The SHMI reports on mortality at trust level across the NHS in England. Methodological changes will be made from today’s publication.
The SHMI is the ratio between the actual number of patients who die following hospitalisation, and the number that would be expected to die on the basis of average England figures.
The SHMI can be used by hospital trusts to compare their mortality outcomes to the national baseline. However, it should not be used to directly compare mortality outcomes between trusts and it is inappropriate to rank trusts according to their SHMI2.
It covers all deaths reported of patients who were admitted to non-specialist acute trusts3 in England and either die while in hospital or within 30 days of discharge.
The expected number of deaths is calculated from statistical models derived to estimate the risk of mortality based on the characteristics of the patients, including the condition the patient was in hospital for4, other underlying conditions the patient suffered from, age, gender, method and month of admission to hospital, and birthweight (for perinatal diagnosis groups only).
Changes to the SHMI
From the May 2019 publication onwards, a breakdown of the data by site of treatment will be available alongside the trust level results. This new breakdown is being published as an experimental statistic5.
All output counts will now be rounded to the nearest five, with the underlying SHMI values calculated from the unrounded values. This is to ensure consistency with the Hospital Episode Statistics disclosure control methodology6.
The SHMI is now composed of 142 different diagnosis groups which are aggregated to calculate the overall SHMI value for each trust. The increase from 140 diagnosis groups has been made to improve the accuracy of the indicator7.
Also from May 2019, the SHMI will be published on a monthly basis rather than every quarter. Each publication will include discharges in a rolling twelve-month period.
Full details of all the updates are available in the methodological changes document which is available to download from https://digital.nhs.uk/data-and-information/find-data-and-publications/statement-of-administrative-sources/methodological-changes#indicators.
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Notes to editors
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- Further information on how to interpret the SHMI is available to download from the SHMI homepage at https://digital.nhs.uk/data-and-information/publications/ci-hub/summary-hospital-level-mortality-indicator-shmi.
- Specialist trusts, mental health trusts, community trusts and independent sector providers are excluded from the SHMI because there are important differences in the case-mix of patients treated there compared to non-specialist acute trusts and the SHMI has not been designed for these types of trusts. Integrated trusts which provide both acute and community services are included in the SHMI.
- No adjustment is made for the severity of the condition as this information is not captured in the Hospital Episode Statistics (HES) dataset upon which the SHMI is based. This means that if a trust treats a high (or low) proportion of seriously ill patients with a particular condition compared to other trusts, the statistical models used to estimate the expected number of deaths will not take account of this.
- Experimental statistics are official statistics which are published in order to involve users and stakeholders in their development at an early stage.
- Full details of the updated HES disclosure control methodology are available to download from https://digital.nhs.uk/data-and-information/find-data-and-publications/statement-of-administrative-sources/methodological-changes#hospital-care.
- Further details of the SHMI diagnosis groups are available in the methodology specification document which is available to download from the SHMI homepage at https://digital.nhs.uk/data-and-information/publications/ci-hub/summary-hospital-level-mortality-indicator-shmi.
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