The blunder in computing that meant that thousands of women did not undergo bad cancer screening could take place in 2005, one expert warned.
The crude warning could worsen the scandal that caused 450,000 women not to receive an invitation for their last routine evaluation. delivering up to 270 an early death.
When the flaw came up this month, Health Secretary Jeremy Hunt said the computer error dated back to 2009.
But Professor Peter Sasieni, a cancer screening and prevention researcher for the King & # 39; s College of London, believes that the problems could have started as early as 2005.
Professor Sasieni studied the data of the bad cancer screening program between 2004 and 2017.
He observed the number of women eligible for bad cancer. that invitations were sent every year from 45 to 70.
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In a letter published in the medical journal The Lancet, Professor Sasieni said that between 2004 and 2005, the number of invitations sent to women aged 65 to 70 was "very low".
This coincided with the time when the program was extended to the age of 70 years.
One third of eligible women should have been invited each year.
But Professor Sasieni said that the figures showed that it was 31% in 2005-06, reaching almost 35% in 2016 -17.
In comparison, between 34% and 38% of people aged 50 to 64 years were invited each year.
The difference meant that more than 500,000 may have lost invitations since 2005, he concluded.
The letter says: "Data that could alert people to the number of invitations that were sent to women in their 70s, less than expected." Cly available, but no one watched them carefully.
"Part of the fault it lies in the way the data was presented.
"But it is also not clear who is responsible for controlling such results".  Public Health England dismissed the "defective" findings.
Professor John Newton, director of health improvement at PHE, told the BBC: "This is a flawed badysis that does not take into account some important facts, such as when the bad screening program was launched all those in their 70s in England or when a clinical trial called Age X was started. "
He said that PHE focused on supporting those who were not invited to their final evaluation.
An independent has launched a review of the computer error, which according to Hunt, was discovered in January.
The Mirror revealed this month that the error was marked by NHS funds last year.