Hospital comparisons difficult due to poor data capture - Dr Foster

Figures published in the Dr Foster Hospital Guide 2010 find that NHS hospital trusts reported over 30,500 life-threatening blood clots and 32,300 other adverse medical events, such as obstetric tears and accidental puncture or laceration.

However it is likely the true number is many more. Nine trusts recorded no instances of at least one type of adverse event.

Over 30,500 patients were recorded as having Pulmonary Embolisms (PE), a blood clot on the lung, while in hospital, however the report added: "This is an undercount because many patients with PEs are not coded as such, instead being recorded as having had unspecified complications."

Roger Taylor, director of research at Dr Foster said: "It is concerning that no hospital in the country can accurately assess the level of adverse events compared with the best achievable rates."

He continued: "Dr Foster is asking the Department of Health to review the way this information is recorded and we hope to revisit this topic next year and be able to identify trusts and their rates."

Commenting on the report, Katherine Murphy, chief executive of the Patients Association, said: Patients need meaningful information, delivered in everyday language, so that they can make an informed choice of hospitals and services. However it is essential that the information is accessible, readable and clear. It is not an informed choice if patients are unable to engage or access the information presented to them."

Better news is that over the ten years the Hospital Guide has been published, the wide variation in death rates has narrowed and there is a greater focus on improving clinical outcomes and safety.

Only 19 of the 147 hospitals trusts now have significantly high death rates, compared with 27 last year, while 26 trusts had significantly low rates.

Dr Foster was established ten years ago to "end the official monopoly on data about NHS performance".