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Overview to the HCUP Nationwide Inpatient Sample (NIS), 1999

HEALTHCARE COST AND UTLIZATION PROJECT – HCUP
A FEDERAL-STATE-INDUSTRY PARTNERSHIP IN HEALTH DATA

Sponsored by the Agency for Healthcare Research and Quality

 

 

OVERVIEW TO

THE HCUP NATIONWIDE INPATIENT SAMPLE (NIS),

1999

 

 

These pages provide only an introductory overview to the NIS package.

Full documentation is provided on the NIS Documentation CD-ROM.

 

Issued August 23, 2002

Updated November 2015

 

Agency for Healthcare Research and Quality
Healthcare Cost and Utilization Project (HCUP)

Phone: (866) 290-HCUP (4287)
Internet: hcup@ahrq.gov

NIS Data and Documentation Distributed by:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161

Phone: (866) 290-HCUP (4287)
(703) 605-6000


Table of Contents

Index of Tables


HCUP NATIONWIDE INPATIENT SAMPLE ( NIS)
SUMMARY OF DATA USE LIMITATIONS

***** REMINDER *****


All users of the NIS must take the on–line HCUP Data Use Agreement (DUA) training course, and read and sign a Data Use Agreement.

Authorized users of HCUP data agree to the following restrictions: ‡

  • Will not use the data for any purpose other than research or aggregate statistical reporting.

  • Will not re–release any data to unauthorized users.

  • Will not redistribute HCUP data by posting on any Website or other publically-accessible online repository.

  • Will not identify or attempt to identify any individual, including by the use of vulnerability analysis or penetration testing. Methods that could be used to identify individuals directly or indirectly shall not be disclosed or published.

  • Will not publish information that could identify individual establishments (e.g., hospitals) ) and will not contact establishments.

  • Will not use the data concerning individual establishments for commercial or competitive purposes involving those establishments and will not use the data to determine rights, benefits, or privileges of individual establishments.

  • Will not use data elements from the proprietary severity adjustment software packages (3M APR–DRGs, HSS APS–DRGs, and Truven Health Analytics Disease Staging) for any commercial purpose or to disassemble, decompile, or otherwise reverse engineer the proprietary software.

  • Will acknowledge in reports that data from the "Healthcare Cost and Utilization Project (HCUP)", were used, including names of the specific databases used for analysis.

  • Will acknowledge that risk of individual identification of persons is increased when observations (i.e., individual discharge records) in any given cell of tabulated data is less than or equal to 10.

Any violation of the limitations in the Data Use Agreement is punishable under Federal law by a fine of up to $10,000 and up to 5 years in prison. Violations may also be subject to penalties under State statutes.

† The on–line Data Use Agreement training session and the Data Use Agreement are available on the HCUP User Support (HCUP–US) Website at http://www.hcup-us.ahrq.gov.
‡ Specific provisions are detailed in the Data Use Agreement for Nationwide Databases.


HCUP CONTACT INFORMATION

All HCUP data users, including data purchasers and collaborators, must complete the online HCUP Data Use Agreement (DUA) Training Tool, and read and sign the HCUP Data Use Agreement. Proof of training completion and signed Data Use Agreements must be submitted to the HCUP Central Distributor as described below.

The on-line DUA training course is available at: http://www.hcup-us.ahrq.gov/tech_assist/dua.jsp.

The HCUP Nationwide Data Use Agreement are is available on the AHRQ-sponsored HCUP User Support (HCUP-US) Web site at:

http://www.hcup-us.ahrq.gov


HCUP Central Distributor

Data purchasers will be required to provide their DUA training completion code and will execute their DUAs electronically as a part of the online ordering process. The DUAs and training certificates for collaborators and others with access to HCUP data should be submitted directly to the HCUP Central Distributor using the contact information below.

The HCUP Central Distributor can also help with questions concerning HCUP database purchases, your current order, training certificate codes, or invoices, if your questions are not covered in the Purchasing FAQs on the HCUP Central Distributor Web site.

