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NEDS Overview
The Nationwide Emergency Department Sample (NEDS) is a set of hospital-based emergency department databases included in the HCUP family. These databases are created by AHRQ through a Federal-State-Industry partnership.
Overview of the Nationwide Emergency Department Sample (NEDS)

The Nationwide Emergency Department Sample (NEDS) is part of a family of databases and software tools developed for the Healthcare Cost and Utilization Project (HCUP). The NEDS is the largest all-payer emergency department (ED) database in the United States, yielding national estimates of hospital-based ED visits. Unweighted, it contains data from approximately 30 million discharges each year. Weighted, it estimates roughly 135 million ED visits.

Developed through a Federal-State-Industry partnership sponsored by the Agency for Healthcare Research and Quality, HCUP data inform decisionmaking at the national, State, and community levels.

This page provides an overview of the NEDS. For more details, see NEDS Database Documentation and the Introduction to the NEDS, 2013 (PDF file, 956 KB; HTML).


Sampled from the State Inpatient Databases (SID) and State Emergency Department Databases (SEDD), HCUP's NEDS can be used to create national and regional estimates of ED care. The SID contain information on patients initially seen in the ED and then admitted to the same hospital. The SEDD capture information on ED visits that do not result in an admission (i.e., treat-and-release visits and transfers to another hospital).

NEDS data are available from 2006 through 2013, which allows researchers to analyze trends over time. Key features of the most recent NEDS database year (2013) include:
  • A large sample size, which provides sufficient data for analysis across hospital types and the study of relatively uncommon disorders and procedures
  • Discharge data for ED visits from 947 hospitals located in 30 States, approximating a 20-percent stratified sample of U.S. hospital-based EDs
  • Demographic data such as hospital and patient characteristics, geographic area, and the nature of ED visits (e.g., common reasons for ED visits, including injuries)
  • ED charge information for over 85 percent of patients, including individuals covered by Medicare, Medicaid, or private insurance, as well as those who are uninsured
  • Children's hospitals with trauma centers, which are classified with adult and pediatric trauma centers in the current versions of the NEDS.
Information on previous years of the NEDS may be found in the Introduction to the NEDS, 2013 (PDF file, 956 KB).
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The NEDS contains clinical and resource-use information that is included in a typical discharge abstract, with safeguards to protect the privacy of individual patients, physicians, and hospitals (as required by data sources). The NEDS is composed of more than 100 clinical and nonclinical variables for each hospital stay. These include:
  • International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis and external cause of injury codes
  • ICD-9-CM and Current Procedural Terminology, Fourth Edition (CPT®-4) procedure codes
  • Identification of injury-related ED visits including mechanism, intent, and severity of injury
  • Admission and discharge status
  • Patient demographics characteristics (e.g., sex, age, urban-rural designation of residence, national quartile of median household income for patient's ZIP Code)
  • Expected payment source
  • Total ED charges (for ED visits) and total hospital charges (for inpatient stays for ED visits that result in admission)
  • Hospital characteristics (e.g., region, trauma center indicator, urban-rural location, teaching status)
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As a uniform, multi-State database, the NEDS promotes comparative studies of health care services and supports health care policy and research on a variety of topics, including:
  • Use of and charges for ED services
  • Medical treatment effectiveness
  • Quality of ED care
  • Impact of health policy changes
  • Access to care
  • Utilization of health services by special populations
The NEDS is used in a variety of publications: Return to Contents

NEDS releases for data years 2006 through 2013 are available for purchase through the HCUP Central Distributor.

All HCUP data users, including data purchasers and collaborators, must complete the online HCUP Data Use Agreement Training Tool, and must read and sign the Data Use Agreement for Nationwide Databases (PDF file, 55 KB; HTML).

The NEDS are available for purchase online through the HCUP Central Distributor.

Questions regarding purchasing databases can be directed to the HCUP Central Distributor:

Telephone: (866) 556-4287 (toll free)
Fax: (866) 792-5313 (toll free)

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The NEDS data set is extremely large. The data are sent in comma-separated value (CSV) format compressed with WinZip®. In order to load and analyze the NEDS data on a computer, you will need the following:
  • A DVD drive
  • A hard drive with 60 to 100 gigabytes of space available
  • A third-party zip utility such as ZIP Reader, 7-Zip, or WinZip®
  • SAS®, SPSS®, Stata® or similar analysis software
The data set includes weights for producing national and regional estimates. NEDS documentation and tools, including programs for loading the ASCII file into SAS, SPSS, or Stata, are also available on the NEDS Database Documentation page.

Please note the following based on the software you plan to use:
  • In total, the comma-delimited version of the NEDS is almost 14 gigabytes (GB).
  • The NEDS files loaded into SAS are about 11 GB. Most SAS data steps will require twice the storage of the file, so that the input and output files can coexist. The largest use of space typically occurs during a sort, which requires work space approximately three times the size of the file. Thus, the NEDS files would require approximately 33 GB of available workspace to perform a sort.
  • The NEDS files loaded into SPSS are under 30 GB.
  • Because Stata loads the entire file into memory, it may not be possible to load every data element in the NEDS Core file into Stata. Stata users will need to maximize memory and use the "_skip" option to select a subset of variables. More details are provided in the Stata load programs.
With a file this size and without careful planning, space could easily become a problem in a multi-step program with the NEDS. It is not unusual to have several versions of a file marking different steps while preparing it for analysis and more versions for the actual analyses; therefore, users should be aware that the amount of space required can escalate rapidly.

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Internet Citation: NEDS Overview. Healthcare Cost and Utilization Project (HCUP). January 2016. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 1/4/16