The SHMI reports on mortality at trust level3 across the NHS in England. It 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 covers all deaths reported of patients who were admitted to non-specialist acute trusts4 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 for5, other underlying conditions the patient suffered from, age, gender and method of admission to hospital).
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 SHMI.
Where a trust has an "as expected" SHMI this means the difference between the number of observed and expected deaths is not statistically significant according to the methodology. A "higher than expected" SHMI should be viewed as a "smoke alarm" which requires further investigation by the trust. Similarly, an "as expected" or "lower than expected" SHMI should not immediately be interpreted as indicating satisfactory or good performance.
The SHMI includes admitted patients for all clinical areas within a trust and it is possible that mortality rates differ across these areas. For this reason, we advise all trusts to investigate their SHMI data in detail using the data broken down by diagnosis group, regardless of whether their SHMI is categorised as "higher than expected", "as expected" or "lower than expected".
The difference between the number of observed deaths and the number of expected deaths cannot be interpreted as the number of avoidable deaths for the trust. Whether or not a death could have been prevented can only be investigated by a detailed case-note review.
Read the full report.
ENDS