IT problems at one of UK's most respected hospital trusts has led to a backlog of at least 14,000 London patients on a waiting list for treatment.
The backlog affects patients at St Bartholomew's (Barts) Hospital and The London NHS Trust, which serves two million people in east London, the City, and Canary Wharf.
Barts, which describes itself as world renowned, has 22,000 electronic patient records on its waiting list of people who should be treated within the national target of 18 weeks. Many are duplicates, but at least 14,000 are considered by trust staff to be the records of individual patients.
The trust says dealing with the backlog may mean some patients end up waiting more than 26 weeks for an operation, in breach of government targets.
Doctors say there are inaccuracies in data, the system can be slow and staff do not always understand the work-arounds, and the way the system works in combination with the trust's practices.
They add that, unless they fully understand the system's characteristics, they may find the data hasn't gone to the right place for the patient to be treated.
Barts and The London NHS Trust told Computer Weekly: "It has been a frustration for everyone at Barts and The London NHS Trust that our desire to meet the 18-week national target has been compromised by previous weaknesses in our information management and administration systems. The Trust has no evidence, however, that any patient has come to clinical harm because of the backlog."
Since installing the Cerner Millennium Care Records Service in 2008, as part of the NHS's National Programme for IT (NPfIT), staff and doctors at Barts and The London NHS Trust have lost track of thousands of patients on its waiting lists.
Some in the NHS are surprised the IT problems at Barts have continued for nearly 18 months. In June 2008, Barts said: "the outstanding issues resulting from the implementation of Care Records Service are in the process of being resolved".
Barts' 18-week waiting list backlog reached 26,640 in August. This had been cut to 22,000 patient cases by the end of last week. From these 22,000 staff and doctors are unable yet to tell which patients have had treatment within the government's 18-week standard.
The main health authority in the capital, NHS London, said in a statement to Computer Weekly: "Barts and the London are working to address a potential backlog of around 23,000 patient records to determine those who have been treated within 18 weeks and those who have breached this standard."
The strategic health authority is meeting monthly with the Trust and its commissioning PCT to ensure that this backlog is addressed."
Computer Weekly has also learned that Mike O'Brien, the health minister responsible for the NPfIT and the 18-week standard, is receiving fortnightly reports on the efforts at Barts and The London to reduce the backlog.
The problems at Barts - and at other London hospitals which run the Cerner Millennium Care Records Service - could undermine a decision to resume a roll-out of the NPfIT system after a halt last October. The next hospital in line for the system is Kingston Hospital NHS Trust.
The Department of Health's website says nobody should wait more than 18 weeks for the start of their treatment, from the time they are referred by a GP, unless they choose to wait longer or it is clinically appropriate to wait longer.