250,000 smear tests were sent to unapproved labs
Dr Gabriel Scally found 91,000 tests were read in a Manchester lab which was not accredited
As many as 250,000 smear tests from women in Ireland were read in labs in the US and the UK which were unapproved and not inspected by CervicalCheck.
The shocking extent of the transfer of slides to locations such as Grand Rapids, Michigan; Lansing, Illinois; Hawaii; and Manchester, England, was revealed in the second investigative report of Dr Gabriel Scally.
Until last year CervicalCheck was only aware of six labs which were officially being used to carry out its cervical screening, but Dr Scally found the real number was 16 with 10 unapproved centres used. All but one was accredited.
Major concern emerged about the lab based in Salford, Manchester, where 91,000 tests were examined.
Dr Scally found it started taking tests from CervicalCheck in 2016 but was not independently accredited - to ensure it met standards - until two months ago, on his request. The UK facility, operated by Medlab in Dublin, started with just one laboratory scientist and now has only four staff.
Dr Scally said: "I find the circumstances surrounding the screening of Irish women's slides in Salford particularly surprising, and disturbing, in terms of the level of governance expected in a public health programme."
Although all four staff have their outcomes recorded by Medlab in Dublin, he said he was of the view that remote working by a very small number of staff should be avoided.
Dr Scally said that he could not find any evidence of quality deficiencies in any of the unapproved labs but he also said there were gaps in some of the data he had access to.
"We have not identified any evidence that the lab services used in the past or those currently used by CervicalCheck have provided, or are providing a service which does not meet acceptable standards in their country," he said.
Some of the labs have now closed.
The largest outsourcing was carried out by CPL, based in Austin, Texas, which worked for CervicalCheck from 2010 to 2013. It sent tests to San Antonio, Las Vegas, Victoria, Hawaii and Florida. Dr Scally remarked the distance between these labs was often considerable - Honolulu is 6,000km from Austin.
The name of the US lab was included in a letter to a woman's GP but not to CervicalCheck.
CPL defended the move on the grounds it had a spike in tests and wanted to maintain turnaround times.
Dr Scally said there was no written evidence of CervicalCheck being notified of the outsourcing, although Medlab said the UK lab was mentioned at a meetings.
He criticised the failures in CervicalCheck's quality assurance which failed to pick up on the additional labs.
He had previously described its surveillance as virtually non-existent.
The early rounds of visits to the main labs by CervicalCheck inspectors were limited and "opportunities were missed" to develop a quality assurance process, he added.
Medlab also failed to tell the Irish watchdog responsible for inspecting labs, the Irish National Accreditation Board, the UK facility was operational in 2016, 2017 and 2018.
Health Minister Simon Harris said he "hoped Dr Scally's comments will reassure Irish women that they can trust the results they receive from the CervicalCheck programme and that they should continue to attend for their scheduled screenings".
Commenting on the findings, CervicalCheck campaigners Lorraine Walsh and Stephen Teap said the report was "disturbing".
Mr Teap said he had his late wife Irene's test result at home.
It says Austin, Texas, on it, as does the result of every other woman who got their slides done through CPL. "But the problem is, we don't know where they were read," he said.
Vicky Phelan, who settled her case against CPL, hoped the review of over 1,000 slides by the Royal College of Obstetricians and Gynaecologists would provide more answers.