PRSYS indicates the coding system for the procedures:

• Almost all HCUP inpatient stays use ICD-9-CM procedure codes (PRSYS = 1)
• If Physicians' Current Procedural Terminology (CPT) or HCFA Common Procedure Coding System (HCPCS) procedure codes are indicated (PRSYS = 2 or 3), then the procedure codes are set to missing (PRn = blank). CPT and HCPCS procedure codes could not be retained in the HCUP data because they are 5 characters, and the HCUP procedure fields (PRn) are 4 characters in length.
• If the procedure coding system was not specified by the data source, then PRSYS is missing (PRSYS =l .)

The data element PRSYS was discontinued in 1998.