The Diagnosis Related Group, Version 24 (DRG24) is assigned by the HCFA DRG Grouper algorithm during HCUP processing. DRG24 is available on the HCUP databases beginning in 2006.

Diagnosis and Procedures Used for DRG Assignment

Beginning in the 1996 data, the DRG grouper can handle a maximum of 50 diagnosis and 50 procedure codes. Only diagnoses and procedure that are valid on the date of discharge are used by the grouper for DRG assignment.

Logically Mapping ICD-9-CM Codes for DRG Version 24

The diagnoses or procedures selected by the above rules are first passed to the 3M Mapper software so that each ICD-9-CM code can be logically translated into codes in effect during fiscal year 2006, the period associated with DRG Version 24. The translated codes are then passed to the DRG Version 24 HCFA Grouper software.

Different Definitions of Diagnosis and Procedure Validity

HCUP validation of diagnosis and procedure codes allows a window of time around the official ICD-9-CM coding changes (usually October 1), for anticipation of or lags in response to official ICD-9-CM coding changes. Beginning in the 1998 data, a year window (six months before and six months after) was allowed.

The DRG Grouper rules differ in two ways:

• diagnosis and procedure codes must be valid on the date of discharge to be used for assigning the DRG; and
• some valid diagnoses (E-codes) are ruled by the DRG Grouper to be invalid if entered as a principal diagnosis.

This inconsistency between the definition of a valid diagnosis or procedure is obvious when a discharge has a valid principal diagnosis under HCUP standards, but the assigned DRG is 470 "Ungroupable."

Labels

Labels for the DRGs are provided as an ASCII file in HCUP Tools: Labels and Formats.

Formats

A format to label DRG24 is documented in HCUP Tools: Variable Labels and Formats.