The Dr Foster Unit at Imperial College is making four methodological upgrades to the Hospital Standardised Mortality Ratio (HSMR) risk models to improve case-mix adjustment and make the methodology more statistically robust. The four changes are:
1. Only use data from 2000/2001 onwards
As we now have 15 years of data, and the early years are of lesser quality, and perhaps reflect different patterns of care, we are only going to use the most recent years of better quality data from 2000/01 onwards.
2. Remove ethnicity from the case-mix model
Although coding is improving, ethnicity is variably recorded across trusts. In some cases, up to 50% of admissions record ethnicity as unknown and this unequal recording may be very slightly biasing some of our indicators. We are therefore going to remove it from the case-mix model (although you will still be able to analyse by ethnicity in our quality solution, Real Time Monitoring).
3. Improved Charlson weightings for interaction
The effect of comorbidity differs by age. We are now taking this into account in our case-mix model. The inclusion of interaction terms is widely used in the literature.
4. Better adjustment for age
Where previously the HSMR model required at least 20 deaths per age group we now only need 10 deaths per group. This better adjustment for age will give us a better prediction of death for each patient.
What does this mean?
The improvements to the methodology mean greater power in the modelling for most diagnoses within Dr Foster’s Real Time Monitoring tool, strengthening the insight that can be gleaned by users from the drill-down capabilities. These upgrades are fundamentally about improving the underlying models that compose the HSMR.
This also means that all English HSMR’s will change slightly to reflect the impact of the new risk model. Early estimates show that For 2010/11, three trusts will improve banding, one trust will go from ‘as expected’ to ‘higher than expected’ and that all other acute hospital trusts will stay within the same band. Your regional Customer Support Managers will be in touch directly if you are affected by a change in band.
Differences in HSMR’s are likely to range from – 4.3 points to + 2.7 points. However, for 65% of trusts the difference will be ± 1 point or lower, for 84% of trusts the difference will be ± 1.5 points or lower and for 95% of trusts the difference will be ± 2 points or lower. Therefore only 5% of trusts will have a difference in their HSMR of greater than ± 2 points.
The data extract will be published in early September and will be used to calculate 2010/2011 HSMRs and other indicators for the 2011 Hospital Guide.
Should you have any questions please contact your regional Customer Support Manager (CSM) for more information. If you do not know who your CSM is please call 0800 288 9810.