NASS Database Documentation

The largest all-payer ambulatory surgery database in the United States, the Nationwide Ambulatory Surgery Sample (NASS) produces national estimates of major ambulatory surgery encounters in hospital-owned facilities. The NASS contains clinical and resource-use information that is included in a typical hospital-owned facility record, including patient characteristics, clinical diagnostic and surgical procedure codes, disposition of patients, total charges, expected source of payment, and facility characteristics.

The links below provide detailed documentation for the NASS, from a high-level overview to all the detailed specifications, restrictions, and resources necessary for researchers working and publishing with the NASS.
Description of NASS Database Restrictions on Use File Specifications and Load Programs
Data Elements
Additional Resources for Data Elements
  • HCUP Quality Control Procedures (PDF file, 532 KB; HTML)
  • HCUP Coding Practices (PDF file, 171 KB; HTML)
  • HCUP Hospital Identifiers (PDF file, 174 KB; HTML)
  ICD-10-CM Data Included in the NASS HCUP Tools: Labels and Formats Obtaining HCUP Data

Internet Citation: NASS Database Documentation. Healthcare Cost and Utilization Project (HCUP). May 2020. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 5/12/20