HCUP User Support:

Information about the content of the HCUP databases is available on the HCUP User Support (HCUP-US) Web site (http://www.hcup-us.ahrq.gov). If you have questions about using the HCUP databases, software tools, supplemental files, and other HCUP products, please review the HCUP Frequently Asked Questions or contact HCUP User Support:


HEALTHCARE COST AND UTILIZATION PROJECT – HCUP
A FEDERAL-STATE-INDUSTRY PARTNERSHIP IN HEALTH DATA

Sponsored by the Agency for Healthcare Research and Quality


The Agency for Healthcare Research and Quality and
the staff of the Healthcare Cost and Utilization Project (HCUP)
thank you for purchasing the HCUP Nationwide Inpatient Sample ( NIS).



HCUP Nationwide Inpatient Sample ( NIS)

ABSTRACT

The Nationwide Inpatient Sample (NIS) is part of the Healthcare Cost and Utilization Project (HCUP), sponsored by the Agency for Healthcare Research and Quality (AHRQ), formerly the Agency for Health Care Policy and Research.

The NIS is a database of hospital inpatient stays. Researchers and policymakers use the NIS to identify, track, and analyze national trends in health care utilization, access, charges, quality, and outcomes.

The NIS is the largest all-payer inpatient care database that is publicly available in the United States, containing data from approximately 7 million hospital stays. The 1999 NIS contains all discharge data from about 1,000 hospitals located in 24 States, approximating a 20-percent stratified sample of U.S. community hospitals. The NIS is available for a 12-year time period, from 1988 to 1999, allowing analysis of trends over time.

The NIS is the only national hospital database with charge information on all patients, regardless of payer, including persons covered by Medicare, Medicaid, private insurance, and the uninsured. The NIS's large sample size enables analyses of rare conditions, such as congenital anomalies; uncommon treatments, such as organ transplantation; and special patient populations, such as children.

Inpatient stay records in the NIS include clinical and resource use information typically available from discharge abstracts. Hospital and discharge weights are provided for producing national estimates. The NIS can be linked to hospital-level data from the American Hospital Association's Annual Survey of Hospitals and county-level data from the Bureau of Health Professions' Area Resource File, except in those states that do not allow the release of hospital identifiers.

Beginning in 1998, the NIS differs from previous NIS releases: some data elements were dropped, some were added, for some data elements the coding was changed, and the sampling and weighting strategy was revised to improve the representativeness of the data.

Access to the NIS is open to users who sign data use agreements. Uses are limited to research and aggregate statistical reporting.

INTRODUCTION TO THE HCUP NATIONWIDE INPATIENT SAMPLE ( NIS )

OVERVIEW OF NIS DATA

The Nationwide Inpatient Sample contains all-payer data on hospital inpatient stays from States participating in the Healthcare Cost and Utilization Project (HCUP). Each year of the NIS provides information on approximately 5 million to 7 million inpatient stays from about 1,000 hospitals. All discharges from sampled hospitals are included in the NIS database.

The NIS contains patient-level clinical and resource use information included in a typical discharge abstract. The NIS can be linked directly to hospital-level data from the American Hospital Association (AHA) Annual Survey of Hospitals and to county-level data from the Health Resources and Services Administration Bureau of Health Professions’ Area Resource File (ARF), except in those states that do not allow the release of hospital identifiers.

The NIS is designed to approximate a 20-percent sample of U.S. community hospitals, defined by the AHA to be "all nonfederal, short-term, general, and other specialty hospitals, excluding hospital units of institutions." Included among community hospitals are specialty hospitals such as obstetrics-gynecology, ear-nose-throat, short-term rehabilitation, orthopedic, and pediatric institutions. Also included are public hospitals and academic medical centers. Excluded are short-term rehabilitation hospitals (beginning with 1998 data) long-term hospitals, psychiatric hospitals, and alcoholism/chemical dependency treatment facilities.

This universe of U.S. community hospitals is divided into strata using five hospitals characteristics: ownership/control, bed size, teaching status, urban/rural location, and U.S. region.

The NIS is a stratified probability sample of hospitals in the frame, with sampling probabilities proportional to the number of U.S. community hospitals in each stratum. The frame is limited by the availability of inpatient data from the data sources.

