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HCUP Frequently Asked Questions
The HCUP FAQs provide quick, concise answers to commonly asked HCUP questions.
 
HCUP Frequently Asked Questions

This page provides answers to commonly asked questions about obtaining and using the Healthcare Cost and Utilization Project (HCUP) databases, software tools, supplemental files, and other products, and about data use restrictions and publishing with the data. If you still have questions, please review the following information.

For questions about using the HCUP databases, software tools, supplemental files, and other products, or about data use restrictions and publishing with the data, contact HCUP User Support at HCUP@ahrq.gov. Additional information regarding HCUP User Support is located in the About HCUP User Support section below.

For questions concerning HCUP database purchases, current HCUP database orders and invoices, downloading nationwide HCUP databases, unzipping State or nationwide HCUP database products, the submission of required HCUP Data Use Agreements (DUAs), training certificate codes, or data re-use requests, please review the Purchasing FAQs, or contact the HCUP Central Distributor at HCUPDistributor@ahrq.gov.

For questions about using the Agency for Healthcare Research and Quality (AHRQ) Quality Indicators™, contact QIsupport@ahrq.hhs.gov.


Contents
 

  • What is HCUP?

    The Healthcare Cost and Utilization Project (called "H-CUP") is a family of health care databases, software tools, and products developed through a Federal-State-Industry partnership and sponsored by the Agency for Healthcare Research and Quality (AHRQ). HCUP databases bring together the data collection efforts of State data organizations, hospital associations, private data organizations, and the Federal government to create a national information resource of patient discharge-level health care data.

    HCUP includes the largest collection of longitudinal hospital care data in the United States, with all-payer, encounter-level information beginning in 1988. HCUP is derived from administrative data originally collected for billing purposes. These databases enable research on a broad range of health policy issues, including cost and quality of health services, medical practice patterns, access to health care programs, and outcomes of treatments at the national, State, and local levels.

    HCUP offers free software tools that facilitate use of the data, including HCUPnet, an online query system that provides immediate access to statistics on hospital inpatient, emergency department, and ambulatory surgery use, cost, and readmissions.

    HCUP Fast Stats provides easy access to the latest HCUP-based statistics for health care information topics using visual statistical displays in stand-alone graphs, trend figures, or simple tables to convey complex information at a glance.

    HCUP offers online reports, including HCUP Statistical Briefs which present simple, descriptive statistics on a variety of specific topics.

    For additional information, please visit the Overview of HCUP page and take the Online HCUP Overview Course.


  • What types of health care settings are captured in HCUP data?

    The HCUP databases are built from hospital administrative data (i.e., hospital billing records). The databases cover hospital inpatient care, outpatient emergency department care, and ambulatory surgery from hospital-owned facilities. Some State Ambulatory Surgery Databases (SASD) include ambulatory surgery data from facilities not owned by a hospital. HCUP does not include services provided in physician offices, and does not contain complete or reliable pharmacy, laboratory, pathology, or radiology information.


  • Under the Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule, how are the HCUP databases defined?

    The HCUP databases are consistent with the definition of limited data sets under the HIPAA Privacy Rule and contain no direct patient identifiers. HCUP Data Use Agreement (DUA) training and a signed DUA are required to purchase and/or use the HCUP databases.


  • What is HCUP's unit of analysis?

    The unit of analysis in the HCUP databases is the discharge record, not individual patients. The exception to this is in the readmission files, in which the unit of analysis is the patient.


  • How can I keep informed about HCUP activities and product releases?

    Sign up for the HCUP Mailing List to receive emailed information about database releases, tools, and other HCUP product news. You also can check the HCUP-US News and Events page for updates.
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  • What is the HCUP Online Tutorial Series?

    The HCUP Online Tutorial Series is a set of free, interactive courses designed to provide data users with information about HCUP data and tools, as well as training on technical methods for conducting research with HCUP data.


  • What topics are available?

    Topics in the Online Tutorial Series include the following:

    • HCUP Overview Course: provides information about HCUP data, software tools, and products.
    • Load and Check HCUP Data Tutorial: provides instructions on how to unzip (decompress) HCUP data, save it on the computer, and load the data into a standard statistical software package.
    • Calculating Standard Errors Tutorial: shows users how to accurately determine the precision of the estimates produced from the HCUP nationwide databases.
    • Nationwide Readmissions Database (NRD) Tutorial: introduces users to the design, data, and uses for this nationwide database.
    • HCUP Sample Design Tutorial: explains the sampling strategy of the National (Nationwide) Inpatient Sample (NIS), Kids' Inpatient Database (KID), and Nationwide Emergency Department Sample (NEDS) nationwide databases.
    • Producing National HCUP Estimates Tutorial: demonstrates how the NIS, KID, and NEDS nationwide databases can be used to produce national and regional estimates.
    • Multi-Year Analysis Tutorial: presents solutions that may be necessary when conducting analyses that span multiple years.
    • HCUP Tools Loading Tutorial: provides instructions on how to unzip (decompress) the HCUP software tools for International Classification of Diseases, Tenth Revision, Clinical Modification/Prodcedure Coding System (ICD-10-CM/PCS), save it on the computer, and load the tool into a standard statistical software package for application to HCUP or other administrative databases.
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  • How can I learn more about the transition to ICD-10-CM/PCS coding from the Ninth Revision, Clinical Modification (ICD-9-CM) and its impact on the file structure and data elements in the 2015 HCUP databases?

    For information on the transition to ICD-10-CM/PCS, revised file structure in the 2015 HCUP databases, and resources for working with the 2015 HCUP databases, please see the ICD-10-CM/PCS Resources page.
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  • What are HCUP's nationwide databases?

    HCUP's nationwide databases provide estimates for hospital stays or emergency department encounters across the United States. Consisting of the NIS, the KID, the NRD, and the NEDS, the nationwide databases are built from stratified, random samples of HCUP's State Databases. They include stays covered by all payers (Medicare, Medicaid, private insurance, and the uninsured). The databases can be used to create national estimates of health care utilization, access, charges, quality, and outcomes. The HCUP nationwide databases are available for purchase through the HCUP Central Distributor. Statistics from the databases are available on HCUPnet.


  • Do I need to weight my nationwide database data?

    Yes, HCUP's nationwide databases need to be weighted to produce national estimates. HCUP's free online tutorial called Producing National HCUP Estimates provides instruction on the process.


  • When are the nationwide databases generally released, and what years of data are available?

    The NIS, the NRD, and the NEDS are released annually, approximately 18 to 22 months following the end of a calendar year. Data years begin with 1988 for the NIS, 2010 for the NRD, and 2006 for the NEDS.

    The KID is released every 3 years, approximately 18 months following the end of a calendar year. Data years begin with 1997 and run through 2012. The KID resumed release in 2016.

    Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog. Database releases also are noted on a monthly basis in the HCUP Database and Product Releases Calendar.
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  • What is the National Inpatient Sample?

    The National Inpatient Sample (NIS) is the largest publicly available all-payer inpatient care database in the United States, yielding national estimates of hospital inpatient stays. In 2012, the National Inpatient Sample replaced the original NIS (the Nationwide Inpatient Sample), which consisted of discharge data from a sample of hospitals. Sampled from the State Inpatient Databases (SID), the National Inpatient Sample (NIS) contains a systematic sample of discharges from all hospitals reporting to HCUP. It contains charge information on all patients, regardless of payer, including individuals covered by Medicare, Medicaid, private insurance, and the uninsured.

    The most recent version of the NIS (data year 2016) contains a sample of discharges from all HCUP-reporting hospitals, which totaled more than 4,500 in 2016. The 2016 NIS includes a full calendar year of data with diagnosis and procedure codes reported using the ICD-10-CM/PCS coding system. The 2016 NIS file structure is different from the 2015 file structure, which includes both ICD-9-CM and ICD-10-CM/PCS coding. The 2016 file structure is similar to that from 2014 and earlier years, although data elements derived from AHRQ software tools are not included because the ICD-10-CM/PCS versions are still under development.

    For 2015 data, because of the transition to ICD-10-CM/PCS on October 1, 2015, data elements related to diagnoses and procedures are included in files that are split into two parts. The first 9 months of the 2015 NIS contain ICD-9-CM codes, and the last 3 months contain ICD-10-CM/PCS codes. Data elements and the data structure for the 2015 NIS have been changed. Trends based on diagnoses or procedures will be affected.

    Additional information on the NIS, including a description of data elements and summary statistics, can be found on the NIS Database Documentation page. The database can be purchased through the HCUP Central Distributor, and statistics from the NIS are available on HCUPnet.


  • What is the Nationwide Inpatient Sample?

    The Nationwide Inpatient Sample (NIS) contains discharge data from a national sample of community hospitals for data years prior to 2012. Sampled from the SID, the NIS includes all discharge data from more than 1,000 hospitals each year, approximating a 20 percent stratified sample of U.S. community hospitals through the 2011 data year. The NIS contains charge information on all patients, regardless of payer, including individuals covered by Medicare, Medicaid, private insurance, and the uninsured.

    Starting with database year 2012, the Nationwide Inpatient Sample was replaced with the National Inpatient Sample. The National Inpatient Sample uses a redesigned sampling method and contains data on more than seven million hospital stays each year that can be weighted to make national estimates.


  • What are the differences between the Nationwide Inpatient Sample and the National Inpatient Sample?

    The National Inpatient Sample replaces the Nationwide Inpatient Sample for database year 2012 onward. The National Inpatient Sample implements an improved sample design for more accurate representation of national discharge data. The previous NIS contained all discharge records from a sample of hospitals participating in HCUP. The revised database contains a sample of discharge records from all hospitals participating in HCUP.

    The database was redesigned in 2012 to improve national estimates. The redesign reflects three types of changes:

    • Revisions to the sample design, which now creates a sample of discharge records from all HCUP-participating hospitals rather than all discharge records from a sample of hospitals
    • Revisions to the definition of the discharge universe
    • Revisions to enhance confidentiality by eliminating State identifiers and data elements that are not uniformly available across States.

    The new sample strategy is expected to result in more precise estimates than the previous NIS design by reducing sampling error: for many estimates, confidence intervals under the new design are about half the length of confidence intervals under the previous design. For a detailed description of the NIS redesign, please refer to the NIS Redesign Report (PDF file, 2.1 MB).


  • Can I perform State-level analyses with the NIS?

    The sampling methodology used to create the NIS does not include State as a stratifier; therefore analysts cannot use the database to generate State-level estimates. Although the NIS includes weights to allow researchers to generate national estimates from the raw counts, no weights are included for the calculation of State-level estimates.

