Disagreement about the right way of measuring hospitals’ standardised mortality ratios is compromising “confidence in them and their effective use”, the NHS Information Centre has warned.

It plans to set a fixed method and tender the contract to provide results for the NHS Choices website.

The results do have a correlation but you don’t always get the same result

The measure, created by Sir Brian Jarman at Imperial College, has been used since 2001 and continues to be developed by Imperial’s Dr Foster Unit, which Sir Brian heads.

The unit is funded by Dr Foster Intelligence, a joint venture between the Information Centre and health information company Dr Foster.

The measure was given a higher profile by the scandal at Mid Staffordshire Foundation Trust, where mortality ratios helped alert the Healthcare Commission to poor care. Since April hospitals’ results have been published on NHS Choices.

However, other companies have been providing hospitals with mortality ratios calculated in a different way.

The Information Centre announced in a statement earlier this month: “The NHS next stage review highlighted the use of clinical indicators, such as hospital standardised mortality ratios, as useful tools.

“However, confidence in them and their effective use is complicated by the fact that different ways of measuring mortality ratios are used across the NHS.”

It has commissioned an assessment of methodology for the ratios and other clinical measures, and will soon invite providers to tender “for the production of clinical indicators” for NHS Choices.

The agreed methodologies “should become the NHS standard”, the Information Centre said.

Paul Robinson, head of market intelligence at healthcare information firm CHKS, which was bought by outsourcing specialist Capita in February, said: “There are several ways of calculating the ratios, of which one is ours. The results do have a correlation but you don’t always get the same result.” Capita took over the contract to run NHS Choices from Dr Foster Intelligence last year.

A spokesman for Dr Foster said it did not want to comment before the tender was published.