In order to improve the representativeness of the NIS, the sampling and weighting strategy was modified beginning with the 1998 data. The full descriptions of this process can be found in the special report on Changes in NIS Sampling and Weighting Strategy for 1998 which will be available from AHRQ in late 2001. To facilitate the production of national estimates, both hospital and discharge weights are provided, along with information necessary to calculate the variance of estimates. Detailed information on the design of the NIS is available in the year-specific special reports on Design of the Nationwide Inpatient Sample found on the NIS Documentation CD-ROM.

NIS data sets are currently available for multiple years, as shown in Table 1. Each release of the NIS includes:

Table 1. Summary of NIS Releases
 Data from   Media/format options   Structure of Releases
  • 1988-1992
  • 8 States in 1988
  • 11 States in 1989-1992
  On CD-ROM,
in ASCII format




On magnetic tape,
in EDCDIC or SAS
transport format
5 years of NIS data in a 26-CD set
4 CDs per year (one quarter per disk)
Two 10% Subsamples of discharges for each year


Each year sold separately
  • 1993
  • 17 states
  • 1994
  • 17 states
  • 1995
  • 19 states
  • 1996
  • 19 states
  • 1997
  • 22 states
bracket spanning the years 1993-2000 for the media format: ON CD-Rom, in ASCII format On CD-ROM,
in ASCII format
1 year of data in a 6-CD set,
structured for use on microcomputers

Two 10% subsamples of discharges for each year
  • 1998
  • 22 states
  • 1999
  • 24 states
bracket spanning the years 1993-2000 for the media format: ON CD-Rom, in ASCII format On CD-ROM,
in ASCII format
1 year of data in a 2-CD set,
compressed files

Two 10% subsamples of discharges for each year

NIS Data Sources, Hospitals, and Inpatient Stays

Table 2 summarizes the data sources, number of hospitals, and number of inpatient stays in NIS data.

Table 2. Summary of NIS Data Sources, Hospitals and Inpatient Stays, 1988-2000
Calendar Year Data sources Number of hospitals Number of inpatient stays
1988 CA CO FL IL IA MA NJ WA 759 5,265,756
1989 AZ CA CO FL IL IA MA NJ PA WA WI
(Added AZ, PA, WI)
882 6,110,064
1990 AZ CA CO FL IL IA MA NJ PA WA WI
(No change)
871 6,268,515
1991 AZ CA CO FL IL IA MA NJ PA WA WI
(No change)
859 6,156,188
1992 AZ CA CO FL IL IA MA NJ PA WA WI
(No change)
856 6,195,744
1993 AZ CA CO CT FL IL IA KS MD MA
NJ NY OR PA SC WA WI
(Added CT, KS, MD, NY, OR, SC)
913 6,538,976
1994 AZ CA CO CT FL IL IA KS MD MA
NJ NY OR PA SC WA WI
(No change)
904 6,385,011
1995 AZ CA CO CT FL IL IA KS MD MA
MO NJ NY OR PA SC TN WA WI
(Added MO, TN)
938 6,714,935
1996 AZ CA CO CT FL IL IA KS MD MA
MO NJ NY OR PA SC TN WA WI
(No change)
906 6,542,069
1997 AZ CA CO CT FL GA HI IL IA KS MD MA
MO NJ NY OR PA SC TN UT WA WI
(Added GA, HI, UT)
1,012 7,148,420
1998 AZ CA CO CT FL GA HI IL IA KS MD MA
MO NJ NY OR PA SC TN UT WA WI
(No change)
984 6,827,350
1999 AZ CA CO CT FL GA HI IL IA KS MD MA ME MO NJ NY OR PA SC TN UT VA WA WI
(Added ME, VA)
984 7,198,929

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State-Specific Restrictions

Some data sources that contributed data to the NIS imposed restrictions on the release of certain data elements or on the number and types of hospitals that could be included in the database. Detailed information on these state-specific restrictions is available in the special report on Sources of NIS Data and State-specific Restrictions on the NIS Documentation CD-ROM.

Contents of CD-ROM Set

There are two types of files included in the NIS: 1) data files and 2) documentation and tools files.

  1. Data Files - three types of ASCII formatted data files are included in the NIS:

    Inpatient Core File: This inpatient discharge-level file contains data for 100% of the discharges from a sample of hospitals in participating states.