    For information on State-specific inpatient stays, we recommend that you work with the HCUP SID.

  • Can I perform multi-year or trend analysis using the NIS?

    Because the NIS spans more than 20 years of data, it is a good tool for longitudinal analysis. However, the NIS has undergone various changes over time, including changes to the sampling and weighting strategies used. The NIS was significantly redesigned for database year 2012. For trend analysis spanning 2012 and earlier years, NIS data weights should be used to make estimates comparable to the new 2012 NIS design.

    To perform multi-year or trends analysis using the NIS, AHRQ developed new discharge trend weights for the 1993-2011 NIS. These weights were calculated in the same way that weights were calculated for the redesigned 2012 NIS and are designed to be used instead of the original NIS discharge weights for trend analyses.

    For trend analyses using NIS data from 2011 and earlier, revised weights should be used to make estimates comparable to the new design beginning with 2012 data. Use the trend weight (TRENDWT) in place of the original discharge weight (DISCWT) to create national estimates for trend analysis. For 2012 data, no trend weight is necessary and the discharge weight supplied on the NIS files can be used. The trend weights are available for download as ASCII files along with SAS®, Stata®, and SPSS® load programs from the HCUP-US Web site.

    These new 1993-2011 trend weights replace the earlier NIS trend weights that were developed for the 1988-1997 NIS following the 1998 NIS redesign. The report Using the HCUP National Inpatient Sample to Estimate Trends (PDF file, 1.3 MB) is available as a Methods Series report and includes recommendations for trend analysis.


  • Are the NIS data weighted?

    NIS data sets purchased through the HCUP Central Distributor include discharge weights, which the user must apply to produce national estimates. When combining 2012 or 2013 NIS data and data from earlier years for national estimates, NIS trend weights should be applied. It is not necessary to use the trend weights (or discharge weights) with the NIS if you are not interested in producing national estimates.

    To learn how to properly weight data, consult HCUP's free online tutorial called Producing National HCUP Estimates, which describes the process of applying the weighting to your data.

    Please note that if you are using HCUPnet (HCUP's free, online query system), the weighting already has been applied—the statistics produced are national estimates.


  • How often is the NIS released, and what years are available?

    The NIS is released annually, approximately 18 months after the end of a calendar year. Data years begin with 1988. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog.


  • Why is the file structure different in the 2015 NIS?

    Because of the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015, the file structure of the 2015 HCUP nationwide databases differs from that of the annual files for past and future years. For information on the transition to ICD-10-CM/PCS, revised file structure in the 2015 NIS, and resources for working with the 2015 HCUP databases, please see the NIS Database Documentation page or the ICD-10-CM/PCS Resources page.


  • What are some best practices when working with the NIS?

    To ensure researchers' appropriate use of the NIS, AHRQ released a Checklist for Working With the NIS. The checklist, available for download here on the HCUP-US Web site, helps researchers, manuscript peer reviewers, and journal editors understand the NIS database design, its strengths and limitations, and how it has changed over time. The checklist provides a step-by-step guide detailing key elements to consider when evaluating NIS studies.

    Additionally, the checklist refers to informational resources covering four key topics:

    • NIS data use and acknowledgements
    • Research design
    • Data analysis
    • Transition from ICD-9-CM to ICD-10-CM/PCS.


    The checklist was derived from the JAMA article titled Adherence to Methodological Standards in Research Using the National Inpatient Sample by Khera and colleagues.

  • How much does the NIS cost?

    Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog. Cost varies by year of data. Student pricing is available.

    Additionally, statistics and data tables from the NIS are available on HCUPnet, HCUP's free, online query system.
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  • What is the Kids' Inpatient Database (KID)?

    The KID is the largest publicly available all-payer pediatric inpatient care database in the United States, yielding national estimates of hospital inpatient stays for patients younger than 21 years of age. Unweighted, it contains data from approximately three million pediatric discharges each year that can be weighted to make national estimates for pediatric care. Weighted, it estimates approximately six million hospital stays for children. The KID is built from a sample of pediatric discharges from the SID.

    The KID has been produced every 3 years (1997, 2000, 2003, 2006, 2009, 2012). Hospital discharge data for 2015 contains a mix of ICD-9 and ICD-10 data—the first three quarters of 2015 contain ICD-9-CM data, and the last quarter contains ICD-10-CM/PCS data. Because of the complexities of analyzing a mixed data year, the KID was not released for 2015 but instead was released for 2016. The 2016 KID consists of ICD-10-CM/PCS data only. The 2016 KID includes discharges from 4,200 hospitals in 46 States plus the District of Columbia.

    Although the KID is released every 3 years, the data include discharges for the single calendar year (January to December). The KID's large sample size enables analyses of common as well as rare conditions, such as congenital anomalies, and uncommon treatments, such as organ transplantation. The KID includes charge information on all patients, regardless of payer, including children covered by Medicaid, private insurance, and the uninsured.

    Additional information on the KID, including a description of data elements and summary statistics, can be found on the KID Database Documentation page. The database can be purchased through the HCUP Central Distributor, and statistics from the KID are available on HCUPnet.


  • How is the KID different from the NIS?

    The KID is based on a stratified, random sample of pediatric discharges (patients younger than 21 years of age) from the SID. Ten percent of normal newborns and 80 percent of other pediatric discharges (age 20 years or younger at admission) from 4,200 U.S. community hospitals (defined as short-term, non-Federal, general and specialty hospitals, excluding hospital units of other institutions), excluding rehabilitation hospitals. A large sample size enables analyses of rare conditions (e.g., congenital anomalies) as well as uncommon treatments (e.g., cardiac surgery).

    The NIS does not oversample complicated newborns and other (nonnewborn) pediatric discharges. The 2012 NIS is a sample of discharges from all hospitals participating in HCUP. Starting with 2012 data, the NIS was redesigned to improve national estimates; the previous NIS contained all discharge records from a sample of hospitals participating in HCUP.


  • Are the KID data weighted?

    KID data purchased through the HCUP Central Distributor include discharge weights, which must be applied by the user to produce national estimates. To learn how to properly weight data, consult HCUP's free online tutorial Producing National HCUP Estimates, which describes the process of weighting data.

    Please note that if you are using HCUPnet (our free, online query system), the weighting already has been applied — the statistics produced are national estimates.


  • How often is the KID released, and what years are available?

    Unlike HCUP's other databases, which are released annually, the KID was released every 3 years beginning with 1997 data through 2012. The KID resumed release in 2016 following the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015. Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog.


  • How much does the KID cost?

    Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog. Cost varies by year of data. Student pricing is available.

    Additionally, statistics and data tables from the KID are available on HCUPnet, HCUP's free, online query system.
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  • What is the Nationwide Emergency Department Sample (NEDS)?

    The NEDS is the largest publicly available all-payer emergency department (ED) database in the United States, yielding national estimates of ED visits. Unweighted, the NEDS contains approximately 33 million records each year from about 1,000 EDs. Weighted, it estimates approximately 145 million ED visits. The NEDS contains discharges from more than 950 hospitals and approximates a 20 percent stratified sample of U.S. hospital-based EDs. It is constructed using records from (1) the HCUP State Emergency Department Databases (SEDD), which capture information on ED visits that do not result in an admission (i.e., treat-and-release visits and transfers to another hospital), and (2) the SID, which contain information on patients initially seen in the ED and then admitted to the same hospital. The NEDS includes ED charge information for approximately 78 percent of all U.S. ED visits, regardless of payer, including individuals covered by Medicare, Medicaid, private insurance, and the uninsured.

    The most recent version of the NEDS (data year 2016) includes discharges from 953 hospital-based EDs in 36 States and the District of Columbia. The 2016 NEDS includes a full calendar year of data with diagnosis and procedure codes reported using the ICD-10-CM/PCS coding system. The 2016 NEDS file structure is different from the 2015 file structure, which includes both ICD-9-CM and ICD-10-CM/PCS coding. The 2016 file structure is similar to that of 2014 and earlier years, although data elements derived from AHRQ software tools are not included because the ICD-10-CM/PCS versions are still under development. For 2015 data, because of the transition to ICD-10-CM/PCS on October 1, 2015, data elements related to diagnoses and procedures are included in files that are split into two parts. The first 9 months of the 2015 NEDS contain ICD-9-CM codes, and the last 3 months contain ICD-10-CM/PCS codes. Data elements and the data structure for the 2015 NEDS have been changed. Trends based on diagnoses or procedures will be affected.

    Additional information on the NEDS, including a description of data elements and summary statistics, can be found on the NEDS Database Documentation page. The database can be purchased through the HCUP Central Distributor, and statistics from the database are available on HCUPnet.


  • Does the NEDS contain ICD-9-CM/ICD-10-CM/PCS procedure codes or Current Procedural Terminology (CPT®) codes?

    The NEDS contains both types of procedure codes; however, the type of code(s) depends on the State and the type of ED visit. For ED visits that do not result in hospitalization, procedures may be reported as both ICD-9-CM/ICD-10-CM/PCS and CPT, Fourth Edition (CPT-4) procedure codes. Information on availability by State can be found under the Availability of Data Elements by Year link located on the SEDD Database Documentation page of the HCUP-US Web site. This information may vary by year, so please refer to the data year corresponding to the NEDS of interest.

    For ED visits resulting in hospitalization, procedures are coded as ICD-9-CM/ICD-10-CM/PCS codes but also are sometimes available in CPT codes. Information on availability by State can be found under the Availability of Data Elements by Year link located on the SID Database Documentation page of the HCUP-US Web site. This information may vary by year, so please refer to the data year corresponding to the NEDS of interest.


  • Are the NEDS data weighted?

    NEDS data purchased through the HCUP Central Distributor include discharge weights, which the user must apply to produce national estimates. To learn how to properly weight data, consult HCUP's free online tutorial Producing HCUP National Estimates, which describes the process of weighting data.

    Please note that if you are using HCUPnet (our free, online query system), the weighting already has been applied—the statistics produced are national estimates.


  • How often is the NEDS released, and what years are available?

    The NEDS is released annually, approximately 18 to 22 months after the end of a calendar year. Data years begin with 2006. Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog.


  • Why is the file structure different in the 2015 NEDS?

    Due to the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015, the file structure of the 2015 HCUP nationwide databases differs from the structure of annual files for past and future years. For information on the transition to ICD-10-CM/PCS, the revised file structure in the 2015 NEDS, and resources for working with the 2015 HCUP databases, please see the NEDS Database Documentation page or the ICD-10-CM/PCS Resources page.


  • How much does the NEDS cost?

    Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog. Student pricing is available.

    Additionally, statistics and data tables from the NEDS are available on HCUPnet, HCUP's free, online query system.
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  • What is the Nationwide Readmissions Database (NRD)?

