The appropriateness of using hospital standardised mortality ratios to judge hospital performance was further questioned this week.

Birmingham University professor of clinical epidemiology Richard Lilford  and Peter Pronovost, a critical care and patient safety specialist at Johns Hopkins University school of medicine in Baltimore, argue the figures are “a poor diagnostic test for quality” and “should not be used to calculate excess deaths resulting from poor care”.

They say quality should be measured instead on the basis of selected outcomes – such as blood stream infection rates. They also endorse the health select committee’s recommendation that selected patient care notes should be audited to see if the correct treatment was given.

In an accompanying article in the BMJ this week Nick Black, professor of health services research at London School of Hygiene and Tropical Medicine, argues the ratios should be “abandoned”, as they are “not fit for purpose”. He also argues that more specialised measures should be used instead.

The BMJ article comes as healthcare information provider CHKS also publishes research which it says “casts doubt on the stability and uniformity of the data set [used to calculate the ratios] and thereby asks major questions of their suitability for inter-hospital comparisons”.

It says several hospitals whose ratios have reduced have not seen a significant fall in deaths, suggesting the change does not reflect improved care. CHKS will present the work to the Department of Health’s mortality ratios review group, set up to agree a standard methodology and approach.

But the value of the measure has been vigorously defended by other specialists, including Imperial College London emeritus professor Sir Brian Jarman,  who developed it and championed its use. It was credited with helping to identify failures at Mid Staffordshire Foundation Trust.