    Subsample Inpatient Core Files: Each of these discharge-level files contain all data elements from the Core File, for a 10% subsample of discharges from the NIS; these can be combined to create a 20% NIS subsample. These files can be useful for testing programs or validating models.

    Hospital Weights File: This hospital-level file contains one observation for each hospital included in the NIS and contains weights and variance estimation data elements, as well as linkage data elements. The unit of observation is the hospital. The HCUP hospital identifier (HOSPID) provides the linkage between the NIS Inpatient Core files and the Hospital Weights file.
  2. Documentation and Tools Files

    Documentation: Complete file documentation, variable notes, and summary statistics are provided in a series of Portable Document Format (*.pdf) files. These files are detailed in Table 6.

    SAS source code: Code is included for the format library for the variables and for loading ASCII data into SAS format.

    SPSS source code:
    Code is included for the variable library and for loading ASCII data into SPSS format.

    Labels: Labels for the Clinical Classifications Software (CCS), formerly called the Clinical Classifications for Health Policy Research (CCHPR), and for the Diagnosis-Related Groups (multiple versions).

    File Specifications: Record layouts for all data files.

NIS Data Elements

All releases of the NIS contain two types of data: inpatient stay records and hospital information with weights. Table 3 and Table 4 identify the data elements that can be found in the inpatient stay and hospital weights files, respectively. This is not complete documentation for the data; please refer to the NIS Documentation CD-ROM for full documentation on all data elements and for the record layout.

Table 3. Data Elements in the NIS Inpatient Core Files, Starting in 1999

Note: Beginning in 1998, the NIS differs from previous NIS releases; some data elements were dropped, some added, and for some data elements the values were changed.

Data Element Description (numbers in brackets indicate variable coding)
AGE Age in years at admission
AGEDAY Age in days (coded only when the age in years is less than 1) at admission
AMONTH Admission month
ASOURCE Admission source: (1) ER, (2) another hospital, (3) another facility including long-term care, (4) court/law enforcement, (5) routine/birth/other
ASOURCE_X Admission source, as received from data source.*
ATYPE Admission type: (1) emergency, (2) urgent, (3) elective, (4) newborn, (6) other
AWEEKEND Admission on weekend: (0) admission on Monday-Friday, (1) admission on Saturday-Sunday
DIED Indicates in-hospital death: (0) did not die during hospitalization, (1) died during hospitalization
DISCWT Discharge weight (on Core file and Hospital Weights file)
DISCWT10 Discharge weight (on 10% subsample file)
DISPUB92 Disposition of patient (discharge status), UB92 coding: (1) routine, (2) short term hospital, (3) skilled nursing facility, (4) intermediate care, (5) another type of facility, (6) home health care, (7) against medical advice, (8) home IV provider, (20) died in hospital, (40) died at home, (41) died in a medical facility, (42) died, place unknown, (50) Hospice, home, (51) Hospice, medical facility
DISPUniform Disposition of patient (discharge status), uniform coding: (1) routine, (2) transfer to short term hospital, (3) other transfers, including skilled nursing facility, intermediate care, and another type of facility, (6) home health care, (7) against medical advice, (20) died in hospital
DQTR Discharge quarter
DRG Diagnosis Related Group (DRG) in use on discharge date
DRG10 DRG Version 10 (effective October 1992 - September 1993).
DRG18 DRG Version 18 (effective October 2000 - September 2001).
DRGVER Grouper version in use on discharge date
DSHOSPID Hospital number as received from the data source
DX1-DX15 Principal and secondary diagnoses
DXCCS1-DXCCS15 Clinical Classifications Software (CCS) category for all diagnoses
FEMALE Gender of patient: (0) male, (1) female
HOSPID HCUP hospital number (links to Hospital Weights file)
HOSPST State postal code for hospital (e.g., AZ for Arizona)
HOSPSTCO Modified Federal Information Processing Standards (FIPS) State/county code for hospital, links to Area Resource File (available from the Bureau of Health Professions, Health Resources and Services Administration)
KEY Unique record number
LOS Length of stay, edited
LOS_X Length of stay, as received from data source
MDC Major Diagnosis Category (MDC) in use on discharge date
MDC10 MDC Version 10 (effective October 1992 - September 1993).
MDC18 MDC Version 18 (effective October 2000 - September 2001).
MDID_S Synthetic attending physician number.
NDX Number of diagnoses coded on the original record
NEOMAT Neonatal/maternal flag: (0) not maternal or neonatal, (1) maternal diagnosis or procedure, (2) neonatal diagnosis, (3) maternal and neonatal on same record
NPR Number of procedures coded on the original record
PAY1 Expected primary payer, uniform: (1) Medicare, (2) Medicaid, (3) private including HMO, (4) self-pay, (5) no charge, (6) other
PAY1_X Expected primary payer, as received from the data source.*
PAY2 Expected secondary payer, uniform: (1) Medicare, (2) Medicaid, (3) private including HMO, (4) self-pay, (5) no charge, (6) other
PAY2_X Expected secondary payer, as received from the data source*
PR1-PR15 Principal and secondary procedures
PRCCS1-PRCCS15 Clinical Classifications Software (CCS) for all procedures
PRDAY1-PRDAY15 For each procedure, the number of days from admission
RACE Race includes (1) white, (2) black, (3) Hispanic, (4) Asian or Pacific Islander, (5) Native American, (6) other
SURGID_S Synthetic primary physician number
TOTCHG Total charges, edited
TOTCHG_X Total charges, as received from data source
YEAR Calendar year
ZIPINC Median income for patient's ZIP Code: (1) $1-$24,999, (2) $25,000-$34,999, (3) $35,000-$44,999, (4) $45,000 and above
*For categorical data elements with _X suffix, see Description of Data Elements (on the NIS Documentation CD-ROM) for state-specific coding.

