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Avoidability of hospital deaths and association with hospital-wide mortality ratios: retrospective case record review and regression analysis

BMJ 2015; 351 doi: (Published 14 July 2015) Cite this as: BMJ 2015;351:h3239
  1. Helen Hogan, senior lecturer in public health1,
  2. Rebecca Zipfel, research fellow1,
  3. Jenny Neuburger, lecturer in statistics1,
  4. Andrew Hutchings, lecturer in health services research1,
  5. Ara Darzi, professor of surgery2,
  6. Nick Black, professor of health services research1
  1. 1Department of Health Services Research & Policy, London School of Hygiene & Tropical Medicine, London WC1H 9SH, UK
  2. 2Department of Surgery & Cancer, St Mary’s Campus, Imperial College, London, UK
  1. Correspondence to: H Hogan Helen.Hogan{at}
  • Accepted 30 May 2015


Objectives To determine the proportion of avoidable deaths (due to acts of omission and commission) in acute hospital trusts in England and to determine the association with the trust’s hospital-wide standardised mortality ratio assessed using the two commonly used methods - the hospital standardised mortality ratio (HSMR) and the summary hospital level mortality indicator (SHMI).

Design Retrospective case record review of deaths.

Setting 34 English acute hospital trusts (10 in 2009 and 24 in 2012/13) randomly selected from across the spectrum of HSMR.

Main outcome measures Avoidable death, defined as those with at least a 50% probability of avoidability in view of trained medical reviewers. Association of avoidable death proportion with the HSMR and the SHMI assessed using regression coefficients, to estimate the increase in avoidable death proportion for a one standard deviation increase in standardised mortality ratio.

Participants 100 randomly selected hospital deaths from each trust.

Results The proportion of avoidable deaths was 3.6% (95% confidence interval 3.0% to 4.3%). It was lower in 2012/13 (3.0%, 2.4% to 3.7%) than in 2009 (5.2%, 3.8% to 6.6%). This difference is subject to several factors, including reviewers’ greater awareness in 2012/13 of orders not to resuscitate, patients being perceived as sicker on admission, minor differences in review form questions, and cultural changes that might have discouraged reviewers from criticising other clinicians. There was a small but statistically non-significant association between HSMR and the proportion of avoidable deaths (regression coefficient 0.3, 95% confidence interval −0.2 to 0.7). The regression coefficient was similar for both time periods (0.1 and 0.3). This implies that a difference in HSMR of between 105 and 115 would be associated with an increase of only 0.3% (95% confidence interval −0.2% to 0.7%) in the proportion of avoidable deaths. A similar weak non-significant association was observed for SHMI (regression coefficient 0.3, 95% confidence interval −0.3 to 1.0).

Conclusions 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 lack of association between the proportion of avoidable deaths and hospital-wide SMRs partly reflects methodological shortcomings in both metrics. Instead, reviews of individual deaths should focus on identifying ways of improving the quality of care, whereas the use of standardised mortality ratios should be restricted to assessing the quality of care for conditions with high case fatality for which good quality clinical data exist.


  • We thank the staff of the 34 trusts for participating and supporting the case record reviewing; the clinicians for reviewing the records; Mike Campbell for providing summary hospital level mortality indicator data for 2009; and Frances Healey, Graham Neale, Richard Thomson, Charles Vincent, and three peer reviewers for providing valuable advice and comments.

  • Contributors: HH and NB designed the study. RZ managed data collection. HH, RZ, JN, and AH conducted the analyses. HH and NB drafted the paper. JN, AH, and AD contributed to interpreting the data and drafting. HH is the guarantor. She had full access to all data in the study and had final responsibility for the decision to submit for publication.

  • Funding: The 2009 phase of this study was funded by the National Institute of Health Research, research for patient benefit programme (PB-PG-1207-15215) and the 2012/13 phase by the Department of Health policy research programme. The views expressed in this paper are those of the authors and not necessarily those of the funding bodies. The funders of the study, DH PRP and NIHR had no role in the study design; data collection, analysis, and interpretation; or composition of the report. The views expressed in this publication are those of the authors and not necessarily those of the NHS or the Department of Health.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the NRES Committee London-Central. Research governance approval was granted by each participating trust.

  • Data sharing: No additional data available.

  • Transparency: The lead author (HH) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained.

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