections during a trial in Manchester and Salford.
In a letter seen by the newspaper, scientists from Greater Manchester’s mass testing group (MTEG) said they had “significant concerns” and felt the data did not support a large-scale rollout of the tests to staff in clinical settings.
The Department of Health and Social Care (DHSC) said that as part of a strategy to deliver asymptomatic testing, the test was used for NHS staff and in pilots in Southampton, including at the University of Southampton.
Initial results from the pilots showed the test as effective in identifying positive cases and breaking chains of transmission, according to the department.
The test was found to have a sensitivity of 79% and specificity of 100%.
This means it is effective in identifying cases who are infectious and are most likely to transmit the disease, the DHSC said.
In samples with a higher viral load, the sensitivity of the test increased to 94% for saliva and 100% for swabs.
Pregnancy-style lateral flow tests - that give results in minutes and can be carried out without supervision - are part of a pilot mass testing scheme in Liverpool.
But some experts have urged caution, saying rapid tests are not as accurate as standard PCR swab tests processed in a lab.
It is feared the quick turnaround tests could result in people who are infectious being told they are not.
The government defended the tests - saying that unlike PCR tests, OptiGene RT-Lamp tests do not require sequential changes of temperature and so can produce results more rapidly.
Health minister Lord Bethell said: "With up to a third of individuals with Covid-19 not displaying symptoms, we are rolling out asymptomatic testing to protect those at highest risk."
He continued: "By broadening testing to identify those showing no symptoms and who can infect people unknowingly, we can find positive cases more quickly and break chains of transmission.
"We are using the latest technology to do this, and the country’s leading scientists have rigorously evaluated the Optigene Lamp test in the lab and in the field and confirmed its sensitivity for asymptomatic testing."
Professor Dame Sue Hill, chief scientific officer for England in NHS Test and Trace, said: "It has been effective in the pilot study sites and can make a valuable contribution to our overall Covid-19 testing capability."
Professor Keith Godfrey, of the University of Southampton MRC Lifecourse Epidemiology Unit, who led the first phase of the Southampton saliva testing pilot, said the test was "very easy for students to use".
"During the pilot, with regular testing and participation rates exceeding 80% among the school staff and students, there has been no evidence of any transmission of infection within the schools involved," he said.
Prof Godfrey said "feedback" from those taking the test had been "amazingly positive."