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Table 4. Data Elements in the NIS Hospital Weights File, Starting in 1999

Note: Beginning in 1998, the NIS differs from previous NIS releases; some data elements were dropped, some added, and for some data elements the values were changed.

Data Element Description (numbers in brackets indicate variable coding)
AHAID AHA hospital identifier that matches AHA Annual Survey of Hospitals (not available for all states)
DISCWT Weight to discharges in AHA universe
HOSPADDR Hospital address from AHA Survey (not available for all states)
HOSPCITY Hospital city from AHA Survey (not available for all states)
HOSPID HCUP hospital number (links to inpatient Core files)
HOSPNAME Hospital name from AHA Survey (not available for all states)
HOSPST state postal code for hospital (e.g., AZ for Arizona)
HOSPWT Weight to hospitals in AHA universe
HOSPZIP Hospital zip code from AHA Survey (not available for all states)
HOSP_BEDSIZE Bed size of hospital: (1) small, (2) medium, (3) large
HOSP_CONTROL Control/ownership of hospital: (0) government or private, collapsed category, (1) government, nonfederal, public, (2) private, non-profit, voluntary, (3) private, invest-own, (4) private, collapsed category
HOSP_LOCATION Location: (0) rural, (1) urban
HOSP_LOCTEACH Location/teaching status of hospital: (1) rural, (2) urban non-teaching, (3) urban teaching
HOSP_REGION Region of hospital: (1) Northeast, (2) Midwest, (3) South, (4) West
HOSP_TEACH Teaching status of hospital: (0) non-teaching, (1) teaching
IDNUMBER AHA hospital identifier without the leading 6 (not available for all states)
NIS_STRATUM Stratum used to sample hospitals; includes geographic region, control, location/teaching status, and bed size
N_DISC_U Number of AHA universe discharges in NIS_STRATUM
N_HOSP_U Number of AHA universe hospitals in NIS_STRATUM
S_DISC_U Number of sample discharges in NIS_STRATUM
S_HOSP_U Number of sample hospitals in NIS_STRATUM
TOTAL_DISC Total number of discharges from this hospital in the NIS
YEAR Calendar year

SAMPLING OF HOSPITALS INCLUDED IN THE NIS

The hospital universe is defined by all hospitals that were open during any part of each calendar year and were designated as community hospitals in the AHA Annual Survey of Hospitals.

