Case-mix adjustment for an expanded renal prospective payment system.

Medicare is considering an expansion of the bundle of dialysis-related services to be paid on a prospective basis. Exploratory models were developed to assess the potential limitations of case-mix adjustment for such an expansion. A broad set of patient characteristics explained 11.8% of the variation in Medicare allowable charges per dialysis session. Although adding recent hematocrit values or prior health care utilization to the model did increase explanatory power, it could also create adverse incentives. Projected gains or losses relative to prevailing fee-for-service payments, assuming no change in practice patterns, were significant for some individual providers. However, systematic gains or losses for different classes of providers were modest.