HCUP e-News: the electronic newsletter of the Healthcare Cost and Utilization Project

Winter 2020
Issue #65


News and Announcements: Notable news from HCUP
Databases and Products: New database and product releases
Publication Spotlights: Recent works incorporating HCUP data and tools
HCUP Q&A: Answers to your HCUP questions
HCUP Events: Upcoming HCUP conferences and meetings

Missed the last HCUP e-News? Read it on the HCUP-US website.

News and Announcements

Now Available: 2018 HCUP National Inpatient Sample (NIS) and Nationwide Emergency Department Sample (NEDS)

In November, the Agency for Healthcare Research and Quality (AHRQ) released the 2018 National Inpatient Sample (NIS) and Nationwide Emergency Department Sample (NEDS).

A powerful database that contains data from more than 7 million hospital inpatient records, the NIS is drawn from the HCUP State Inpatient Databases (SID), which include all inpatient data that are currently contributed to HCUP. Forty-seven States and the District of Columbia participate in the NIS, covering more than 97 percent of the U.S. population. NIS data can be weighted to produce national estimates, allowing researchers and policymakers to identify, track, and analyze national trends in healthcare utilization, access, charges, quality, and outcomes. The NIS is the largest publicly available inpatient healthcare database in the United States. It includes all patients, regardless of expected payer for the hospital stay.

The NEDS is the largest publicly available all-payer emergency department (ED) database in the United States. It enables analyses of ED utilization patterns and supports public health professionals, administrators, policymakers, and clinicians in their decision making regarding this critical source of care. Constructed using records from both the HCUP State Emergency Department Databases (SEDD) and the SID, the 2018 NEDS contains data from more than 35 million ED visits in 36 States and the District of Columbia—approximating a 20 percent stratified sample of visits to U.S. hospital-owned EDs. Weights are provided to calculate national estimates pertaining to the roughly 143 million ED visits that took place in 2018. The NEDS provides information on patients admitted to the hospital through the ED and on patients treated and released or transferred to another hospital from the ED.

HCUP nationwide and State-level databases (including the NIS and NEDS) are available for purchase through the HCUP Central Distributor. Earlier years of the NIS and NEDS also are available.

Coming Soon: The 2018 Nationwide Readmissions Database (NRD) and Nationwide Ambulatory Surgery Sample (NASS)

AHRQ is scheduled to release the 2018 Nationwide Readmissions Database (NRD) and Nationwide Ambulatory Surgery Sample (NASS) in December.

The NRD is a database of all-payer hospital inpatient stays that can be used to generate national estimates of readmissions. It addresses a large gap in healthcare data—the lack of nationally representative information on hospital readmissions for all ages. Unweighted, the NRD contains data from approximately 18 million discharges each year. Weighted, it estimates roughly 35 million discharges. The NRD uses SID with verified patient linkage numbers and includes discharges from community hospitals, excluding rehabilitation and long-term acute care hospitals. It includes discharges for patients with and without repeat hospital visits and for those who died in the hospital. The NRD is designed to be flexible to various types of readmission analyses. Repeat hospital visits may or may not be related.

The NASS is the largest all-payer ambulatory surgery database in the United States. The NASS can be used to create national estimates of major ambulatory surgery encounters performed in hospital-owned facilities. Unweighted, it contains approximately 8 million ambulatory surgery encounters each year and approximately 10 million ambulatory surgery procedures. Weighted, it estimates approximately 11 million ambulatory surgery encounters and 14 million ambulatory surgery procedures. The NASS was created to enable analyses of selected ambulatory surgery utilization patterns and to support public health professionals, administrators, policymakers, and clinicians in their decision making regarding this critical source of care. 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.

Users are encouraged to sign up for the HCUP Mailing List to be notified of upcoming database releases.

Learn More About the NEDS During Upcoming HCUP User Webinars

On December 8 and December 10, AHRQ will host a webinar series featuring an in-depth presentation on the NEDS. The NEDS can be used to create national and regional estimates of ED visits, regardless of whether they resulted in admission. One of the most distinctive features is its large sample size, which allows for analysis across hospital types and the study of relatively uncommon disorders.

Presenters will provide an overview of the NEDS, including information about the database design, the importance of weighting the data to produce national estimates of ED visits, and included data elements. Three use cases will showcase how to work with the database: variation in ED utilization for injuries by type of trauma center, an investigation of differences in population-based rates for potentially preventable hospitalizations such as heart failure and asthma, and fluctuations over time in ED visits for seasonal illness. Presenters will conclude with an overview of how to compare results from the NEDS with output from HCUPnet (a free online query tool), followed by a final checklist of items researchers should keep in mind while working with the NEDS.

The webinar will be open to the public at no charge and will require advance registration. Registration opens on December 1, 2020. To register, please visit the HCUP Workshops and Webinars page.

