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

NASS Overview

HCUP Partners in the NASS

Introduction to the NASS
- 2022 (PDF file, 2 MB)
- Prior Years
NASS Related Reports
Checklist for Working With the NASS

Restrictions on Use

HCUP Data Use Agreement Training
Data Use Agreement for the Nationwide Databases (PDF file, 260 KB; HTML)
Requirements for Publishing with HCUP Data

File Specifications and Load Programs

Data Elements

NASS Description of Data Elements
NASS Summary Statistics
Frequencies by Diagnosis and Procedure Codes, NASS 2016-2021 (Excel file, 12 MB)

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

Known Data Issues

2021

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

Purchase HCUP data from the HCUP Central Distributor

User Support