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-owned ED visits. Unweighted, it contains data from approximately 34 million ED visits each year. Weighted, it estimates roughly over 144 million ED visits. Developed through a Federal-State-Industry partnership sponsored by the Agency for Healthcare Research and Quality, HCUP data inform decision making at the national, State, and community levels.

This page provides an overview of the AHRQ HCUP NEDS. For more details, see NEDS Database Documentation and the Introduction to the NEDS, 2024 (PDF file, 1018 KB) and prior years.

• What's New in the 2024 AHRQ HCUP NEDS?
• About the AHRQ HCUP NEDS
• AHRQ HCUP NEDS File Structure
• AHRQ HCUP NEDS Data Elements
• Areas of Research and HCUP Publications
• Purchase the AHRQ HCUP NEDS
• NEDS Hardware and Software Requirements

• Because of a change in the states available to participate in the 2024 NEDS and a need to produce accurate national estimates, the following modifications have been made to the data elements included in the NEDS:
  • Information available on hospital charges:
    • For treat-and-release ED visits, the data element TOTCHG_ED_2024 includes two separate adjustments to the hospital charge for treat-and-release ED visits in the Western and Midwest regions. The adjustment is specific to the West and Midwest because the sampling of hospital-owned emergency departments in those regions are most impacted by the change in available data.
    • For ED visits that result in an admission to the same hospital, the data element specific to hospital charge for the inpatient stay (TOTCHG_IP) is not included in the 2024 NEDS and the data element specific to the hospital charge for ED services (TOTCHG_ED_2024) is set to missing. This is consistent with the handling of TOTCHG_ED_2023 in the 2023 NEDS.
• Changes to the Diagnosis and Procedure Groups file:
  • Used v2026.2 for the Clinical Classifications Software Refined (CCSR) for ICD-10-PCS procedures and used v2026.1 for all other HCUP software tools included in the Diagnosis and Procedures Group file.
• For more information on NEDS data elements, see the NEDS Description of Data Elements.
• Please note that these modifications to the 2024 NEDS data elements may make comparisons of some estimates across years more difficult. See the Introduction to the NEDS, for 2024 (PDF) for more details.

Researchers and policymakers use AHRQ's NEDS to make national estimates of ED care. The NEDS tracks information about the emergency department (ED) visits across the country. It is drawn from the State Inpatient Databases (SID) and State Emergency Department Databases (SEDD). The SID contain information on patients initially seen in the ED and subsequently 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 2024, which allow researchers to analyze trends over time.

For more details on the 2024 NEDS, see the Introduction to the NEDS, 2024 (PDF file, 1018 KB).

Information on previous years of the NEDS may be found in prior years of the Introduction to the NEDS at https://hcup-us.ahrq.gov/db/nation/neds/nedsarchive.jsp.

The NEDS is an annual, calendar year file, except for data year 2015, which was split into two parts because of the switch from ICD-9-CM to ICD-10-CM/PCS coding. There are four discharge-level files and one hospital-level file:

NEDS Discharge-Level files

• Core File contains records for all the ED visits in the SID and SEDD whether resulting in admission or not from the sample of hospitals in participating States and the District of Columbia.
  • This file is available in all years of the NEDS.
• Supplemental ED File contains additional information for patients who were treated in the ED and not admitted directly to the hospital (e.g., released home, transferred). This information came from the SEDD.
  • This file is available in all years of the NEDS.
  • The unique NEDS record identifier (KEY_ED) provides the linkage between the NEDS Core File and the Supplemental ED File. For patients seen in the ED and admitted to the same hospital (SID records), information about the stay is contained in the Supplemental Inpatient File.
• Supplemental Inpatient File contains data elements that are specific to the inpatient stay, such as total charges, length of inpatient stay, and procedure codes from the SID record. Procedures reported on the SID records may have been performed in the ED, but currently there is no way to verify this information.
  • This file is available in all years of the NEDS.
  • The unique NEDS record identifier (KEY_ED) provides the linkage between the NEDS Core File and the Supplemental Inpatient File.
• Diagnosis and Procedure Groups Files contains additional information on the ICD-10-CM/PCS diagnoses and procedures created by the HCUP software tools.
  • This file is available in the NEDS beginning with data year 2018.
  • Beginning with data year 2023, data elements derived from the Chronic Conditions Indicator Refined (CCIR) for ICD-10-CM are available on the file.
  • The unique NEDS record identifier (KEY_ED) provides the linkage between the NEDS Core File and the Diagnosis and Procedure Groups File.

