Avoidable deaths measure condemned
The way avoidable deaths are measured in hospitals is "distracting and potentially misleading" and should not be used to assess quality of care, experts have said.
The proportion of avoidable deaths is currently measured using two commonly-used methods - the hospital standardised mortality ratio (HSMR) and the summary hospital level mortality indicator (SHMI).
But a study, carried out by a team from the London School of Hygiene and Tropical Medicine and Imperial College London, concluded that the small proportion of deaths judged to be avoidable means that detecting any significant differences between trusts is unlikely.
They said this means it is not possible to reflect the true quality of a hospital and instead, reviews of individual deaths should focus on identifying ways of improving care rather than penalising hospitals.
Their study, which is published in the BMJ, said that overall standardised mortality ratio (SMR) for all deaths in a hospital has been used to indicate the quality of the institution for more than 20 years, despite concerns being raised about the method in the past.
A review, overseen by NHS England medical director Sir Bruce Keogh in the wake of the Mid Staffs scandal, aimed to analyse the quality of care and treatment provided by 14 NHS trusts that had a higher than expected SMR for two consecutive years and led 11 of them to be placed into special measures.
This team enlarged this study to look at 3,400 deaths at 34 randomly selected trusts, making it the largest nationally representative case record review of hospital deaths in England.
They enlisted the help of experienced doctors who reviewed all aspects of patients' care and the proportion of deaths they judged likely to have been avoidable was compared with the trust's HSMR and SHMI.
Researchers found t he proportion of avoidable deaths was 3.6% and said "o nly weak positive associations" were observed between the proportion of avoidable deaths in a trust and HSMR or SHMI, "neither reaching statistical significance".
"The small proportion of deaths judged to be avoidable means that any metric based on mortality is unlikely to reflect the quality of a hospital," the team said.
"Even if a larger sampl e of trusts and cases was taken, it would be unlikely to reveal a clinically important association, even if it achieved statistical significance.
" Thus, hospital-wide SMRs do not provide a useful indication of the proportion of avoidable deaths in a trust."
Lead author Dr Helen Hogan, senior lecturer in public health at the London School of Hygiene & Tropical Medicine, said: "Our findings suggest that the commonly used hospital-wide SMRs are not a useful reflection of the proportion of avoidable deaths in a trust.
"Dreadful though each avoidable hospital death is, they are too infrequent to be the basis of a robust indicator to detect significant differences between trusts. There are credible alternatives for assessing the quality of hospitals which give a fairer and more accurate picture."
Study senior author, Nick Black - professor of health services research at the London School of Hygiene & Tropical Medicine, said: "Hospital-wide SMRs can be distracting and potentially misleading and should not be used as a basis to praise or condemn a hospital or trust.
"We need to support and help hospitals to raise standards, not criticise and punish them."
Professor Sir Mike Richards, chief inspector of hospitals at the Care Quality Commission, said he welcomed the "important study".
"Having a clear understanding of the circumstances around avoidable patient deaths in hospitals is of paramount importance," he added.
"We encourage hospitals to review the records of people who have died while in their care, to see if any lessons can be learnt from any that could have been prevented.
"By reviewing a range of intelligence and by carrying out inspections, we can look in detail about the quality and safety of care that hospitals are providing.
"I agree with the study authors that looking at mortality rates in isolation will not give a full picture of quality. This is why we look at a range of measures during every inspection, including talking to staff and patients, to assess if a trust is providing safe and effective care."