The SHMI is the ratio between the actual number of patients who die following hospitalisation at the trust and the number that would be expected to die on the basis of average England figures, given the characteristics of the patients treated there. It includes deaths which occurred in hospital and deaths which occurred outside of hospital within 30 days (inclusive) of discharge.
The SHMI gives an indication for each non-specialist acute NHS trust in England whether the observed number of deaths within 30 days of discharge from hospital was 'higher than expected' (SHMI banding=1), 'as expected' (SHMI banding=2) or 'lower than expected' (SHMI banding=3) when compared to the national baseline.
Trusts may be located at multiple sites and may be responsible for one or more hospitals. A breakdown of the data by site of treatment is also provided.
The SHMI is composed of 142 different diagnosis groups and these are aggregated to calculate the overall SHMI value for each trust. The number of finished provider spells, observed deaths and expected deaths at diagnosis group level for each trust is available in the SHMI diagnosis group breakdown files. For a subset of diagnosis groups, an indication of whether the observed number of deaths within 30 days of discharge from hospital was 'higher than expected', 'as expected' or 'lower than expected' when compared to the national baseline is also provided.
Details of the 142 diagnosis groups can be found in Appendix A of the SHMI specification.
1. There is a large shortfall in the number of records for Salford Royal NHS Foundation Trust (trust code RM3) meaning that values for this trust will be based on incomplete data and should therefore be interpreted with caution. This shortfall will be corrected for future SHMI publications.
2. There have been some methodological changes to the SHMI from the May 2019 publication onwards, including changes to the diagnosis groups used in the calculation of the indicator, the inclusion of an adjustment for seasonality and the inclusion of an adjustment for birthweight in the statistical models for the perinatal diagnosis groups (groups 115-119 and 141). Further information is available in the statement of methodological changes, which can be accessed from the publication page.
3. Further information on data quality can be found in the SHMI background quality report, which can be downloaded from the 'Resources' section of the publication page.