NEDS Hospital-level file

• Hospital Weights File contains one observation for each hospital-owned ED sampled for the NEDS, with its weight and variance estimation data elements. The unit of observation is the ED.
  • This file is available in all years of the NEDS.
  • The HCUP ED hospital identifier (HOSP_ED) provides the linkage between the NEDS Core File and the Hospital Weights File.

Users interested in applying AHRQ software tools to the NEDS for data years, including ICD-10-CM/PCS-coded data, to produce data elements currently unavailable in the database files may do so by downloading the respective tool(s) from the Research Tools section of the HCUP User Support (HCUP-US) website. Additionally, users may wish to review the HCUP Software Tools Tutorial, which provides instructions on how to apply the AHRQ software tools to HCUP or other administrative databases.

For information on changes to the NEDS in data year 2015 due to transition from ICD-9-CM to ICD-10-CM/PCS coding, refer to the document 2015 Healthcare Cost and Utilization Project (HCUP) National Emergency Department Sample: Change in Structure and Data Elements Caused by Transition to ICD-10-CM/PCS.

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:

• ICD-10-CM/PCS diagnosis, procedure, and external cause of morbidity codes (starting on October 1, 2015)
• ICD-9-CM diagnosis, procedures, and external cause of injury codes (prior to October 1, 2015)
• Current Procedural Terminology, Fourth Edition (CPT®-4) procedure codes on ED visits that do not result in an admission to the same hospital
• Identification of injury-related ED visits and the mechanism and intent of injury (the availability of these data elements varies over time)
• 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 (e.g., Medicare, Medicaid, private insurance, self-pay, no charge, and other insurance type)
• Total ED charges (for treat-and-release ED visits) and total hospital charges (for ED visits that result in admission, prior to data year 2023)
• Hospital characteristics (e.g., region, trauma center indicator, urban-rural location, teaching status)
• Data elements derived from the HCUP software tools beginning with data year 2018

Not all data elements are available for every year. For comprehensive information about the data elements and their availability by data year, see the NEDS Description of Data Elements.

For information on modifications to the NEDS data elements in data year 2024 due to changes in the participating states relative to prior years of the NEDS, see the Introduction to the NEDS, for 2024 (PDF) and the NEDS Description of Data Elements.

As a uniform, multi-state database, the NEDS promotes comparative studies of healthcare services and supports healthcare 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 and online tools:

• HCUP Statistical Briefs highlight a variety of health topics.
• Use the HCUP Publications Search Tool to find publications using the NEDS.
• Review featured publications on the HCUP Research Spotlights page.
• Read publications by the winners of the HCUP Outstanding Article of the Year Awards.
• HCUPnet allows users to query inpatient and outpatient statistics based on the HCUP databases.

NEDS releases for data years 2006 through 2024 are available for purchase online through the AHRQ HCUP Central Distributor Online Reporting System (CDORS).

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, 260 KB; HTML).

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

E-mail: HCUP-RequestData@ahrq.gov

The NEDS data set is extremely large. The data are distributed as comma-separated value (CSV) files delivered via secure digital download from the AHRQ HCUP Central Distributor Online Reporting System (CDORS). The files are compressed and encrypted with 7-Zip©.

To load and analyze the NEDS data on a computer, users will need the following:

• The password provided by the HCUP Central Distributor
• A hard drive with at least 300 GB of space available
• A third-party zip utility such as 7-Zip©, ZIP Reader, Secure ZIP®, WinZip®, or Stuffit Expander®
• 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 CSV file into SAS, SPSS, or Stata, are also available on the NEDS Database Documentation page.