Updates to HCUP Software Tools for ICD-10-CM/PCS Codes, HCPCS Level I (CPT®) Codes, and HCPCS Level II Codes

The HCUP Software Tools are updated annually to coincide with fiscal year (FY) updates to the International Classification of Diseases, Tenth Revision, Clinical Modification/Procedure Coding System (ICD-10-CM/PCS) and calendar year (CY) updates for Current Procedural Terminology (CPT) and Healthcare Common Procedure Coding System (HCPCS) Level II codes. AHRQ has released the following updated HCUP Software Tools:

Tools Using ICD-10-CM/PCS Codes

Tools Using CPT or HCPCS Level II Codes

See the Tools & Software section of HCUP-US for more information on the changes to each tool.

New Data on HCUPnet

Readmission statistics from the 2016–2017 NRD and selected data from the 2017 SID have been added to HCUPnet, the free, online query system that provides statistics and data tables based on HCUP data. Information on 7-day and 30-day hospital readmissions from the NRD is available to support various types of analyses of national readmission rates for all patients, regardless of the expected payer for the hospital stay. Statistics from the SID are well suited for inpatient research that requires complete enumeration of hospitals and discharges within geographic areas or States. In addition, the uniform format of the SID helps facilitate cross-State comparisons.

HCUPnet’s easy, step-by-step process allows users to explore many healthcare topics relating to hospital inpatient services and ED settings. Users can also generate tables and graphs on national, regional, and county-level statistics, including hospital readmissions and trends on hospital and ED use in the United States.

To explore the updates and start your own query, visit HCUPnet today at https://hcupnet.ahrq.gov/.

Databases and Products

Recently Released: 2019 State Databases and Additional 2016–2018 Databases

Since September 2020, the following State databases have been released:

In addition, the 2018 NIS and NEDS have been released. The 2018 NRD and NASS are scheduled for release later in December.

Complete listings of available databases by year can be found in the Database Catalog on the HCUP-US website. Databases can be purchased online through the HCUP Central Distributor, and aggregated national and selected State statistics can be accessed via HCUPnet.

***Please note, some HCUP Central Distributor operations have been affected by the current national emergency related to COVID-19. Please refer to the notice posted on the HCUP Central Distributor for current status information.

Publication Spotlights

New HCUP Statistical Briefs Posted on HCUP-US

Since September 2020, the following HCUP Statistical Briefs have been released:

To access these and other Statistical Briefs, please visit the Statistical Briefs page on the HCUP-US website.

New HCUP Methods Series Report Now Available

Since September 2020, the following HCUP Methods Series have been released:

These and other HCUP reports can be found on the HCUP Reports page of the HCUP-US website.


Question:: I am interested in working with the Elixhauser Comorbidity Software Refined for ICD-10-CM and noticed that a new version was released. I have some questions about the newly updated tool before I begin using it for my analysis.


What updates were made to the Elixhauser Comorbidity Software Refined for ICD-10-CM v2021.1?

The Elixhauser Comorbidity Software Refined for ICD-10-CM retains the same clinical intent of defining a comprehensive list of comorbidity measures for use with large administrative databases; however, refinements were made to the clinical criteria used for identification of comorbidities and also with some of the comorbidity measures themselves. The number of comorbidity measures increases from 29 to 38 in v2021.1, with 3 measures added, 5 measures modified to create 12 more specific measures, and 1 measure discontinued. Following clinical review, diagnosis codes have been added and removed and some diagnoses are mapped to more than one comorbidity measure.

Additionally, Medicare Severity-diagnosis related groups (MS-DRGs) are no longer being used to exclude secondary diagnoses related to the principal diagnoses. Instead, a subset of the comorbidity measures use the present on admission (POA) indicator to determine whether the condition indicated by the secondary diagnosis arose prior to or during the hospital stay (i.e., whether the condition was pre-existing). The remaining comorbidity measures do not use POA indicators because the condition can be assumed to be pre-existing and not the result of hospital care (e.g., diabetes, AIDS). An index (one number) to describe the comorbidities is under development for future release.

For additional details on the refinement process, refer to the User Guide for the Elixhauser Comorbidity Software Refined for ICD-10-CM.

Prior versions of the Elixhauser Comorbidity Software tool can only be used with hospital inpatient administrative data. Is this still true with the Elixhauser Comorbidity Software Refined for ICD-10-CM v2021.1?

Beginning with v2021.1 of the Elixhauser Comorbidity Software Refined for ICD-10-CM, the tool can be applied to both hospital inpatient and outpatient administrative data. Prior versions of the tool were only applicable to inpatient data because of the use of MS-DRGs to identify comorbidities. The use of MS-DRGs has been replaced with indicators of the diagnosis being POA.

Are there resources available to researchers using the Elixhauser Comorbidity Software Refined for ICD-10-CM?

There are three key pieces of documentation available to assist researchers using v2021.1 of the Elixhauser Comorbidity Software Refined for ICD-10-CM tool:

For additional information on the User Guide and other resources, refer to the Elixhauser Comorbidity Software Refined for ICD-10-CM page on the HCUP-US website.

HCUP Events

For a complete list of HCUP presentations and events, visit the HCUP Events Calendar.

HCUP e-News is available online on the HCUP-US website and distributed via the HCUP Mailing List.

For more information and questions regarding the HCUP e-News, please email hcup@ahrq.gov