Clinical Classifications Software (CCS) consists of 231 procedure categories. This system is clinically based on ICD-9-CM codes. All procedure codes are classified.

PRCCS_EDn is coded as follows:

• 1 to 231 if the procedure code (PR_EDn) is valid by the HCUP criteria. The HCUP criteria for procedure validation allows a year window (six months before and six months after) 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.
• PRCCS_EDn is missing (.), if there is no procedure code (PR_EDn = " ").
• PRCCS_EDn is set to invalid (.A), if the procedure code (PR_EDn) is invalid by the HCUP criteria.
• PRCCS_EDn is set to inconsistent (.C), if the procedure code (PR_EDn) is inconsistent with age or sex of the patient.

Labels and formats for CCS categories are provided as an ASCII file in HCUP Tools: Labels and Formats.