Number of deaths per 1,000 spells


Number of deaths per 1,000 spells


Discharges with a method of discharge of death (DISMETH = 4) among cases meeting the inclusion and exclusion rules for the denominator.


All surgical discharges aged 18-90 defined by specific HRGs (Appendix A) with a secondary diagnosis code for potential complications of care (Appendix B).


The admission was either

  • elective (admission method equal to 11, 12 or 13) or
  • an emergency admission (admission method equal to 21, 22, 23, 24 or 28) where the principal operating room procedure took place in <= 2 days of admission.


  • External transfers or unknown transfers (DISDEST = 49-53 but no subsequent spell found) and
  • all non-operating room procedures (Appendix C).

Spells which satisfied the following criteria

Data Source


Time frame

April 2009 - March 2010


Acute Trust

Statistical methods used

  • Case-mix adjusted using a logistic regression model.
  • Logistic regression

The ratio is calculated by dividing the actual number of events by the expected number and multiplying the figure by 100. It is expressed as a relative risk, where a risk rating of 100 represents the national average. If the trust has an RR of 100, that means that the number of events is exactly as it would be expected taking into account the standardisation factors. An RR above 100 means there were more events than would be expected; one below 100 means that fewer than expected events.

Control limits

Control limits tell us the range of values which are consistent with random or chance variation. Data points falling within the control limits are consistent with random or chance variation and are said to display ‘common-cause variation’; for data points falling outside the control limits, chance is an unlikely explanation and hence they are said to display ‘special-cause variation’ - that is, where the trust’s rate diverges significantly from the national rate.


For emergency admissions, the principal operating room procedure date was searched for within the first two episodes of the spell, to check that the procedure took place within two days of the admission date and not just the start of the episode.

Based on AHRQ PSI indicators

Translated by Peter Griffiths and Simon Jones, Kings College London and Alex Bottle from the Dr Foster Unit at Imperial College

Your feedback

Please share any concerns or suggestions for improvement that you might have regarding this indicator. In particular, please consider these questions:

  • Are there any diagnosis or procedure codes that have been included that you believe should be removed? Please give your reasons
  • Are there any diagnosis or procedure codes that have been omitted that you believe should be included? Please give your reasons
  • What are the strengths and weaknesses of this metric as an indicator

You can use the feedback box below to submit comments to HSJ. Alternatively, you can email Dr Foster directly at Please submit your response by 31 August 2010.