Cases of hospital superbug MRSA were poorly recorded

The National Patient Safety Agency estimates one in 10 patients admitted to NHS hospitals is harmed, to some degree, as a result of their care.

But independent research group Dr Foster found some trusts reported no mistakes, which it says is an unlikely claim.

The NPSA says it is addressing the issue of under-reporting of errors.

The appropriate level of attention is simply not given to solve this problem Roger Taylor of Dr Foster

Dr Foster analysed four years of statistics from 1999-2000 to 2002-03, amounting to 50,215,687 episodes of care - a period of care under one particular doctor.

The researchers looked at the number of adverse events - unintended harm to the patient caused by medical management rather than their illness, resulting in death, life-threatening illness, disability, hospitalisation or prolonged stay in hospital.

Scale of problem

They found that on average 2.2% of all episodes, about 27,500 a year, included some kind of adverse event.

Events were more likely in men, the elderly and emergency patients.

The rate of adverse event recording varied between trusts with some reporting no adverse events at all.

Hospital-acquired infections such as the MRSA superbug were also poorly recorded.

The researchers said there was no specific code to indicate a case of MRSA had occurred.

Roger Taylor, of Dr Foster told the BBC: "Throughout the healthcare system these kind of errors are a very large cause of unnecessary death, disability or illness.

"This problem will never be properly tackled until we understand where it's happening, why, and design systems to prevent this taking place."

Reporting flawed

Mr Taylor said: "Some hospitals report no errors and some report as many as 15%.

"The appropriate level of attention is simply not given to solve this problem," he said.

The National Patient Safety Agency (NPSA) welcomed the study and its reporting recommendations.

"It has long been understood that these incidents are under reported, not just here in the UK but worldwide, making it all the more important that information is gathered from a variety of sources," said a spokeswoman.

She said the NPSA was developing systems to improve reporting of medical errors.

It has already developed a National Reporting and Learning System (NRLS) to enable NHS staff to anonymously report errors.

"The NPSA is also setting up a Patient Safety Observatory which will draw together patient safety information from different sources, including the NRLS and studies such as this one from Dr Foster, to maximise our understanding and direct our safety solutions work," she said.

Professor Aidan Halligan, Deputy Chief Medical Officer, said: "Over a million people are treated safely and successfully in the NHS each day.

"While it is an inescapable fact of life that people make mistakes, there is much we can do to reduce their impact and so reduce risks for patients.