More than 110 "major incidents" have hit hospitals across England in the past four months, after parts of the health service went live with systems supplied under the £12.4bn National Programme for IT (NPfIT) in the NHS.
Many of the incidents, which have been reported by Connecting for Health, the body that oversees the NPfIT, involve the failure of x-ray retrieval hardware and software, known as Pacs (picture archiving and communications systems) which allow clinicians to view digitised x-rays on screen.
When these systems fail, it can stop doctors viewing x-rays on screens in wards and operating theatres.
The major incidents also involve hospital patient administration systems, which hold patient details such as appointments and planned treatments.
The specifications for services to be supplied under the NPfIT built up an expectation among NHS staff and clinicians that they would receive sub-second response times, and that equipment would be available to them 99.99% of the time.
But the list of major incidents seen by Computer Weekly shows that in some cases NHS staff and clinicians have lost access to their main hospital systems. More than 20 major incidents have affected multiple NHS sites.
This raises questions about whether the risks of failure after go-live have been adequately assessed, and whether any independent regulator has an overview of the riskiest implementations across England.
An IT director who declined to be named for fear of repercussions wrote to Computer Weekly about the problems. He said, "Some NHS trusts that have implemented Connecting for Health [centrally-bought] solutions are struggling to cope with poor system performance and service availability issues.
"The local service provider is working flat out to resolve the issues. However, a great deal of damage has been done in terms of deteriorating end-user confidence and satisfaction with respect to the systems."
The high number of incidents could be because the programme is in its early stages and systems are bedding down - the 10-year supplier contracts have run for less than three years.
However, the systems installed so far are basic early releases which have only a small number of the planned features. Most safety-related clinical systems, such as the e-ordering of test results and the prescribing of drugs, which will generate the bulk of transactions, have yet to be implemented.
Once they are, "major incidents" could potentially affect many more patients than those that have hit the NHS this summer.
Some of the listed incidents were fixed quickly, though others lasted much longer. The crash of a datacentre in Maidstone in July which caused the loss of central services and systems to 80 trusts in England for up to four days, is among those listed.
The Maidstone crash is described in the list of major incidents simply as "North West and West Midlands Lorenzo users connecting via Maidstone unable to access system due to datacentre power failure". Lorenzo is a system supplied by CSC and its software contractor iSoft.
Fujitsu, CSC and BT are shown as having been the main supplier in most of the major incidents.
A spokesman for Connecting for Health, said, "The expression 'major incident' can be misinterpreted. For example, this could be when a patient administration system is running slow, or there may be problems with the local network."
The spokesman added, "We are open and transparent about service availability. We believe we are unique among comparable organisations in that we publish service availability updates on our website showing the service levels achieved by suppliers.
Any interruption to service is unfortunate but trusts have tried and trusted manual systems to provide continuity of care.
"Service availability is typically much higher than for systems procured before the NPfIT."
However, information on major incidents is not readily available on the Connecting for Health website.
Read article: Was Audit Office report on NHS IT truly independent?
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