How well do diagnosis-related group systems group breast cancer surgery patients? Evidence from 10 European countries.

We analysed patient-level data (n = 72,235) from 563 hospitals in 10 European countries to assess the ability of national diagnosis-related group (DRG) systems to account for patient-level variation in cost or lengths of stay of breast cancer surgery patients against a standard set of patient characteristics, treatment and quality variables. We find that European DRG systems use very different types of classification variables and numbers of DRGs (range: 3-7) to classify these patients. In 6 of 10 countries, the set of patient characteristics, treatment and quality variables, which we were able to define across countries, perform better than the set of national DRGs in accounting for patient-level variation in resource consumption. Moreover, there appear to be factors that are consistently significant determinants of cost/length of stay of breast cancer surgery cases but are not, or at least not fully, considered in European DRG systems. Our results therefore raise concerns as to whether all systems rely on the most appropriate classification variables. In several countries, policymakers should reevaluate the appropriateness of their DRG algorithm for breast cancer surgery and of specific DRG weights.