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Central Distributor SID: Description of Data Elements

ADRG - All Patient Refined DRG
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes

All Patient Refined DRGs (APR-DRGs) are a DRG refinement developed by 3M Health Information Services to improve upon the Refined DRGs developed at Yale University. They were enhanced by incorporating additional pediatric DRG modifications, recognizing the impact of multiple Complications and Comorbidities (CCs), and refined CC definitions. The APR-DRGs eliminated the HCFA DRG splits for CCs and death, and all but two of the age splits and replaced them with complexity subclasses.

Except for newborn DRGs, each patient is assigned to a complexity subclass (HCUP data element ADRGSEV). Assignment to a complexity subclass is based, in part, on the complexity of a patient's secondary diagnoses, interactions among secondary diagnoses, age, principle diagnosis, and the presence of certain nonoperating room procedures.

APR-DRG codes are supplied by the data source. During HCUP processing, source values are maintained as reported. The two-digit APR MDC code is stored in the data element AMDC. The three-digit APR DRG code is stored in the data element ADRG. The one-digit complexity subclass is stored in ADRGSEV. The one-digit risk of mortality class is stored in ADRGRiskMortality beginning in the 1998 data and ADRGRMS in the earlier years.

Note to analysts: this data element may not be uniformly coded across states because it is assigned by the data source. Please refer to the state-specific notes below about the version of software used for a particular state.

For more information see "All Patient Refined Diagnosis Related Groups (APR-DRGs)," published by 3M Health Information Services.

Uniform Values
VariableDescriptionValueValue Description
ADRGAll Patient Refined DRGnnnAPR-DRG
. or 0Missing
State Specific Notes


Source documentation does not include which version of the APR-DRG grouper was used.


For Maine only, the ADRG and AMDC data elements contain the 3M All Patient DRG and MDC rather than the 3M All Patient Refined DRG and MDC. Source documentation indicates that the current version of the All Patient DRG (ADRG) is applied to the data.


For 2018 - Q4 and 2019 Q1-Q3, the APR-DRGs were incorrectly assigned for infants under the age of 1 year admitted after the date of birth and that had no birth weight reported.

Beginning 2016, Massachusetts provides the 3M Health Information Systems All Patient Refined (APR) DRG grouper Version 34.0.

From 2014 through 2015, Massachusetts provides the APR-DRG Version 30.0.

From 2009 through 2013, Massachusetts provides the APR-DRG Version 26.1 grouper to assign ADRG.

From October 2006 through September 2008, Massachusetts used the Version 20 grouper to assign ADRG. Beginning in October 2008, Massachusetts no longer provided the Version 20 grouper to assign ADRG. From October 1999 through September 2006, Massachusetts used Version 15. Prior to that, Massachusetts used the Version 12 grouper to assign ADRG.


Michigan provides the All Patient Refined DRG.


Source documentation does not include which version of the APR-DRG grouper was used.


Prior to April 1998, ADRG is assigned using Version 12.0. Starting in April 1998, Utah uses Version 15.0. Source documentation indicates that there is a significant difference between version 12.0 and version 15.0.


Internet Citation: HCUP Central Distributor SID Description of Data Elements - All States. Healthcare Cost and Utilization Project (HCUP). August 2008. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 8/12/08