[The relationship between provider volume and mortality rate: volume data of German centres of excellence].

The purpose of this study was to determine the percentage of centres of excellence (COEs) in Germany that achieved, for selected diagnoses and interventions, annual hospital or surgeon threshold volumes associated with a lower mortality rate. A systematic review and evaluation of the literature identified the most relevant study for each diagnosis and intervention selected. Each diagnosis and intervention was only considered if the most relevant source yielded a threshold volume associated with a reduced mortality rate. COEs received questionnaires on the annual volume of such diagnoses and interventions for each department, providing physician (median), and senior consultant in 1999. For most of the diagnoses and interventions considered, the percentage of COEs meeting their respective threshold volumes exceeded 50%. Exceptions were carotid endarterectomy (performed in departments of general cardiac surgery) and liver transplantation. The percentage of providing physicians and senior consultants performing to the desired standard remained above 75% for most of the diagnoses and interventions. Exceptions were surgeons dealing with carotid endarterectomy, correcting congenital heart disease (both performed in departments of general cardiac surgery), and correcting primary hyperparathyroidism. That a smaller percentage of centres for general cardiac surgery, liver transplantation, and primary hyperparathyroidism operates at their threshold volumes may be due to a relative oversupply of centres specialising in these treatments as well as a the lack of regional centres with a high referral rate. Due to the country-specificity of studies performed on the relationship between volume and mortality rate, it is highly recommended that Germany-specific volume-outcome studies be performed particularly in specialties with relatively low case volumes.