    The NRD is the largest publicly available all-payer readmissions database in the United States that can be used to examine national estimates of readmissions. Unweighted, it contains approximately 17 million discharges each year. Weighted, it estimates approximately 36 million discharges. The NRD is drawn from the SID and contains verified patient linkage numbers that can be used to track a person across hospitals within a State.

    The most recent version of the NRD (data year 2016) includes data from 27 HCUP Partners. These States are geographically dispersed and account for 57.8 percent of the total U.S. population and 56.6 percent of all U.S. hospitalizations. The 2016 NRD includes a full calendar year of data with diagnosis and procedure codes reported using the ICD-10-CM/PCS coding system. The 2016 NRD file structure is different from the 2015 file structure, which includes both ICD-9-CM and ICD-10-CM/PCS coding. The 2016 file structure is similar to that of 2014 and earlier years, although data elements derived from AHRQ software tools are not included because the ICD-10-CM/PCS versions are still under development.

    For 2015 data, because of the transition to ICD-10-CM/PCS on October 1, 2015, data elements related to diagnoses and procedures are included in files that are split into two parts. The first 9 months of the 2015 NRD contain ICD-9-CM codes, and the last 3 months contain ICD-10-CM/PCS codes. Data elements and the data structure for the 2015 NRD have been changed. Trends based on diagnoses or procedures will be affected.

    Additional information on the NRD, including a description of data elements and summary statistics, can be found on the NRD Database Documentation page. The database can be purchased through the online HCUP Central Distributor, and select statistics from the databases are available on HCUPnet.

  • How is the NRD different from the NIS?

    The NRD and the NIS differ in design and availability of data elements. The 2016 NRD uses the SID from 27 HCUP Partners with verified patient linkage numbers and includes discharges from community hospitals, excluding rehabilitation and long-term acute care hospitals. The NIS contains a sample of records from each SID that can be weighted to represent national estimates. The NRD can be used to estimate national readmission rates for all payers and the uninsured and addresses a large gap in health care data—the lack of nationally representative information on hospital readmissions for all ages.


  • How are readmissions defined in the NRD?

    The NRD is designed to be flexible to various types of analyses of readmissions in the United States for individuals covered by all payers and the uninsured. The criteria to determine the relationship between multiple hospital admissions for an individual patient are left to the analyst using the NRD. Outcomes of interest include national readmission rates, reasons for returning to the hospital for care, and the hospital costs for discharges with and without readmissions.


  • Can I perform State-level analyses with the NRD?

    The sampling methodology used to create the NRD does not include State as a stratifier; therefore, analysts cannot use the database to generate State-level estimates. Although the NRD includes weights to allow researchers to generate national estimates from the raw counts, no weights are included for the calculation of State-level estimates.

    For information on State-specific inpatient stays, we recommend that you work with the HCUP SID.


  • Are the NRD data weighted?

    NRD data purchased through the HCUP Central Distributor include discharge weights, which the user must apply to produce national estimates. To learn how to properly weight data, consult HCUP's free online tutorial called Producing National HCUP Estimates, which describes the process of applying the weighting to your data.

    Please note that if you are using HCUPnet (our free, online query system), the weighting already has been applied—the statistics produced are national estimates.


  • How often is the NRD released, and what years are available?

    The NRD is released annually, approximately 18 to 22 months after the end of a calendar year. Data years begin with 2010. Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog.


  • Why is the file structure different in the 2015 NRD?

    Due to the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015, the file structure of the 2015 HCUP nationwide databases differs from that of the annual files for past and future years. For information on the transition to ICD-10-CM/PCS, the revised file structure in the 2015 NRD, and resources for working with the 2015 HCUP databases, please see the NRD Database Documentation page or the ICD-10-CM/PCS Resources page.


  • How much does the NRD cost?

    Complete database availability and pricing information is included in the online HCUP Central Distributor Database Catalog. Student pricing is available.

    Additionally, statistics and data tables from the NRD are available on HCUPnet, HCUP's free, online query system.
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  • What are the State databases?

    HCUP's State databases are a collection of all-payer datasets from participating States that can be used to investigate State-specific and multi-state trends in health care utilization, access, charges, quality, and outcomes. The HCUP State databases consist of the SID, the State Ambulatory Surgery and Services Databases (SASD), and the SEDD.

    A summary table shows the availability of State-level data by database and year. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog. Note that the 2015 State databases contain ICD-9-CM and ICD-10-CM/PCS codes. On October 1, 2015, hospital administrative data began using ICD-10-CM/PCS codes therefore, the first 9 months of 2015 contain ICD-9-CM codes, and the last 3 months contain ICD-10-CM/PCS codes. Data elements and the data structure for the 2015 State databases have changed. Trends based on diagnoses or procedures will be affected.

    Statistics from select States and settings are available on HCUPnet. Please review HCUPnet for a list of participating States and their years of participation.


  • Do I need to weight my State database data?

    HCUP's State databases do not need to be weighted. HCUP's State databases provide a census (not an estimate) of inpatient stays, ambulatory surgery encounters, or emergency department encounters occurring in a State's community hospitals. For additional information, please review the HCUP Methods Series Report #2010-05: Inferences With HCUP State Databases Final Report (PDF file, 215 KB).

  • If a State is an HCUP Partner, why are its databases not available through the HCUP Central Distributor or on HCUPnet?


  • HCUP Partners decide whether to distribute their State-level, public-release databases through the HCUP Central Distributor and whether to distribute statistics on HCUPnet. As a result, data from any given State may be available through one or both sources, and the years of participation can vary.

    A summary table shows State participation in the HCUP Central Distributor by database and year. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog. HCUPnet provides a list of the available State statistics and years included in the query system on the State statistics pathways.

    If a State of interest does not release its full dataset through the HCUP Central Distributor or participate in HCUPnet, contact the HCUP Partner directly for information about the availability of that State's data.

  • When are the State databases generally released?

    HCUP's State databases (SID, SASD, and SEDD) are released on a rolling basis—typically beginning 6 to 9 months following the end of a calendar year.

    A summary table shows the availability of State-level data by database and year. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog. Recent releases also are noted on a monthly basis in the HCUP Database and Product Releases Calendar.
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  • What are the State Inpatient Databases (SID)?

    The SID are a set of all-payer inpatient care databases from participating HCUP Partners that capture hospital inpatient stays in a given State. They contain the universe of inpatient discharge abstracts in participating States that are translated into a uniform format to facilitate multi-state comparisons and analyses. The SID contain a core set of clinical and nonclinical information on all patients, regardless of payer, including individuals covered by Medicare, Medicaid, private insurance, and the uninsured.

    Together, the SID encompass about 97 percent of all U.S. community hospital discharges.

    The SID are the building blocks of the National Databases NIS, the KID, the NRD, and the NEDS. All SID include a core set of variables that commonly are included on inpatient discharge abstracts, along with some State-specific data elements.

    The 2015 SID contain ICD-9-CM and ICD-10-CM/PCS codes. On October 1, 2015, hospital administrative data began using the ICD10-CM/PCS coding system, so the first 9 months of 2015 contain ICD-9-CM codes, whereas the last 3 months contain ICD-10-CM/PCS codes. Data elements andthe data structure for the 2015 SID have changed. Trends based on diagnoses or procedures will be affected.

    Additional information on the SID, including a description of data elements with participation by State and year and summary statistics for select States, can be found on the SID Database Documentation page. Select SID can be purchased through the HCUP Central Distributor, and statistics from select States are available on HCUPnet.


  • What is the difference between the SID and the NIS?

    The SID and the National Inpatient Sample (NIS) differ in design and availability of data elements. The SID contain the universe of the inpatient discharge abstracts in participating States. The NIS contains a sample of records from each SID that can be weighted to represent national estimates. Key differences exist between the SID and the National Inpatient Sample (NIS). Foremost, each SID contains the universe of inpatient discharge abstracts provided by an HCUP State Partner, whereas the NIS consists of a sample of discharges provided by all HCUP State Partners. Additionally, the NIS contains fewer data elements than the SID. The common data elements in the SID become the NIS core data elements and are standardized.


  • What years of the SID are available, and how much do they cost?

    The availability and cost of the SID vary by State and year. The earliest available SID begin in 1990; however, not all States provide data from every year. Each HCUP Partner sets its own pricing, and some charge by applicant affiliation. A summary table shows the availability of State-level data by database and year. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog.

    Additionally, statistics and data tables from select SID are available on HCUPnet, HCUP's free, online query system.

    Many HCUP Partners participate in the HCUP Central Distributor and HCUPnet; however not all do. To obtain State-level data from a State that does not participate, contact the HCUP Partner directly for information on the availability of that State's data.


  • Why is the file structure different in the 2015 SID?

    Due to the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015, the file structure of the 2015 HCUP State databases differs from the structure of the annual files for past and future years. For information on the transition to ICD-10-CM/PCS, the revised file structure in the 2015 SID, and resources for working with the 2015 HCUP databases, please see the SID Database Documentation page or the ICD-10-CM/PCS Resources page.
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  • What are the State Ambulatory Surgery and Services Databases (SASD)?

    The SASD include encounter-level data for ambulatory surgeries and also may include data on various types of outpatient services such as observation stays, lithotripsy, radiation therapy, imaging, chemotherapy, and labor and delivery. The specific types of ambulatory surgery and outpatient services included in each SASD vary by State and data year. All SASD include data from hospital-owned ambulatory surgery facilities. In addition, some States include data from facilities not owned by a hospital. The designation of a facility as hospital-owned is specific to its financial relationship with a hospital that provides inpatient care and is not related to its physical location. Hospital-owned ambulatory surgery and other outpatient care facilities may be contained within the hospital, physically attached to the hospital, or located in a different geographic area.

    The 2015 SASD contain ICD-9-CM and ICD-10-CM/PCS codes. On October 1, 2015, hospital administrative data began using the ICD-10-CM/PCS coding system, so the first 9 months of 2015 contain ICD-9-CM codes, whereas the last 3 months contain ICD-10-CM/PCS codes. Data elements and the data structure for the 2015 SASD have changed. Trends based on diagnoses or procedures will be affected.

    Additional information on the SASD, including a description of data elements with participation by State and year and summary statistics for select States, can be found on the SASD Database Documentation page. Select SASD can be purchased through the HCUP Central Distributor, and statistics from select States are available on HCUPnet.


  • What types of facilities are included in the SASD?

