NHS chiefs have called for a probe into the 'death rate' at Buckinghamshire's hospitals, after a new indicator showed it may be "higher than expected".

Thirty-six hospital trusts were identified with a 'high' death rate on one measure, which the Department of Health said could reflect underlying problems in the quality of care.

However, two bandings of the “experimental” Summary Hospital-level Mortality Indicator (SHMI) have been published, with Bucks said to be “as expected” on the other measure.

This second banding was adjusted for uncertainties in an attempt to ensure greater accuracy and resulted in a “higher than expected” rate for just 14 trusts. The need for investigation in these cases is stronger.

Health Secretary Andrew Lansley said of the overall SHMI: "This new measure will help ensure patient safety by acting like a smoke alarm to prompt further investigation.

“Alongside other data, this will help the NHS in future to spot and act on poor care as soon as possible.”

In 2010/11 there were 1,667 deaths observed at Buckinghamshire Healthcare NHS Trust (BHT), which runs Wycombe, Stoke Mandeville and Amersham hospitals, against an expected number of 1,491.

The SHMI, which also monitors deaths occurring within 30 days of discharge, has been brought in to offer a “more comprehensive picture” than the previous measure, called the Hospital Standardised Mortality Ratio (HSMR).

The HSMR had identified BHT as having one of the highest death rates in England, but bosses said its data had not been accurate.

Lee Jones, spokesman for the Bucks hospitals, said: “We have worked hard to improve the way we record mortality data and are pleased to see this has been recognised in the new SHMI.

“Whilst not complacent, we are pleased that we have seen an improvement in our mortality ratio and we are assured through clinical review that our underlying mortality rates are not high. We know there is more we can do and we continue to work hard to monitor and improve our SHMI.”