Hundreds of Londoners have waited longer than they should have for their first hospital appointment, as staff at Barts and The London NHS trust struggle to keep track of patients on their IT systems.
The waiting list delays during March at Barts and The London were the worst in the country.
The Government has set a target that all patients should see a consultant or doctor within 13 weeks of a referral by a GP.
Most trusts in England reported to the Department of Health "zero" patients in March who had waited longer than 13 weeks for their first outpatient appointment.
But the latest papers presented to the Board of Barts and The London said that it had 834 patients who were still waiting in March - and 675 of these had been waiting more than 17 weeks.
The number of patients waiting was higher than all the trusts in England put together.
Computer Weekly understands that some of the patients have shown up incorrectly on the waiting list - they had duplicate e-records and were actually seen but not recorded as being seen on their duplicate file. Other patients gave up waiting and were referred by their GP to another trust.
Still, hundreds of Barts' patients were still waiting for their first appointment after a GP referral, for weeks and sometimes months beyond the Government's 13-time limit.
Staff at Barts and The London have struggled to keep track of patient appointments since implementing the Cerner Millennium "Care Records Service" last April. Their difficulties have been compounded by inefficient management information systems.
Last year Barts reported that patients with suspected cancer were not receiving urgent appointments to see specialists within the government's two-week target. The trust said this was "directly attributable to the erroneous migration of outpatient clinics [data] at the change-over to [the] Care Records Service".
For Barts, one challenge has been to attune management processes and train staff to work differently since the introduction of the Care Records Service.
The trust's board says it is of "extreme concern" that Barts has been unable to report on the number of patients who have or have not been treated within 18 weeks of being referred by a GP. The trust is having trouble keeping track on its systems of patients who are due to be treated and by when.
The problems at Barts have hit the performance ratings of London primary care trusts - particularly Tower Hamlets - which pass their patients to Barts for care and treatment.
But the difficulties are not confined to Barts. Several trusts have been trying to return to normal after the introduction of new systems under the £12.7bn National Programme for IT [NPfIT].
The Royal Free Hospital in Hampstead was the first in London to use Release 1 of the Cerner Millennium Care Records Service which requires staff, doctors and nurses to access NPfIT systems by smartcard.
Andrew Way, the then Chief Executive at the Royal Free, told the BBC in February: "I have personally apologised for the decision to implement the system before we were really clear about what we were going to receive. I had been led to believe it would all work."
He said technical problems had cost the trust £10m and meant fewer patients could be seen. "Many of the medical staff are incredibly disappointed with what we have got."
At the British Medical Association's annual representative meeting in London Dr Paul Flynn of the BMA's Central Consultants and Specialists Committee said he had been brought to help doctors at the Royal Free Hospital at Hampstead after the implementation of Cerner Millennium.
"I saw doctors who were enthusiasts for IT turning to complete despair. I have seen doctors almost in tears because of how frustrated they are at being prevented from doing their jobs by the IT system," he said.
Dr Gordon Matthews, a consultant orthopaedic surgeon at Buckinghamshire Hospitals NHS Trust, told the meeting that doctors at his trust were still having difficulties with the Care Records Service system three years after its installation, according to E-Health Insider.
He said: "We are now struggling to install a piecemeal system to run in parallel with CRS [Care Records Service] to provide some clinically useful data."
As a counter to the difficulties with the NPfIT Care Records Service, NHS Connecting for Health is to allow trusts in the south of England to buy hospital patient administration systems from a range of suppliers.
A competition is now being run to choose suppliers under an "Additional Supply Capability and Capacity" framework contract
Barts and The London declined to give Computer Weekly any clear explanation why it had reported in March the largest number of patients in the country who had waited well beyond government time limits for their hospital appointments.
It said: "In March, we reported an unfortunate and significant number of breaches of the 13-week waiting time standard for a first outpatient appointment
"The Trust has contacted those patients to ensure that anyone that still wanted to be seen in outpatients at the Trust was given an appointment during May and June. All patients were treated as a matter of urgency.
"The Trust reported 10 breaches of this standard for May 2009, and there is no evidence from our review that any patient has been harmed by waiting longer than the waiting time standard."
It added: "As we improve our administrative and management systems, patients are able to access our services in a timely manner and therefore fewer of them will breach the waiting time standard."
Barts confirmed that it is "currently not reporting 18-week performance" but " is expecting to begin progressively reporting" it in the coming months.
A spokeswoman for the Department of Health declined to comment on the patients at Barts who waited longer than 13 weeks for appointments. The spokeswoman commented instead on the inability of Barts to report on patients who have, or might not have, been treated within 18 weeks.
She said: ""We should not let the problems at one hospital undermine the fantastic achievement by NHS staff in meeting the 18 weeks commitment nationally five months early."
She added that there is no indication that the "current difficulties that the trust [Barts] is experiencing in reporting, are adding to referral to treatment waiting times or affecting patient care".
Barts' board has "instigated a root and branch review of the trust's waiting list systems to ensure each and every patient's waiting time is accurately recorded".