Expansion of Medicare's definition of post-acute care transfers.

In October 1998, the definition of a transfer in Medicare's hospital prospective payment system was expanded to include several post-acute care (PAC) providers in 10 high-volume PAC diagnosis-related groups (DRGs). In this methodological article, the authors respond to a congressional mandate to consider more DRGs in the definition. Empirical results support expansion to many more DRGs that are split in ways that understate total PAC volumes, including 25 DRG pairs (with/without complications) and DRG bundles (e.g., infections) that together exhibit high PAC volumes. By contrast, some DRGs (e.g., craniotomy) are questionable PAC candidates because of their heterogenous procedure mix.