The reputation of the NHS for securely holding information has suffered a further blow after the loss of another 4,000 medical and personal details came to light on Friday.
Stockport Primary Care Trust (PCT) admitted it had not informed the thousands affected after it lost their names, dates of birth and details of medical conditions in December.
The details, which also included NHS numbers and details of GPs, was on a USB drive that was dropped by an employee.
The lapse comes in the wake of the loss of hundreds of thousands of patients' records by nine NHS trusts in December.
Stockport PCT said it had searched for the missing drive but it had not been found, adding that local GPs and the Department of Health have been informed.
The chief executive of Stockport PCT, Richard Popplewell, said in a statement that the drive did not have a protective cover and had been dropped on a road during a rainy day.
Popplewell said: "It is extremely likely that the data was lost in circumstances in which it would be unrecoverable."
"We did not notify the patients affected because the data lost would not be of assistance to ID fraudsters," Popplewell added.
The details related to patients with long-term conditions, such as asthma and diabetes.
A spokesman for the trust said: "Steps have been taken to emphasise to staff safety when carrying personalised data, and there is a full review still taking place of the incident."
The latest loss follows news that Oldham PCT has also lost two USB sticks containing the personal and care-assessment details of 148 patients.
Oldham PCT is also reviewing its data-security procedures following its loss of data — including names, addresses and dates of birth — and is contacting patients affected.