Scores of operations were cancelled at hospitals in Leeds and Bradford and routine testing by local GPs was suspended.
Lessons from the incident at one of the busiest NHS laboratories in the UK are being shared across the country amid growing concerns over a backlog to replace outdated NHS IT systems as budgets for capital investment face real-term cuts.
An independent report into the crisis points to a mix of technical problems and human error using the Telepath system which has been in place at Leeds General Infirmary since the early 1980s and is used across the health service.
Test results could not be reported electronically and staff were forced to record them on paper for delivery by hand to clinicians.
A backlog of 10,000 tests developed at one stage in the pathology laboratories before other hospitals stepped in to deal with samples during the outage in September.
Cancer patients were among those hit as more than 150 operations and 170 outpatient appointments were postponed. GP patients faced delays in results or were even required to repeat blood tests.
The system was not fully restored for more than two months after it was discovered data had not been backed up in some cases since 2010 as the ageing technology struggled to deal with increasing volumes of information.
The report says “like many acute hospitals in the English NHS”, there are systems in Leeds reaching “‘end of life’ or where significant investment is needed to bring them up to modern day standards”.
It adds: “Whilst the Telepath system still provides a valuable service, continues to have a reasonably large UK user base and is well known to pathology IT professionals, it is old, difficult to maintain and is probably in need of replacement.”
The report found a series of malfunctions over a short period caused the system to fail but warning light signals went unnoticed by staff.
The report makes 10 recommendations including better checks of all critical systems in hospitals in Leeds.
It said the system was supported in Leeds by a “diminishing number of dedicated personnel” but over the years key posts had been lost “along with associated corporate memory” of a system dating back three decades.
It found the IT team at the hospital did not know the time taken to back up data had doubled to more than six hours. A second back-up of information started and finished before the first had been completed which meant data was missing.
Officials at Leeds Teaching Hospitals NHS Trust are drawing up a case for major IT investment amid one estimate last year that work worth £40 million is required.
Its chief medical officer Yvette Oade said: “It is extremely regrettable that these errors occurred as this incident created a great deal of inconvenience and concern for our patients and our partners.
“Already we have put in place a robust monitoring system to ensure that all system warning indicators across the trust are identified and acted upon immediately and we have improved the back-up processes within the Telepath IT system.
“The system is now fully restored and working well and immediate actions have been taken to address the causes of the failure.
“There are no immediate plans to replace the system but we are already in the process of a full review of our IT requirements across the trust.
“Securing additional funding to invest in our IT infrastructure continues to be one of our main priorities.”
Hospital chiefs in Bradford had already planned before the crisis to end its pathology partnership with Leeds. A new collaboration with Airedale NHS trust went live two weeks ago.