Intended for healthcare professionals


Patient safety indicators for England from hospital administrative data: case-control analysis and comparison with US data

BMJ 2008; 337 doi: (Published 17 October 2008) Cite this as: BMJ 2008;337:a1702
  1. Veena S Raleigh, fellow in information policy1, reader, postgraduate medical school2,
  2. Jeremy Cooper, analyst programmer1,
  3. Stephen A Bremner, statistician1,
  4. Sarah Scobie, head of analysis and feedback unit3
  1. 1Healthcare Commission, London EC1Y 8TG
  2. 2University of Surrey, Guildford, Surrey GU2 7WG
  3. 3National Patient Safety Agency, London W1T 5HD
  1. Correspondence to: V S Raleigh veena.raleigh{at}
  • Accepted 2 August 2008


Objective To assess the feasibility of deriving patient safety indicators for England from routine hospital data and whether they can indicate adverse outcomes for patients.

Design Nine patient safety indicators developed by the United States Agency for Healthcare Research and Quality (AHRQ) were derived using hospital episode statistics for England for 2003-4, 2004-5, and 2005-6. A case-control analysis was undertaken to compare length of stay and mortality between cases (patients experiencing the particular safety event measured by an indicator) and controls matched for age, sex, health resource group (standard groupings of clinically similar treatments that use similar levels of healthcare resource), main specialty, and trust. Comparisons were undertaken with US data.

Setting All NHS trusts in England.

Participants Inpatients in NHS trusts.

Results There was fair consistency in national rates for the nine indicators across three years. For all but one indicator, hospital stays were longer in cases than in matched controls (range 0.2-17.1 days, P<0.001). Mortality in cases was also higher than in controls (5.7-27.1%, P<0.001), except for the obstetric trauma indicators. Excess length of stay and mortality in cases was greatest for postoperative hip fracture and sepsis. England’s rates were lower than US rates for these indicators. Increased length of stay in cases was generally greater in England than in the US. Excess mortality was also higher in England than in the US, except for the obstetric trauma indicators where there were few deaths in both countries. Differences between England and the US in excess length of stay and mortality were most marked for postoperative hip fracture.

Conclusions Hospital administrative data provide a potentially useful low burden, low cost source of information on safety events. Indicators can be derived with English data and show that cases have poorer outcomes than matched controls. These data therefore have potential for monitoring safety events. Further validation, for example, of individual cases, is needed and levels of event recording need to improve. Differences between England and the US might reflect differences in the depth of event coding and in health systems and patterns of healthcare provision.


  • We thank Richard Thomson, Adrian Cook, Jessica Chamberlain, Emma Hawe, and Ann Petruckevitch for their contribution to developing the analyses in the early stages; Frances Murphy for her expertise in translating ICD-9 to ICD-10 and OPCS procedure codes; and the Dr Foster Unit at Imperial College for collaborating on the translation of the indicators, which they did in parallel to us. There have been subsequent modifications to the codes, by them and us, which might account for some differences in rates.

  • Contributors: VSR and SS conceived and designed the study and the overall analysis plan. JC developed the coding schema and analysed the data. SAB undertook the matched case-control analysis. All authors contributed to drafting the paper and approving its submission for publication. VSR is guarantor.

  • Funding: The Healthcare Commission received a small grant from the Health and Social Care Information Centre to support the initial recoding work.

  • Competing interest: None declared.

  • Ethics approval: Not required.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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