    All SASD include data from hospital-owned ambulatory surgery facilities. In addition, some States include data from nonhospital-owned facilities. The designation of a facility as hospital-owned is specific to its financial relationship with a hospital that provides inpatient care is not related to its physical location. Hospital-owned ambulatory surgery and other outpatient care facilities may be contained within the hospital, physically attached to the hospital, or located in a different geographic area. The designation as hospital-owned means that HCUP can identify that the hospital is billing for this service. A complete list of the types of facilities included in the SASD can be found on the SASD File Composition page.


  • What years of the SASD are available, and how much do they cost?

    The availability and cost of the SASD vary by State and by year. The earliest available SASD begin in 1997; however, not all States provide data from every year. Each HCUP Partner sets its own pricing, and some charge by applicant affiliation. A summary table shows the availability of State-level data by database and year. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog.


  • Why is the file structure different in the 2015 SASD?

    Due to the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015, the file structure of the 2015 HCUP State databases differs from that of the annual files for past and future years. For information on the transition to ICD-10-CM/PCS, the revised file structure in the 2015 SASD, and resources for working with the 2015 HCUP databases, please see the SASD Database Documentation page or the ICD-10-CM/PCS Resources page.


  • What is the difference between the State Ambulatory Surgery Databases (for years prior to 2014) and the State Ambulatory Surgery and Services Databases (for 2014 onward)?

    The State Ambulatory Surgery and Services Database replaces the State Ambulatory Surgery Databases for years starting 2014. The only difference between the two databases is the name and both are referred to as SASD. The name State Ambulatory Surgery and Services Databases (SASD) better describes the current and historical content. There is no difference in the sampling or variables available in the SASD database before and after the name change.

    The HCUP team has endeavored to better understand the types of data and utilization that are included in the State Ambulatory Surgery Databases (SASD). We completed a rigorous review of all documentation that is provided by our HCUP Partners, supplemented by phone conversations with each of the Partner data organizations that provide State Ambulatory Surgery Databases data to HCUP. It is clear that for most of our Partners, the State Ambulatory Surgery Databases include data for outpatient ambulatory surgery as well as other hospital-based outpatient services. Some of our HCUP Partners also provide ambulatory surgery data and outpatient care services from nonhospital-owned facilities. Therefore, we have updated the name of the databases to the State Ambulatory Surgery and Services Databases (the acronym SASD will stay the same) and updated all documentation on HCUP-US to better communicate what is included in these databases. Visit the SASD Overview page for additional information.
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  • What are the State Emergency Department Databases (SEDD)?

    The SEDD are a set of all-payer emergency department (ED) databases from participating HCUP Partners that capture discharge information on all ED encounters that do not result in an admission to the same facility. They include a universe of abstracts from hospital-affiliated ED encounters from community hospitals. Composition and completeness of the variables in the file may vary from State to State. The SEDD contain a core set of clinical and nonclinical information on all patients, regardless of payer, including individuals covered by Medicare, Medicaid, private insurance, and the uninsured.

    The 2015 SEDD contain ICD-9-CM AND ICD-10-CM/PCS codes. On October 1, 2015, hospital administrative data began using ICD10-CM/PCS, so the first 9 months of 2015 contain ICD-9-CM codes, whereas the last 3 months contain ICD-10-CM/PCS codes. Data elements and the data structure for the 2015 SEDD have changed. Trends based on diagnoses or procedures will be affected.

    Additional information on the SEDD, including a description of data elements with participation by State and year and summary statistics for select States, can be found on the SEDD Database Documentation page. Select SEDD can be purchased through the HCUP Central Distributor, and statistics from select States are available on HCUPnet.


  • Do the SEDD include all ED encounters—both those in which the patient was admitted and those in which the patient was treated and released?

    No. The SEDD provide encounter-level information for ED encounters that do not result in an admission to the same facility (i.e., patients in the SEDD were treated and released). Records for inpatient stays that began in the ED are found in the SID. Both the SEDD and SID are needed to analyze all ED encounters in a State.


  • What years of the SEDD are available, and how much do they cost?

    The availability and cost of the SEDD vary by State and by year. The earliest available SEDD begin in 1999; however, not all States provide data from every year. Each HCUP Partner sets its own pricing, and some charge by applicant affiliation. A summary table shows the availability of State-level data by database and year. Complete database availability and pricing information is provided in the online HCUP Central Distributor Database Catalog.

    Additionally, statistics and data tables from select SEDD are available on HCUPnet, HCUP's free, online query system.

    Many HCUP Partners participate in the HCUP Central Distributor and HCUPnet; however, not all do. To obtain State-level data from a State that does not participate, contact the HCUP Partner directly for information about the availability of that State's data.


  • Why is the file structure different in the 2015 SEDD?

    Because of the transition from ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures on October 1, 2015, the file structure of the 2015 HCUP State databases differs from that of annual files for past and future years. For information on the transition to ICD-10-CM/PCS, the revised file structure in the 2015 SEDD, and resources for working with the 2015 HCUP databases, please see the SEDD Database Documentation page or the ICD-10-CM/PCS Resources page.
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  • How can I access data or statistics from HCUP?

    The HCUP databases are available for purchase online through the HCUP Central Distributor. All purchasers must complete the online DUA training and create an HCUP user account in order to submit an application to purchase HCUP data. Please see Purchasing FAQs for additional information.

    Statistics and data tables from HCUP's nationwide and select State databases can be obtained from HCUPnet, a free, online query system. Statistics and data tables on select topics are also available through HCUP Fast Stats.

    HCUP is a voluntary partnership between the Federal government and State data organizations (HCUP Partners). Each Partner determines how its data are used in HCUP; thus, not all States participate in the Central Distributor, HCUPnet, and/or Fast Stats.


  • Can I obtain a customized dataset or access additional elements that are not included in the standard HCUP databases?

    HCUP does not offer customized datasets—the data are offered as standard databases. No elements beyond those that already are included in the standard databases are available to the public.


  • How can I get help loading or unzipping files I purchased?

    If you would like assistance with loading files, unzipping files, and using passwords to start working with the databases purchased from HCUP, you may contact the HCUP Central Distributor support at HCUPDistributor@ahrq.gov.
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This section of the HCUP-US Frequently Asked Questions provides information about HCUP database purchases, current HCUP database orders and invoices, downloading Nationwide HCUP databases, unzipping HCUP State or Nationwide database products, and the submission of required HCUP Data Use Agreements (DUAs), training certificate codes, and data re-use requests to the HCUP Central Distributor.

  • How do I contact the HCUP Central Distributor?

    E-mail: HCUPDistributor@ahrq.gov (include order number in Subject line if applicable)
    Phone: 866-556-HCUP (4287) (toll free)
    Fax: 866-792-5313 (toll free in the United States)

    Mailing address:
    HCUP Central Distributor
    Social & Scientific Systems, Inc.
    8757 Georgia Ave, 12th Floor Silver Spring, MD 20910


HCUP Databases for Purchase

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  • Where do I log in to my HCUP account?

    If you are an HCUP data purchaser, the online HCUP Central Distributor page contains links to log in, view your account, check the status of data purchase applications, and/or download your purchased Nationwide Databases.


  • Is an HCUP account required to place an order?

    Yes, you must have an account with the online HCUP Central Distributor to place an order. You can browse the database catalog of HCUP databases and add items to your shopping cart without an account; however, you cannot proceed to checkout without logging in to your account. The online HCUP Central Distributor page provides links to register, log in, view your account, and shop for database


  • How do I set up an HCUP account?

    • Take the required online Data Use Agreement (DUA) training. Document the certification code provided upon completion and the completion date. This information will be required to set up your account. For current requirements see "Why is Data Use Agreement (DUA) training required for account setup?"

    • Register for an account with the online HCUP Central Distributor. You will be asked to establish a unique username (your email address) and password.

    • Login on the online HCUP Central Distributor page and complete your profile under My Account, including your DUA training certification code and completion date.


  • Why is Data Use Agreement (DUA) training required for account setup?

    All purchasers and users of HCUP data must complete the online Data Use Agreement (DUA) training so that they are familiar with the rules and restrictions for use of HCUP data. It is imperative to understand how the data may be used before placing your order or gaining access to HCUP data. You will be required to acknowledge that you have read, understand, and agree to comply with the terms of the DUAs, the Responsibilities of the Data Purchaser (PDF file, 33 KB), and an Indemnification Clause before submitting your order.

    If you are a long-time user of HCUP databases and your DUA training code is in the format "HCUP-XXXX-XXX" where "X" is a letter or digit, we ask that you retake this training to obtain a new certification code. The online system will only accept current certification codes. New users will not be required to take the course more than once.


  • Can I set up an account and order databases on someone else's behalf?

    The data purchaser takes full responsibility for complying with all terms of the Data Use Agreement. Consequently, the account holder cannot order databases for, or ask the Central Distributor to ship databases to, someone else. Databases must be received by the data purchaser who is responsible for the data.

    Under the terms of the DUA, the data purchaser remains responsible for the security and use of the HCUP data unless and until custody of the data is officially transferred to another individual. This and other Responsibilities of the Data Purchaser (PDF file, 33 KB) are acknowledged during database purchase. To transfer custody of HCUP databases, the original data purchaser must agree to relinquish their rights to the data and the new data custodian must complete the DUA training course; read, sign, and submit the appropriate HCUP DUA; and agree to take full responsibility of the HCUP databases as described in the DUA. To request a transfer of custody contact the HCUP Central Distributor.


  • Are other persons working on my study required to submit a Data Use Agreement?

    Yes. Anyone with access to HCUP data or access to results from the data that contain sensitive information (such as information by individual hospitals or aggregated statistics with small cell sizes) must complete the HCUP Data Use Agreement (DUA) Training Course and sign the DUA for Nationwide and/or State Databases. Both the signed DUA(s) and the DUA Training Course completion certificate (or certification code) must be submitted to the HCUP Central Distributor before any collaborator can be granted access to the data.


  • How do I submit my Data Use Agreement?

    Data Purchasers:
    Data users purchasing HCUP databases and supplemental files through the online HCUP Central Distributor will execute their DUAs electronically during the ordering process. Purchasers must review and acknowledge the DUA to place an order. A copy of the executed DUA will be available under My Account. Please note that users are required to sign and submit a Nationwide and/or State DUA each time they complete a new application to purchase HCUP databases.

    Others with Access to HCUP Data:
    Anyone with access to HCUP data must take the HCUP Data Use Agreement (DUA) Training Course and submit proof of training with the appropriate DUA(s) prior to gaining access to the data. The following options for submitting DUAs are detailed on the Data Use Forms & Agreements tab in the online HCUP Central Distributor.
    • DUAs can be electronically acknowledged and submitted in the online HCUP Central Distributor by data users with proof of DUA training. A copy of the executed DUA will be available under My Account.
    • If you will be working on a specific project, ask your data custodian (the person whose data you'll access) to issue you an electronic invitation to submit the DUAs online through the Central Distributor. Using the invitation will streamline the online DUA submission process and ensure your DUAs are associated with the correct data custodian.
    • If you cannot access the online HCUP Central Distributor, proof of training and signed DUAs may be submitted by fax or postal service.