For more information on how hospitals in the data were mapped to hospitals as defined by the AHA, refer to the special report: HCUP Hospital Identifiers. For a list of all data sources, refer to: Sources of NIS Data and State-Specific Restrictions. For more detailed descriptions of the sampling design, refer to the year-specific special reports Design of the HCUP Nationwide Inpatient Sample. All reports can be found on the NIS Documentation CD-ROM.

Stratification Variables

To help ensure generalizability, five hospital sampling strata were defined based on hospital characteristics contained in the AHA Annual Survey of Hospitals. The stratification variables are:

Rural hospitals were not split according to teaching status, because rural teaching hospitals were rare.

To further ensure geographic representativeness, implicit stratification variables included state and three-digit zip code (the first three digits of the hospital’s five digit zip code). The hospitals were sorted according to these variables prior to systematic random sampling.

Table 5. Bed Size Categories, by Region
Location and Teaching Status Hospital Bed size
Small Medium Large
NORTHEAST
Rural 1-49 50-99 100+
Urban,non-teaching 1-124 125-199 200+
Urban, teaching 1-249 250-424 425+
MIDWEST
Rural 1-29 30-49 50+
Urban,non-teaching 1-74 75-174 175+
Urban, teaching 1-249 250-374 375+
SOUTH
Rural 1-39 40-74 75+
Urban, non-teaching 1-99 100-199 200+
Urban, teaching 1-249 250-449 450+
WEST
Rural 1-24 25-44 45+
Urban, non-teaching 1-99 100-174 175+
Urban, teaching 1-199 200-324 325+

GETTING STARTED

NIS information is provided on two CD-ROMs. The NIS data files are on CD-ROM #1 and the NIS documentation and tools are on CD-ROM #2.

NIS Data Files

In order to load NIS data onto your PC, you will need 4 gigabytes of space available. Because of the size of the files, the data are distributed as self-extracting PKZIP compressed files. To decompress the data, you should follow these steps:

  1. Create a directory for the NIS on your hard drive.
  2. Copy the self-extracting data files from the NIS Data Files CD-ROM into the new directory.
  3. Unzip each file by running the corresponding *.exe file.
    • Type the file name within DOS or click on the name within Windows Explorer.
    • Edit the name of the "Unzip To Folder" in the WinZip Self Extractor dialog to select the desired destination directory for the extracted file.
    • Click on the "Unzip" button.

The ASCII data files will then be uncompressed into this directory. After the files are uncompressed, the *.exe files can be deleted.

NIS Documentation

NIS documentation files on the Documentation CD-ROM provide important resources for the user. Refer to these resources to understand the structure and content of the NIS and to aid in using the NIS. Many of the documentation files are provided in portable document format (*.pdf) files. Files with the *.pdf extension can be viewed, searched, and printed using the Adobe™ Acrobat™ Reader.

You must have the Adobe™ Acrobat™ Reader software on your computer to access the NIS documentation. If you do not have Adobe™ Acrobat™ Reader software on your computer, see the DOCUMENTATION.README.TXT file on NIS Documentation CD-ROM for instructions on installing or obtaining the software.

The Acrobat™ Reader provided on the NIS Documentation CD-ROM is for IBM-compatible microcomputers running Microsoft Windows 95 or higher. More information and Acrobat™ Reader software for other platforms (DOS, Windows 3.1, Macintosh, Sun Systems, etc.) may be obtained free of charge from the Adobe Home Page at http://www.adobe.com/. Exit Disclaimer For further assistance in installing and running the Adobe™ Acrobat™ Reader on your computer platform, please consult your local support personnel.

Table 6 describes the documentation and tools files that can be found on the NIS Documentation CD-ROM and illustrates the structure of the directories and subdirectories on the CD.

