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NASS Description of Data Elements
The Nationwide Ambulatory Surgery Sample (NASS) is a set of ambulatory surgery databases included in the HCUP family. These databases are created by AHRQ through a Federal-State-Industry partnership.
CPTn - CPT-4/HCPCS procedures
Documentation Sections:
General Notes
Uniform Values
General Notes

CPT-4/HCPCS procedures code data elements (CPTn) contain the original values supplied by the data source, except that null values are set to blank. Codes are not validated and the information contained in them is not used for edit checking the consistency of patient's age and sex with procedures.

The original value of the primary CPT-4/HCPCS procedure (CPT1), whether blank or coded, is retained in the first position of the procedure vector. Starting at the first secondary procedure (CPT2), the procedures are shifted during HCUP processing to eliminate blank secondary procedures. For example, if CPT2 and CPT4 contain nonmissing procedures and CPT3 is blank, then the value of CPT4 is shifted into CPT3. Secondary procedures are never shifted into the primary position (CPT1).

Uniform Values
VariableDescriptionValueValue Description
CPTnCPT-4/HCPCS procedures5(a)Procedure code

Internet Citation: HCUP NASS Description of Data Elements. Healthcare Cost and Utilization Project (HCUP). August 2019. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 8/14/19