The All Patient Refined DRGs (APR-DRGs) are assigned using software developed by 3M Health Information Systems. This severity measure includes the base APR-DRG, the severity of illness subclass, and the risk of mortality subclass within each base APR-DRG. The prefix "APRDRG" has been included in the data element names to distinguish APR-DRG measures from other HCUP data elements. For more information, please refer to the following documents available on the NIS Documentation CD-ROM and on the HCUP User Support Website (www.hcup-us.ahrq.gov):

• Overview of Severity Systems
• APR-DRGs V20 Methodology Booklet