  • How do my collaborators submit their signed Data Use Agreements (DUAs) and DUA training certificates?

    Before you may share your HCUP data with anyone, they must complete the HCUP Data Use Agreement (DUA) Training Course and read and sign the applicable Nationwide and/or State DUA(s) found on the DUA Training page. These documents must be submitted to the HCUP Central Distributor before you grant access to the HCUP databases.

    The following options for submitting DUAs are detailed on the Data Use Forms & Agreements tab in the online HCUP Central Distributor:
    • DUAs can be electronically acknowledged and submitted in the online HCUP Central Distributor by data users with proof of DUA training. A copy of the executed DUA will be available under My Account.
    • You may issue invitations to your data users to streamline the online submission process, using the online HCUP Central Distributor under the DUAs tab in My Account.
    • If your data user cannot access the online HCUP Central Distributor, proof of training and signed DUAs may be submitted by fax or postal service.


  • Is a Data Use Agreement different from a Statement of Intended Use, and do I need both?

    The Nationwide and State Data Use Agreements define the rules and limitations under which any HCUP data may be used; a DUA is required for every person with access to the data regardless of the nature of the project.

    State-level HCUP data also requires a Statement of Intended Use (PDF file, 45 KB) which defines your specific project plans. AHRQ and the HCUP Central Distributor facilitate access to the State-level HCUP data (i.e., SID, SASD and SEDD), which are owned and regulated by the individual Data Organizations participating in HCUP. Under AHRQ's agreements with these Data Organizations, AHRQ reviews and approves all intended uses of the State-level data on their behalf. See "Why am I being asked to provide a Statement of Intended Use and what should I include in my Statement?" for more information.

  • Can I re-use my HCUP State data for a new project?

    Each application for and approval of HCUP data is project-specific. If the data will be used for a purpose other than that originally approved, or as concrete projects emerge from approved exploratory work, the data custodian must submit a "Data Re-use Request" (PDF file, 47 KB) to the HCUP Central Distributor for review and approval by AHRQ before work may begin on the new project.

  • If I change my email address, will my HCUP account Username change too?

    If you need to change your email address, you may do so without affecting the original Username that was set up when you registered with the online HCUP Central Distributor. Your email address can be updated in your User Information under My Account, and can also be updated while confirming your Applicant Information during order checkout. Your Username will not change.
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  • How long will items be saved in my shopping cart?

    Items will be saved in your online HCUP Central Distributor shopping cart for 30 days. After 30 days, items will be automatically removed from your cart.


  • Why am I being asked to provide a Statement of Intended Use and what should I include in my Statement?

    A Statement of Intended Use (PDF file, 45 KB) is required if you requested the SID, SASD, and/or SEDD files from the HCUP Central Distributor. This Statement is reviewed by AHRQ on behalf of the HCUP Partners. It should include enough information for reviewers to understand the subject area of interest, how the data will be used, intended audiences, and anticipated end-products (e.g., tables and charts, internal reports, peer-review journal articles), as well as to assess compliance with the HCUP Data Use Agreement (DUA) for State Databases (PDF file, 53 KB). In some cases, the HCUP Partners also review the Statement of Intended Use before approval is granted, and in all cases, orders that include State Databases are provided in full to the respective data organizations.

    The AHRQ reviewers will place your application on hold and request clarification from you if your Statement of Intended Use is insufficient for review and approval.


  • How can I view the Statement of Intended Use for my State Database order?

    You can view all order details, including the Statement of Intended Use, by logging in to the online HCUP Central Distributor and selecting Orders under My Account. The Statement of Intended Use will also appear on the copy of your invoice that is included in each email you receive from the HCUP Central Distributor as your order is processed.

    Please note that if the Statement of Intended Use that you submit with your order does not provide enough information for the AHRQ reviewers to understand how the data will be used and reported, the HCUP Central Distributor will contact you by email to request more details.
    • For applications submitted after October 17 2018, if AHRQ requires further clarification of your Statement of Intended Use, you will be instructed via email to log in to the online HCUP Central Distributor to revise and resubmit the Statement of Intended Use. The Statement of Intended Use viewed in your order details will reflect your revisions and AHRQ's project-specific approval when applicable.
    • For orders submitted prior to October 17, 2018, any email or telephone communications that further clarified the scope of the project and use of the HCUP data are not reflected in the static Statement of Intended Use captured with the original application, but nonetheless are deemed to govern and/or limit the extent of the approved use of the data.


  • Can I place an order without electronically acknowledging the Data Use Agreement(s) (DUA), Responsibilities of the Data Purchaser, and Indemnification Clause?

    Every order requires the data purchaser to read and agree to the terms of the Data Use Agreement(s) (DUAs), Responsibilities of the Data Purchaser, and Indemnification Clause. If you place your order online, you must execute these agreements electronically as a part of the checkout process; you will not be able to complete your order without doing so. These executed documents are retained by the HCUP Central Distributor and may be accessed by logging in to the online HCUP Central Distributor and selecting Orders under My Account.

    If you or your institution requires a physically signed DUA, you will need to submit a hard copy application for your order. Hard copy Application Kits are available on the HCUP-US Web site or by contacting the HCUP Central Distributor.

  • How do I print my order invoice and acknowledged Data Use Agreement(s), Responsibilities of the Data Purchaser, and Indemnification Clause?

    You can view and print all your order details including your invoice, Statement of Intended Use, acknowledged Data Use Agreement(s), Responsibilities of the Data Purchaser, and Indemnification Clause by logging in to the online HCUP Central Distributor and selecting Orders under My Account.


  • Why can't I have the data delivered to someone else?

    The account holder takes full responsibility for complying with all terms of the Data Use Agreement and the Responsibilities of the Data Purchaser (PDF file, 33 KB). HCUP data may only be delivered to (i.e., shipped to or downloaded by) the individual who places the order through their account. Consequently, the account holder cannot order databases for, or authorize their delivery to, someone else. See "Can I set up an account and order databases on someone else's behalf?" for more information.


  • How can I tell if my order was received?

    When you are completing your HCUP database order in the online HCUP Central Distributor, after selecting "Order now" to submit your order, you will be directed to a "Thank you" page explaining what to expect in the order fulfillment process.

    You will receive follow-up emails from the HCUP Central Distributor (Do-Not-Reply-HCUPDistributor@s-3.com) containing your order invoice, order status updates, and all necessary instructions for order fulfillment.


  • How long will it take to receive the HCUP database(s) I ordered?

    HCUP Nationwide Databases (NIS, KID, NEDS, and NRD) and related Supplemental Files are delivered via digital download, and can be downloaded from your Orders page in the online HCUP Central Distributor after your order is complete. You will receive an email alerting you when your files are ready for download. Please be aware that download links are active for only 7 days.

    HCUP State Databases (SID, SASD, and SEDD) and related Supplemental Files are shipped on CD/DVD, typically within 5-7 business days after the Agency for Healthcare Research and Quality (AHRQ) reviews and approves the Statement of Intended Use (PDF file, 45 KB) on behalf of the HCUP Partners. In some cases, additional review by the Partner organization will be required and may increase the time needed to respond to applications. The HCUP Central Distributor uses FedEx Standard Overnight service. An adult signature is required to receive the package. You will receive emails from FedEx when the package ships and when it has been delivered.

    Orders cannot be partially fulfilled. If your order includes both Nationwide and State Databases, the Nationwide Databases will not be available for download until AHRQ approves your request for the State Database(s). In order to facilitate your receipt of the Nationwide Databases, please consider placing separate orders for Nationwide versus State files.


  • If I submit separate orders for Nationwide Database(s) and State Databases, can I download the Nationwide Databases sooner?

    Yes. If you will be applying for both State and Nationwide Databases, you may facilitate your receipt of the Nationwide Databases if you place a separate order for Nationwide versus State files. This will allow the Nationwide Database(s) and related Supplemental Files to be downloaded as soon as your Nationwide order is complete.


  • How can I check the status of my order?

    Orders are processed after payment and any applicable documentation (such as verification of eligibility for student pricing) are received by the HCUP Central Distributor. You will receive email status updates.

    To check the status of your order, log in to the online HCUP Central Distributor and select Orders under My Account. The current status of your order is displayed. If you have questions about the status, you can view the order details for additional information or contact the HCUP Central Distributor.

    If you paid by credit card, please note that credit card authorization expires after 30 days. Your card will not be charged until the databases are shipped or activated for download. Orders that include State Databases or discount pricing require time for review and processing, and may require additional action on your part. Please respond promptly to any inquiry from the HCUP Central Distributor regarding your order.


  • How do I change or cancel my order?

    For any changes or to cancel your order, you must contact the HCUP Central Distributor. Please include your order number for reference. The order number is in the Subject Line of each email you've received from the HCUP Central Distributor, and can be viewed under Orders in My Account in the online HCUP Central Distributor.
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  • Why are there different price categories for many HCUP databases?

    The HCUP Nationwide Databases (NIS, KID, NEDS, and NRD) are offered at a discounted price for students. In addition, several States offer student prices for their HCUP State Databases (SID, SASD, and SEDD).

    Part-time and full-time students at any stage in their training are eligible for the published student prices on HCUP data purchased for the student's exclusive use. However, all students must demonstrate their current student status by providing: (1) a copy of a valid student ID, OR (2) a letter from the registrar's office, a professor advisor, or the program director. This information will be requested after you place your order online and should be submitted to the HCUP Central Distributor. See "If an HCUP dataset is purchased at student pricing for a student/faculty project, is the faculty member allowed to continue using the database after the student leaves?" for more information

    Some States also offer other pricing categories such as nonprofit affiliations and AHRQ grantees. If your order is based on these pricing categories, you may be asked to provide documentation of affiliation or AHRQ grant status before your order may be fulfilled.


  • Will I be charged for shipping costs?

    Shipping and handling costs are included in the price of the databases. Customs and other duty charges for overseas delivery are not included. The HCUP Central Distributor does not calculate or collect duties or overseas taxes.


  • Will taxes be applied to my order?

    The HCUP Central Distributor will collect applicable State sales tax on orders shipped to Maryland and North Carolina. Individuals shipping to all other locations are responsible for determining tax liability and remitting taxes directly to State and local taxing authorities.


