The Dutch Hospital Standardized Mortality Ratio (HSMR) Method and Cardiac Surgery: Benchmarking in a National Cohort Using Hospital Administration Data Versus a Clinical Database

Study Questions:

How accurate are data from hospital administration databases and a national clinical cardiac surgery database? And, what is the comparative performance of the Dutch hospital standardized mortality ratio (HSMR) method and the logistic European System for Cardiac Operative Risk Evaluation, for the purpose of benchmarking of mortality across hospitals?


Information on all patients undergoing cardiac surgery between 2007-2010 in 10 centers was extracted from The Netherlands Association for Cardio-Thoracic Surgery database and the Hospital Discharge Registry. The number of cardiac surgery interventions was compared between both databases. The European System for Cardiac Operative Risk Evaluation and hospital standardized mortality ratio models were updated in the study population and compared using the C-statistic, calibration plots, and the Brier Score.


The number of cardiac surgery interventions performed could not be correctly assessed using the administrative database. The intervention code was incorrect in 1.4-26.3%, depending on the type of intervention, and in 7.3%, no intervention code was registered. The updated administrative model was inferior to the updated clinical model with respect to discrimination (c-statistic of 0.77 vs. 0.85, p < 0.001) and calibration (Brier Score of 2.8% vs. 2.6%, p < 0.001, maximum score 3.0%). Two average performing hospitals according to the clinical model became outliers when benchmarking was performed using the administrative model.


The authors concluded that administrative databases are less suitable than clinical databases for risk adjustment.


This study highlights the challenges associated with use of administrative databases. Administrative data are commonly used to rank hospital quality and are currently being used for public reporting of outcomes, as well as for pay for performance. The results of this study corroborate prior work (see Hannan et al., Health Serv Res 1997;31:659-78) and argue for a switch from administrative to clinical databases for these purposes.

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