User Support

Do Your own analysis
Explore Expert Research & Limited Datasets

NASS Database Documentation

Nationwide Ambulatory Surgery Sample (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, 1.1 MB)
  • HCUP Coding Practices (PDF file, 138 KB; HTML)
  • HCUP Hospital Identifiers (PDF file, 162 KB; HTML)
  NASS Refinements HCUP Tools: Labels and Formats
  • Format Programs
    • HCUP Formats Program (TXT file, 106 KB) Creates SAS formats to label the values of selected categorical data elements in HCUP files
    • HCUP Diagnosis and Procedure Groups Formats Program (TXT file, 61 KB) Creates SAS formats to label the values of HCUP Diagnosis and Procedure Groups data elements, including Clinical Classifications Software Refined (CCSR) data elements
    • ICD-10-CM Formats Program (TXT file, 12.2 MB) Creates SAS formats to label the values of ICD-10-CM Diagnoses and Procedures
Obtaining HCUP Data

Internet Citation: NASS Database Documentation. Healthcare Cost and Utilization Project (HCUP). April 2024. Agency for Healthcare Research and Quality, Rockville, MD.
Are you having problems viewing or printing pages on this website?
If you have comments, suggestions, and/or questions, please contact
Privacy Notice, Viewers & Players
Last modified 04/10/24