  • What payment methods are accepted?

    The HCUP Central Distributor accepts payments from MasterCard and Visa, bank check, purchase order, or wire transfer.

    Orders must include full payment or credit card authorization; databases will not be shipped until payment is received.

    The order number or a copy of the invoice must be included with payment.

    • If payment is made online by credit card, your card will not be charged until the database(s) are shipped or activated for download. Credit card authorization expires after 30 days; please respond promptly to any inquiry from the HCUP Central Distributor regarding your order.
    • Checks should be payable and mailed to Social & Scientific Systems, Inc.
    • Purchase orders may be paid by check or credit card. Please contact the Central Distributor by phone, fax, or mail; do not email credit card information.
    • Wire transfer information may be submitted to the Central Distributor by phone, fax, or mail. Do not email wire transfer information.


  • Does the HCUP Central Distributor retain my credit card information?

    No, the HCUP Central Distributor does not retain credit card information; only the card authorization is saved. Authorize.net Exit Disclaimer is used as the payment gateway for processing credit card transactions. Authorize.net is on Visa's Global List of Payment Card Industry Data Security Standard (PCI DSS) Validated Service Providers. Exit Disclaimer For credit card processing, only TransactionID and Authorization Code from Authorize.net are stored.

    Credit card authorization expires after 30 days; please respond promptly to any inquiry from the HCUP Central Distributor regarding your order.


  • If an HCUP dataset is purchased at student pricing for a student/faculty project, is the faculty member allowed to continue using the database after the student leaves?

    No, student purchases of HCUP data are specific to the student, are intended for student-directed projects (e.g., dissertation), and the student is responsible for the security and all uses of the data. Faculty may be involved with the student's project (e.g., faculty advisor) and have access to the data as long as they have completed the online HCUP Data Use Agreement training, read and signed the Data Use Agreement, and submitted the training certification code and Data Use Agreement to the HCUP Central Distributor, but student priced data is not intended for faculty-led projects in which the student is participating.

    Further, when the student leaves the university, the student shall take the data with him/her; no one else is allowed independent access. A faculty member can have continued access to the data only if he or she continues to have a professional relationship with the student (e.g., co-authorship or joint project). In that case, the student must agree to this collaboration because the student is held responsible for the data.
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  • Where do I go to download the Nationwide Database files I purchased?

    HCUP Nationwide Databases (NIS, KID, NEDS, and NRD) and related Supplemental Files are delivered via digital download, and can be downloaded from your Orders page in the online HCUP Central Distributor after your order is complete. Please be aware that download links are active for only 7 days.


  • How long will it take to download the Nationwide Databases I purchased?

    Download performance depends on several highly variable factors, including:

    • Your internet connection speed and bandwidth
    • Global and regional internet traffic demand at the time of your download
    • Other users' demand on your network or internet service provider (ISP) resources at the time of your download

    In download performance trials from various locations across the US and UK, most test users completed a 1500 MB download in 10-20 minutes. The fastest networks download this large file in 3-8 minutes; the slowest download took 3 hours. Each user found the time to vary significantly between tests, depending on variable environmental factors.

    For optimal download performance, try to control the following variables to the extent possible:

    • Use a wired connection (e.g., Ethernet cable) if possible. Wired is much faster than wireless on the same network/internet service.
    • Avoid 'Sleep' mode: Make sure your computer is not set to go to sleep. The download will be paused if your computer goes to sleep, but can be resumed upon waking.
    • Use times of low demand on your network or local internet service provider (e.g., at work, try the download in the evening; at home, avoid evenings when other users of your ISP are likely to be online).
    • Avoid high-demand sites or activities on your computer during the download.
    • Avoid VPN: If you use VPN (Virtual Private Network) to connect to a secure work environment, but could connect to the online Central Distributor Web site directly (using a secure private/home or work network) while VPN is not running, do so. VPN significantly slows download speeds.

    You can check your internet connection speed/bandwidth at a given point in time using a site such as Bandwidth Place. Exit Disclaimer Typical benchmarks have been:

    • Wired, no VPN: 26 MB per second
    • Wireless, no VPN: 18 MB per second
    • VPN, wired or wireless: 3 MB per second


  • Is the database download process secure?

    Yes. You must be logged in to your account in the online HCUP Central Distributor in order to initiate a download of purchased files under Orders. The site uses SSL (secure socket layer) protocol, and therefore as long as you are using a secure network at work or home to log in, the download is secure. In addition, the files are compressed using an encrypted "zip" method, and can only be unzipped using a password. However, as with any other internet activity involving private or restricted information, the download should not be performed over a public network.


  • My download did not successfully complete and/or my download link is not working. What should I do?

    For Nationwide Databases you have purchased, each download link in your order in the online HCUP Central Distributor is valid for 7 days and is limited to 3 download attempts. If your download link has expired, you have received an error message indicating there was a problem with the download, or you have experienced any other problem preventing you from successfully downloading your products, please contact the HCUP Central Distributor for assistance in identifying and resolving the problem.

    Please make every effort to seek assistance before your download link expires.


  • How can I tell if the file is downloading?

    The "Download" link initiates the browser's download widget, so the appearance and behavior of the download depends entirely upon the internet browser you are using.

    To facilitate the process in any browser, if you are prompted to choose between Save and Open, choose Save. Be sure to save to a location that has enough space to hold the file(s) you are downloading. Some browsers may simply default to a Downloads folder or comparable default location. Some browsers have highly visible download prompting and progress displays, while other browsers may use download defaults and/or subtle progress displays. It is up to the user to be familiar with the download behaviors of the chosen internet browser.

    Contact the HCUP Central Distributor for assistance if you are unable to verify a successful download.


  • Do I need special software to unzip the downloaded file?

    Yes. HCUP Databases use a process that compresses and encrypts the files into a password-protected zip file that can only be unzipped using a third-party Zip utility such as ZIP Reader, SecureZIP, WinZip, etc. Attempts to unzip files using the built-in zip utilities in Windows (Windows Explorer) or Mac (Archive Utility) will produce an error message warning of incorrect password and/or file or folder errors.

    Third-party zip utilities are available from the following reputable vendors on their official Web sites.

    • ZIP Reader (Windows) (free download offered by the PKWARE corporation)
    • SecureZIP® for Mac (free evaluation and licensed/fee software offered by the PKWARE corporation)
    • WinZip (Windows) (evaluation and fee versions offered by the WinZip corporation)
    • Stuffit Expander® (Mac) (free evaluation and licensed/fee software offered by Smith Micro corporation
    • 7-Zip (Windows) (free download offered by the 7-Zip organization)


  • Where do I find the password for downloaded files?

    When your order for HCUP Nationwide Databases is activated for download, you will receive follow-up emails from the HCUP Central Distributor (Do-Not-Reply-HCUPDistributor@s-3.com) containing your order invoice, order status updates, and all necessary instructions for order fulfillment including the passwords for purchased files.


  • How much space will the downloaded file(s) require?

    The size of each purchased file will be listed in your order in the online HCUP Central Distributor on the Database Downloads page. The database files are compressed, and range from 300 MB to 2 GB when downloaded, as shown in the table below.

    Each product you download will contain several files when unzipped, including the core database file in comma-delimited format, plus additional support files such as database documentation. The amount of space required to unzip each database product is shown in the table below, based on the largest year of data for each database type.

    Database Download (zip) size Unzipped size
    NIS 760 MB 6 GB
    KID 300 MB 3 GB
    NEDS 2 GB 20 GB
    NRD 2 GB 20 GB

    Please note that you will need SAS®, SPSS®, Stata® or similar analysis software for processing the data, and all such processing requires several times as much disc capacity as the core file, in order to perform typical processing steps. Due to variations in processing methods, analysis software varies greatly in how much disc space will required. The amount of disc space required by your project will depend upon which analysis software you are using, which database is involved, and the number of elements you use from the database.

    To determine minimum data analysis space requirements, please refer to the documentation for each specific database you will be working with. Database documentation is supplied in each zipped product file, and can also be found on HCUP-US on the Databases page.


  • I already own a Nationwide Database. May I use the download feature to access the file?

    The download link is only active for 7 days after you receive notification that your newly purchased Nationwide products are ready to download. You must arrange to store your downloaded products securely for your future use.
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  • I didn't purchase data but will be collaborating on a project with the data purchaser or otherwise have access to HCUP data. Do I need to submit a Data Use Agreement?

    Everyone with access to HCUP data must take the HCUP Data Use Agreement (DUA) Training Course and submit proof of training with the appropriate DUA(s) prior to gaining access to the data. If you are not the original data purchaser or data custodian, your DUA should be associated with the individual whose data you may access. The following options for submitting DUAs are detailed on the Data Use Forms & Agreements tab in the online HCUP Central Distributor:

    • DUAs can be electronically acknowledged and submitted in the online HCUP Central Distributor by data users with proof of DUA training. A copy of the executed DUA will be available under My Account.
    • If you will be working on a specific project, ask your data custodian (the person whose data you'll access) to issue you an electronic invitation to submit the DUAs online through the Central Distributor. Using the invitation will streamline the online DUA submission process and ensure your DUAs are associated with the correct data custodian.
    • If you cannot access the online HCUP Central Distributor, proof of training and signed DUAs may be submitted by fax or postal service.
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To enhance the capabilities of the HCUP databases, HCUP provides a number of tools and software programs that can be applied to HCUP and other similar administrative databases. Many are available for download from the HCUP-US Web site. Others may be ordered through the online HCUP Central Distributor. All of HCUP's tools and software products are free-of-charge. *Most HCUP Tools have been translated to ICD-10-CM/PCS. The tools will undergo periodic updates, and tools associated for ICD-10-CM/PCS are considered Beta products.

For information on the transition to ICD-10-CM/PCS, the revised file structure in the 2015 HCUP databases, and resources for working with the 2015 HCUP databases, please see the ICD-10-CM/PCS Resources page.
  • What is the Clinical Classification Software (CCS)?

    The CCS is a categorization scheme that was developed by AHRQ. It can be used to classify similar diagnosis or procedure coding (such as ICD-9-CM or ICD-10-CM/PCS codes) and collapse them into a smaller number of clinically meaningful categories. The CCS categories may be more useful for presenting descriptive statistics than for presenting individual codes.


  • What types of CCS tools are there?

    There are three types of CCS tools. The CCS for ICD-9-CM provides a diagnosis and procedure categorization scheme that can be used to classify more than 14,000 ICD-9-CM diagnosis and 3,900 procedure codes into a smaller number of clinically meaningful categories.

