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Methodology

Hospital Standardised Mortality Ratios

NHS National Services Scotland ISD Scotland & NHS National Services Scotland

Methodology

The Scottish HSMR utilises the routine linkage of data obtained from hospital discharge summaries to death registrations from the National Records of Scotland. The HSMR is calculated for all acute inpatient and day-case patients admitted to all specialties (medical and surgical, excluding obstetrics and psychiatry). The calculation takes account of patients who died within 30 days from hospital admission. This means that the HSMR includes deaths that occurred in the community (out of hospital deaths) as well as those occurring in-hospital. Unlike similar indicators adopted in other parts of the UK, the Scottish HSMR is not a measure of all in-hospital mortality because it does not include patients that die in-hospital after 30-days from admission.

The Scottish HSMR is calculated by obtaining routinely collected death certificate data. These crude mortality data are adjusted to take account of some of the factors known to affect the underlying risk of death. Development of the case-mix adjustment methodology for Scotland began in early 2008. Although the method used in England at that time by Dr Foster informed the Scottish process, the models are different and reflect differences in the source data. Scottish HSMRs are therefore not directly comparable to those produced for English hospitals.

During 2015/16 ISD undertook to fully review the HSMR model methodology and proposed to update it from August 2016. For more information see the Research and Development page. Due to the changes in methodology, HSMRs published from August 2016 onwards cannot be compared to previous releases.

Methodology from August 2016 onwards

A technical document and supporting reference tables are available on how the HSMR is calculated from August 2016 onwards via the links below:

Technical Document 2016 Download PDF file [328 Kb]
Reference Tables Download Excel file [416 Kb]

Methodology prior to August 2016

A technical document Download PDF file [346kb] also remains available on how the HSMR was calculated prior to August 2016.

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