Hospital mortality – what does it tell us?

Hospital Mortality Graph size 300

Mike Campbell in DTS has been involved in a number of projects involving deaths in hospital. He recently (March 2015) gave a talk to the Sheffield Festival of Science on the topic.

The research started when he won some funding from the Department of Health to develop the Summary Hospital Mortality Index (SHMI).  The team comprised himself, Richard Jacques (DTS) , James Fotheringham (DTS), Jon Nicholl (HSR) and Ravi Maheswaran (PH).

Campbell MJ, Jacques RM, Fotheringham J, Maheswaran R, Nicholl J (2012) Developing a summary hospital mortality index: retrospective analysis in English hospitals over five years. BMJ doi 10.1136/bmj.e1001

This Index is an alternative to the Hospital Mortality Standardised Rate (HMSR) produced by the commercial company Dr Foster to monitor whether hospitals have excess mortality, and which identified Mid-Staffordshire hospital’s poor care. The SHMI is now used by the Department of Health to monitor hospitals and was used by Sir Bruce Keogh to investigate 14 hospitals for further investigations in 2013.

This work was followed up by noticing that hospital mortality in England and Wales is in fact falling from 2005-10. As measured by the SHMI there has been a 24% improvement in mortality in acute general trusts in
England over a period of five and a half years. Part of this improvement is an artificial effect caused by changes in the depth of coding of comorbidities and other effects due to change in case-mix or non-constant risk but part may be due to improvements in care.

Jacques RM, Fotheringham J, Campbell MJ, Nicholl JP (2013) Did hospital mortality in England change from 2005 to 2010? A retrospective cohort analysis. BMC Health Services Research, 13, 216 DOI 10.1186/1472-6963-13-216

However, it is not clear, even after allowing for factors that a hospital cannot influence, such as how ill patients are when they come to hospital, that mortality is a good measure of quality of care. This was reviewed in a recent paper.

Goodacre S, Campbell M, Carter A (2015) What do hospital mortality rates tell us about quality of care? Emergency Medical Journal 32:244-247 doi:10.1136/emermed-2013-203022 doi: 10.1136/emermed-2013-203022

We found that studies exploring whether variation in risk-adjusted mortality can be explained by variation in healthcare have reached conflicting conclusions. Concerns have been raised that the proportion of preventable deaths among hospital admissions is too small to produce a reliable ‘signal’ in risk-adjusted mortality rates. This provides hospital managers, regulators and clinicians with a considerable dilemma. Variation in mortality rates cannot be ignored, as they might indicate unacceptable variation in healthcare and avoidable mortality, but they also cannot be reliably used to judge the quality of healthcare, based on current evidence.