    The Beta CCS for ICD-10-CM/PCS clusters more than 69,800 ICD-10-CM diagnosis and 71,900 ICD-10-PCS procedure codes into a manageable number of clinically meaningful categories that are sometimes more useful for presenting descriptive statistics than are individual ICD-10-CM/PCS codes. The official implementation of ICD-10-CM/PCS took place on October 1, 2015.

    • Caution: These ICD-10-CM/PCS tools were created prior to the availability of ICD-10-CM/PCS-coded data. AHRQ is conducting analyses of ICD-10-CM/PCS data; preliminary findings suggest some unexpected discontinuities between the tools based on ICD-9-CM and those based on ICD-10-CM/PCS. See www.hcup-us.ahrq.gov/datainnovations/icd10_resources.jsp for details. The tools will undergo periodic updates and corrections as data using ICD-10-CM/PCS codes come into greater use. You are advised to visit this page regularly to download and apply the most recent version of the HCUP tools for your data throughout your research process.

    The CCS-for Services and Procedures-(CCS-Services and Procedures) provides a method for classifying Current Procedural Terminology (CPT®) codes and Healthcare Common Procedure Coding System (HCPCS) codes into clinically meaningful procedure categories. The procedure categories are identical to the CCS for ICD-9-CM, with the addition of specific categories unique to professional service and supply codes in CPT/HCPCS. Before downloading the CCS-Services and Procedures, users must agree to a license agreement with the American Medical Association for using CPT codes.


  • Will the transition from ICD-9-CM to ICD-10-CM/PCS coding impact the 2015 HCUP databases?

    For information on the transition to ICD-10-CM/PCS and resources for working with the 2015 HCUP databases, please see the ICD-10-CM/PCS Resources page.


  • How often is the CCS updated?

    The Beta CCS for ICD-10-CM/PCS and the CCS-Services and Procedures are updated annually, as ICD-10-CM/PCS, CPT, and HCPCS codes are revised. Updates typically are released between October and April, and the software is valid for codes from January 1, 1980, through September 30 of the designated fiscal year.


  • How can I obtain the CCS, and how much does it cost?

    The CCS may be downloaded free of charge from the HCUP-US Web site. Select the type of CCS tool in which you are interested, and click on the Downloading Information link.
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  • What are the Cost-to-Charge Ratio Files (CCR Files)?

    The CCR Files are linkable files developed by the AHRQ that enable the conversion of total charges—defined as what the amount a hospital billed for services —into how much the hospital services actually cost.

    Each CCR File contains hospital-specific cost-to-charge ratios based on all-payer inpatient cost for nearly every hospital in the corresponding SID, NIS, KID, and NRD. Cost information was obtained from the hospital accounting reports collected by the Centers for Medicare & Medicaid Services (CMS). Some imputations for missing values were necessary.


  • Which databases have CCR Files?

    The CCR Files are designed to be used exclusively with the SID, the NIS, the KID, and the NRD and are unique by year. The CCR Files are not available for the NEDS, SASD, or SEDD.


  • How often are the CCR Files updated?

    Corresponding with database releases, the CCR Files are updated annually for the SID, NIS, and NRD and every 3 years for the KID.


  • When using multiple years of data, should researchers use the most recent version of the CCR Files or should they match the file to the specific year of data?

    The CCR Files are unique by year. Use the CCR File that corresponds with the year of data.


  • How can I obtain the CCR Files, and how much do they cost?

    The CCR Files are available free of charge through the HCUP Central Distributor. See Are the HCUP supplemental files included with the databases? for more information.
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  • What are the Supplemental Variables for Revisit Analyses?

    The HCUP Supplemental Variables for Revisit Analyses, or revisit variables, are additional variables that were developed by AHRQ. They facilitate analyses to track patients across time and hospital settings exclusively in the SID, SASD, and SEDD while adhering to strict privacy guidelines.

    Each record in an HCUP database represents one discharge abstract from a hospital setting (inpatient, emergency department, or ambulatory surgery visit). Therefore, if an individual visited the hospital three times in a given year, the HCUP databases would include three separate records in the respective HCUP database. The revisit variables allow researchers to uniformly identify sequential visits for an individual within a State across the SID, SASD, and SEDD and to use the available clinical information to determine whether the visits are unrelated, an expected follow-up, complications from a previous treatment, or an unexpected revisit or rehospitalization.


  • Are Supplemental Variables for Revisit Analyses available for HCUP's State databases?

    The HCUP revisit variables are available for the SID, SASD, and SEDD in select States starting in 2003. Appendix A of the HCUP Supplemental Variables for Revisit Analyses User Guide (PDF file, 1.6 MB) provides a detailed list of which States, years, and types of data are available. The revisit variables are designed to be used exclusively with the HCUP State databases and are unique by State and data year.


  • Are the Supplemental Variables for Revisit Analyses available for HCUP's nationwide databases?

    Analyses of readmissions using the HCUP revisit variables are possible only by using the NRD and the HCUP State databases. No other HCUP nationwide database includes the revisit variables.


  • How often are the Supplemental Variables for Revisit Analyses updated?

    The HCUP revisit variables are updated annually.


  • If I am using multiple years of data, should I use the most recent version of the Supplemental Variables for Revisit Analyses or should I match the file to my year of data?

    The revisit variables are unique by State and by year. Use the revisit variables that correspond with the year of data.


  • How do I obtain the Supplemental Variables for Revisit Analyses, and how much do they cost?

    Beginning with 2009 data, the revisit variables are included in the Core file of the SID, SASD, and SEDD databases that are purchased through the HCUP Central Distributor. For 2003-2008 data, the revisit variables are provided free of charge as a separate file with the applicable State databases. If the HCUP State databases were purchased before the release of the revisit variables, then these supplemental files are available free of charge through the HCUP Central Distributor.
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  • What is the Chronic Condition Indicator (CCI)?

    The CCI is a tool developed by the AHRQ that categorizes ICD-9-CM and ICD-10 diagnoses codes into one of two categories: chronic or not chronic. Examples of chronic conditions include malignancies, diabetes, most forms of mental illness, hypertension, many forms of heart disease, and congenital anomalies. Conditions that are not chronic include infections, pregnancy, many neonatal conditions, nonspecific symptoms, and injuries. There are two versions of the CCI: the CCI for ICD-9-CM and the Beta CCI for ICD-10-CM.


    • The ICD-9-CM CCI was updated annually and is valid for codes from January 1, 1980 through September 30, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM implementation and regular maintenance of the codes has been suspended.
    • The Beta ICD-10-CM CCI is updated annually and is valid for codes from October 1, 2015, forward.
      • Caution: These ICD-10-CM/PCS tools were created prior to the availability of ICD-10-CM/PCS-coded data. AHRQ is conducting analyses of ICD-10-CM/PCS data; preliminary findings suggest some unexpected discontinuities between the tools based on ICD-9-CM and those based on ICD-10-CM/PCS. See www.hcup-us.ahrq.gov/datainnovations/icd10_resources.jsp for details. The tools will undergo periodic updates and corrections as data using ICD-10-CM/PCS codes come into greater use. You are advised to visit this page regularly to download and apply the most recent version of the HCUP tools for your data throughout your research process.


  • How often is the CCI updated?

    The Beta CCI for ICD-10-CM is updated each year and is based on ICD-10-CM and Medicare Severity-diagnosis related group (MS-DRG) codes that are valid through September 30 of the designated fiscal year after October 1, 2015.


  • The CCI for ICD-9-CM is based on ICD-9-CM and MS-DRG codes that are valid in the designated fiscal year through September 30, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.

  • How can I obtain the CCI, and how much does it cost?

    The Beta CCI for ICD-10-CM can be downloaded free of charge from the HCUP-US Web site here. To download the CCI for ICD-9-CM, please click here.
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  • What is the Elixhauser Comorbidity Software?

    The Elixhauser Comorbidity Software is a product developed by AHRQ that identifies comorbidities in hospital discharge records using ICD-9-CM or ICD-10-CM diagnosis codes. Currently, the Elixhauser Comorbidity Software creates 29 variables that identify major comorbidities (e.g., Congestive Heart Failure, HIV and AIDS) in hospital discharge records. There are two versions of the Elixhauser Comorbidity Software: the Elixhauser Comorbidity Software for ICD-9-CM and the Beta Elixhauser Comorbidity Software for ICD-10-CM.

    • The Elixhauser Comorbidity Software for ICD-9-CM was updated annually from January 1, 1980 through September 30, 2015. The ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.
    • The Beta Elixhauser Comorbidity Software for ICD-10-CM is updated annually and is valid for codes from October 1, 2015, forward.
      • Caution: These ICD-10-CM/PCS tools were created prior to the availability of ICD-10-coded data. AHRQ is conducting analyses of ICD-10-CM/PCS data; preliminary findings suggest some unexpected discontinuities between the tools based on ICD-9 and those based on ICD-10-CM/PCS. See www.hcup-us.ahrq.gov/datainnovations/icd10_resources.jsp for details. The tools will undergo periodic updates and corrections as data using ICD-10-CM/PCS codes come into greater use. You are advised to visit this page regularly to download and apply the most recent version of the HCUP tools for your data throughout your research process.

  • How does the Elixhauser Comorbidity Software differ from the Elixhauser Comorbidities?

    The Beta Elixhauser Comorbidity Software for ICD-10-CM and the Elixhauser Comorbidity Software for ICD-9-CM are based on the Elixhauser Comorbidities. The most recent versions of the Elixhauser Comorbidity Software contain 29 comorbidity indicators—not the 30 indicators presented in the Elixhauser et al. (1998) article. Beginning with the Fiscal Year 2004 version 2.0 of the Elixhauser Comorbidity Software, Dr. Elixhauser removed the cardiac arrhythmias indicator because of concerns about reliability. In addition, some original labels changed, and some indicators began sharing duplicate ICD-9-CM codes in later versions. Each year, efforts are made to enhance the Elixhauser Comorbidity Software with better methods of identifying the Elixhauser Comorbidities.


  • How often is the Elixhauser Comorbidity Software updated?

    The Beta Elixhauser Comorbidity Software for ICD-10-CM is updated each year, and each version is based on ICD-10-CM and MS-DRG codes that are valid through September 30, 2015 of the designated fiscal year after October 1, 2015.


  • The Elixhauser Comorbidity Software for ICD-9-CM is based on ICD-9-CM and MS-DRG codes that are valid in the designated fiscal year through September 30, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.

  • If I am using multiple years of data, should I use the most recent version of the Elixhauser Comorbidity Software or should I match the software to my year of data?

    To ensure that the codes included in your data sets are included in the Beta Elixhauser Comorbidity Software for ICD-10-CM, or the Elixhauser Comorbidity Software for ICD-9-CM, we recommend that you use the corresponding Elixhauser Comorbidity Software for each year of data.


