2. Method changes

This chapter summarizes the changes in the HSMR method (HSMR 2024) compared to the method used last year (HSMR 2023). For previous changes see the respective methodological reports (CBS, 2011, …, 2024). Overall, the method has remained the same. Several small changes were implemented and are described below. These changes are applied to all years of the present reporting period (2022-2024).

• The covariate ‘month of admission’ of the COVID-19 model was the same as for the models of other diagnosis groups, consisting of two-month categories (see section 3.4). It was no longer necessary to use the more detailed ‘month of admission’ variable that was used in the previous COVID-19 model.
• Hospital admissions that were fully (i.e. for the whole duration of the admission) registered at a rehabilitation or psychiatry unit were excluded from the population of admissions that was used to calculate the HSMR (see section 3.1.2).
• Finally, a small change in the method of calculating the national average of the indicators used for data quality and case mix presented in the individual hospital reports has been implemented. Instead of calculating a mean over all hospital means, the mean is calculated over all admissions (resulting in a smaller weight for smaller hospitals) from 2024 onwards.