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Central Distributor SID: Description of Data Elements
This section describes how HCUP data elements are coded, restrictions on their use, their uniform values, and State-specific coding practices.
RDRG - Refined DRG
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes

Refined DRGs were developed at Yale University in response to criticism that HCFA DRGs were not appropriate for non-Medicare populations and did not adequately adjust for patient severity. The HCFA DRGs were expanded to better accommodate pediatric and neonate cases, and DRGs for other high cost conditions like trauma and HIV were expanded. All age and complications and comorbidity (CCs) splits of HCFA DRGs were eliminated and replaced by subclasses (Refinement Classes) to indicate severity. Some RDRGs are consistent with HCFA DRGs.

Secondary diagnoses are used to determine complications and comorbidity. The CCs are used to subdivide DRGs into Refinement Classes based upon the highest level secondary diagnosis. Surgical patients are split into the four Refinement Classes. Medical patients are split into three Refinement Classes. The Refinement Class indicates varying levels of impact on patient resource use.

Surgical Refinement Class Medical Refinement Class Description
0 0 Baseline/No substantial CCs
1 1 Moderate CCs
2 2 Major CCs
3 - Catastrophic CCs

The last digit of the RDRG value is the refinement class. The preceding digit(s) are the refined DRG category.

How the RDRG value provided by the data source is stored in the HCUP databases varies by year. - In the 1988-1997 HCUP databases, RDRG is stored in a numeric field which causes leading zeros to be removed. Consider the following examples:

HCUP RDRG Value (1988-97) Refined DRG Category Refinement Class
50 5 0
892 89 2
1821 182 1
  • Beginning in the 1998 data, RDRG is stored in a character field which retains leading zeros. Consider the following examples:
HCUP RDRG Value (Beginning in the 1998 data) Refined DRG Category Refinement Class
0050 5 0
0892 89 2
1821 182 1
Uniform Values
VariableDescriptionValueValue Description
RDRGRefined DRGaaaaRDRG value
State Specific Notes


Source documentation does not indicate which version of the Refined DRG grouper was used.

North Carolina

Source documentation does not indicate which version of the Refined DRG grouper was used.


Beginning in the 1997 data, Oregon supplied the Refined DRG (RDRG). There was no source documentation on which version of the HCFA Grouper was used to assign the RDRGs.

Beginning in 2008, Oregon did not supply RDRG.


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