  • How can I obtain the Elixhauser Comorbidity Software, and how much does it cost?

    The Beta Elixhauser Comorbidity Software for ICD-10-CM can be downloaded free of charge from the HCUP-US Web site here. To download the Elixhauser Comorbidity Software for ICD-9-CM, please click here.
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  • What are the Procedure Classes?

    The Procedure Classes are tools developed by AHRQ that categorize procedure codes into one of four broad categories: Minor Diagnostic, Minor Therapeutic, Major Diagnostic, and Major Therapeutic. Procedure codes for these tools are based on ICD-9-CM and ICD-10-PCS procedure codes (data year dependent). There are two versions of the tool: Procedure Classes for ICD-9-CM and the Beta Procedure Classes for ICD-10-PCS.

    • The Procedure Classes for ICD-9-CM were updated annually from January 1, 1980, through September 30, 2015. The ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.
    • The Beta Procedure Classes for ICD-10-PCS are updated annually and are valid for codes from October 1, 2015 forward.
      • Caution: These ICD-10-CM/PCS tools were created prior to the availability of ICD-10-CM/PCS-coded data. AHRQ is conducting analyses of ICD-10-CM/PCS data; preliminary findings suggest some unexpected discontinuities between the tools based on ICD-9 and those based on ICD-10-CM/PCS. See www.hcup-us.ahrq.gov/datainnovations/icd10_resources.jsp for details. The tools will undergo periodic updates and corrections as data using ICD-10-CM/PCS codes come into greater use. You are advised to visit this page regularly to download and apply the most recent version of the HCUP tools for your data throughout your research process.


  • How often are the Procedure Classes updated?

    The Beta Procedure Classes for ICD-10-PCS are updated annually. Each version is based on ICD-10-CM and MS-DRG codes that are valid through September 30 of the designated fiscal year after October 1, 2015.

    The Procedure Classes for ICD-9-CM are based on ICD-9-CM and MS-DRG codes that are valid in the designated fiscal year through September 30, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.


  • How can I obtain the Procedure Classes, and how much do they cost?

    The Procedure Classes for ICD-9-CM can be downloaded free of charge from the HCUP-US Web site here. To download Beta Procedure Classes for ICD-10-PCS, please click here.
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  • What are the Utilization Flags?

    The Utilization Flags are software developed by AHRQ that creates 30 data elements that reveal additional information about the use of health care services. It combines information from UB-04 revenue codes (data year dependent) and ICD-9-CM or ICD-10-PCS procedure codes, to create indicators (or flags) of utilization. Use of certain departments, procedures, and services such as the Intensive Care Unit (ICU), Coronary Care Unit (CCU), Emergency Department, and specific diagnostic tests and therapies in HCUP's State databases can be assessed with the Utilization Flags. There are two versions of the tool: Utilization Flags for ICD-9-CM and Beta Utilization Flags for ICD-10-PCS.

    • The Utilization Flags for ICD-9-CM were updated beginning in 1993 through Fiscal Year 2014. After September 30, 2015, the ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.
    • The Beta Utilization Flags for ICD-10-PCS are updated annually and are valid for codes from October 1, 2015, forward.
      • Caution: These ICD-10-CM/PCS tools were created prior to the availability of ICD-10-CM/PCS-coded data. AHRQ is conducting analyses of ICD-10-CM/PCS data; preliminary findings suggest some unexpected discontinuities between the tools based on ICD-9-CM and those based on ICD-10-CM/PCS. See www.hcup-us.ahrq.gov/datainnovations/icd10_resources.jsp for details. The tools will undergo periodic updates and corrections as data using ICD-10-CM/PCS codes come into greater use. You are advised to visit this page regularly to download and apply the most recent version of the HCUP tools for your data throughout your research process.

    For additional information, the HCUP Methods Series Report #2006-04: Development of Utilization Flags for Use With UB-92 Administrative Data has detailed documentation about the initial development of the Utilization Flags.


  • Can the Utilization Flags be used on HCUP's nationwide databases?

    No. Beta Utilization Flags for ICD-10-PCS and Utilization Flags for ICD-9-CM can be used only on HCUP's State databases. The Utilization Flags use revenue codes, which are not reported in the nationwide databases. In most HCUP State databases, revenue codes are stored in an array (REVCD1-REVCDn, where n indicates the dimension of the array) with a corresponding array of associated charges. The number of revenue codes reported on an individual record varies; not all participating HCUP Partners provide revenue codes in their State databases. Composition and completeness vary by State, year, and database.


  • How often are the Utilization Flags updated?

    The Beta Utilization Flags for ICD-10-PCS are updated as appropriate following annual review of revenue code categories after October 1, 2015.

    The Utilization Flags for ICD-9-CM are based on ICD-9-CM procedure codes and revenue codes that are valid in the designated fiscal year through September 30, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM/PCS implementation and regular maintenance of the codes has been suspended.


  • How can I obtain the Utilization Flags, and how much do they cost?

    The Beta Utilization Flags for ICD-10-PCS can be downloaded free of charge from the HCUP-US Web site. To download the Utilization Flags for ICD-9-CM, please click here.
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  • What is HCUPnet?

    HCUPnet is a free, online query system that provides statistics and data tables based on HCUP data. Its easy, step-by-step process allows users to explore many health care topics relating to hospital inpatient services, emergency department, and ambulatory settings. Users also may generate tables and graphs on national, regional, and county-level statistics including hospital readmissions and trends on hospital, emergency department, and ambulatory surgery use in the United States. In addition, State-specific statistics are available for States that have agreed to participate in HCUPnet.

    HCUPnet can access statistics from all its hospital databases: the NIS, the KID, the NRD, the NEDS, selected SID, selected SASD, and selected SEDD.


  • Information provided by HCUPnet includes:

    • Primary and secondary diagnoses and procedures
    • Patient demographic characteristics
    • Hospital characteristics
    • Expected payer
    • Total charges
    • Discharge status
    • Length of stay

    Details are provided for conditions, procedures, diagnosis-related groups (MS-DRGs), external cause of injury codes, and major diagnostic categories by patient characteristics (age, sex, payer, community-level income, and urban/rural location), hospital characteristics (ownership, bedsize, teaching status, and rural/urban location), and region of the country. Statistics can be found for all discharges, for operating room procedures only, or for discharges that do not include maternal and newborn discharges.

    Additional information provided by HCUPnet includes the following:

    • In-hospital mortality for diagnoses and procedures
    • Trends in inpatient and outpatient access, charges, and outcomes
    • Utilization by special populations
    • Most common conditions and procedures
    • Variations in medical practice
    • Charges for specific conditions
    • Quality of care and patient safety
    • Differences in outcomes between hospital type
    • National estimates of hospital readmissions
    • National benchmarks for the AHRQ Quality Indicators™
    • Online z-test calculator to test statistical significance of differences between two weighted counts, means, or percentages

  • How is HCUPnet different from the full HCUP databases?

    HCUPnet produces output by accessing precalculated tables and graphs of HCUP data to produce quick statistical results. For this reason, and to protect patient confidentiality, not all types of queries are possible using HCUPnet. The full HCUP databases are purchased through the HCUP Central Distributor and require a statistical software package (such as SAS, SPSS, or Stata) for use. Researchers can program the software to extract the type of information they are seeking from the databases.

    HCUP Partners decide whether to release their State-level, public-release data through the HCUP Central Distributor and whether to have State-level statistics on HCUPnet. As a result, data from any given State may be available through one or both sources, and the years of participation can vary. Please review HCUPnet for a list of participating States and years of participation. For the Central Distributor, a summary table shows State participation by database and year. Complete database availability and pricing information is provided in the Database Catalog, which is found by navigating to the online HCUP Central Distributor.

    Additionally, national statistics are not available for all NIS years on HCUPnet.


  • Is the national data on HCUPnet weighted?

    Yes. Unlike the full HCUP databases that are purchased through the HCUP Central Distributor, HCUPnet statistics have had the weighting applied. The data from HCUPnet are national estimates.


  • How often is HCUPnet updated?

    HCUPnet is updated as databases are released. The national statistics are updated annually, and State statistics are updated as new State data are processed. Available States and years are listed on the HCUPnet pathways.


  • HCUPnet provides national readmission statistics. Is this information available in a full nationwide database?

    Yes. Statistics on national readmission rates are available on HCUPnet or through the NRD. The NRD can be purchased through the HCUP Central Distributor.


  • How does HCUPnet work?

    HCUPnet is based on aggregate statistics tables to speed up data transfer and protect individual records, so not all possible queries can be addressed. HCUPnet is designed to walk the user through each step of building a query.
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  • What articles and reports are available on the HCUP-US Web site?

    HCUP produces a number of publication series featuring HCUP data and tools. These publications and reports provide people with ready-made sources of statistics and guidance on a range of health-care related subjects. Examples include the following:


    Additionally, the HCUP-US Web site has an HCUP Publications Search feature, which allows visitors to search keywords for peer-reviewed articles and AHRQ reports that used HCUP data or products to support their research. The HCUP-US Web site showcases high-quality examples of articles in its Research Spotlights feature.
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  • What types of questions can HCUP User Support answer?

    HCUP User Support can help (1) find, select, and access the appropriate HCUP databases, tools, and documentation; (2) navigate and use the HCUP-US and HCUPnet Web sites; (3) troubleshoot issues with HCUP tools; (4) investigate possible data or documentation errors; (5) support in the interpretation of your HCUP data output; and (6) guide you in the appropriate use and reporting of HCUP data.

    If you have questions concerning current HCUP database orders and invoices, downloading HCUP nationwide databases, unzipping HCUP State or nationwide database products, or submitting required HCUP DUAs, training certificate codes, or data re-use requests, please contact the HCUP Central Distributor.


  • Are there types of questions that HCUP User Support cannot answer?

    HCUP User Support cannot answer questions related to programming software services or support, data coding, complex analyses, research design, or running, revising, or customizing HCUP tools. Staff may be able to guide you to other resources that are specific to your needs.


  • Can HCUP User Support assist with my study design and methodology?

    User Support cannot assist with HCUP research designs. However, many users have found HCUP's Publications Search page helpful in learning how other researchers have constructed their methodology.


  • Are there requirements for publishing with HCUP data?

    Yes. Before publishing with HCUP data, User Support recommends reviewing the Requirements for Publishing With HCUP Data page.
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Internet Citation: HCUP Frequently Asked Questions. Healthcare Cost and Utilization Project (HCUP). November 2018. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/tech_assist/faq.jsp.
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Last modified 11/30/18