Table 6. NIS Documentation CD-ROM
Directory Description
Root Includes:
  • DOCUMENTATION.README.TXT file with information with introductory information on accessing the NIS documentation
/General Information Includes:
  • Overview of the NIS (PDF file)
  • Sources of NIS Data and State-Specific Restrictions (PDF file)
  • Data Use Agreement for the Nationwide Inpatient Sample (PDF file)
/Special Reports Includes:
  • Design of the Nationwide Inpatient Sample (PDF file)
  • Calculating Variances using Data from the HCUP Nationwide Inpatient Sample (PDF file)
  • HCUP Coding Practices (PDF file)
  • HCUP Quality Control Procedures (PDF file)
  • HCUP Hospital Identifiers (PDF file)
/File Specifications Includes data set name, number of records, record length, and record layout. One file per data file: Core, Core Subsample #1, Core Subsample #2, and Hospital Weights. (Text files)
/Description of Data Elements Includes information on all NIS variables such as uniform coding and state-specific information. One file per data type: Core and Hospital Weights. (PDF files)
/Summary Statistics Includes summary statistics (means and frequencies) on NIS data. One file per data file: Core, Core Subsample #1, Core Subsample #2, and Hospital Weights. (PDF files)
/SAS Load Programs SAS programming code to convert ASCII data files into SAS. One file per data file: Core, Core Subsample #1, Core Subsample #2, and Hospital Weights. (Text files)
/SPSS Load Programs SPSS programming code to convert ASCII data files into SPSS. One file per data file: Core, Core Subsample #1, Core Subsample #2, and Hospital Weights. (Text files)
/HCUP Tools_Labels Includes:
  • Label file for the Clinical Classifications Software (CCSs), a categorization scheme that groups ICD-9-CM diagnosis and procedure codes into mutually exclusive categories. (Text file)
  • Label file for Diagnosis Related Groups (DRGs), multiple versions provided (Text file)
  • SAS code to create format library of variable labels (Text file)
/Adobe Acrobat Reader Adobe Acrobat Reader files for IBM compatible for Microsoft Windows 95 or higher. (One text, one HTML, and one application file)

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OTHER HCUP PRODUCTS

The AHRQ Home Page on the World Wide Web is a source of information about HCUP databases and aggregate statistics from HCUP.

The address is: https://www.ahrq.gov/research/data/hcup/index.html.

Data

Nationwide Inpatient Sample (NIS) releases are available from the National Technical Information Service (NTIS); call NTIS for prices at 800-553-6847 or 703-605-6000. An online ordering option is available at http://www.ntis.gov/fcpc. All NIS releases are available on CD-ROM; NIS Release 1 may also be purchased on magnetic tape. Order by PB number.

State Inpatient Databases (SID) are hospital databases from data organizations participating in HCUP. The SID contain the universe of the inpatient discharge abstracts in the participating HCUP States, translated into a uniform format to facilitate multi-State comparisons and analyses. Together, the SID encompass about 60 percent of all U.S. community hospital discharges. For more information, visit: http://www.hcup-us.ahrq.gov/sidoverview.jsp or call the HCUP Central Distributor (see below).

State Ambulatory Surgery Databases (SASD) are databases from data organizations in participating HCUP States, that capture surgeries performed on the same day in which patients are admitted and released. The SASD contain the ambulatory surgery encounter abstracts in participating States, translated into a uniform format to facilitate multi-State comparisons and analyses. All of the databases include abstracts from hospital-affiliated ambulatory surgery sites. Some contain the universe of ambulatory surgery encounter abstracts for that State, including records from both hospital-affiliated and freestanding surgery centers. Composition and completeness of data files may vary from State to State. For more information, visit: http://www.hcup-us.ahrq.gov/sasdoverview.jsp or call the HCUP Central Distributor (see below).

Kids' Inpatient Database (KID)) is a unique database of hospital inpatient stays for children 18 years of age and younger. The KID was specifically designed to permit researchers to study a broad range of conditions and procedures related to child health issues. KID files for 1997 data are available through the AHRQ-sponsored HCUP Central Distributor (contact information below). For more information, visit: http://www.hcup-us.ahrq.gov/kidoverview.jsp or call the HCUP Central Distributor (see below).

HCUP Central Distributor. Many of the HCUP State Partners allow the public release of the State Inpatient Databases (SID) and State Ambulatory Surgery Databases (SASD) through the AHRQ-sponsored HCUP Central Distributor. In addition, the KID is released through the Central Distributor. Information on how to obtain uniformly-formatted HCUP files from States not participating in the HCUP Central Distributor is also available from the HCUP Central Distributor:

HCUPnet

HCUPnet is a Web-based query tool for identifying, tracking, analyzing, and comparing statistics on hospitals at the national, regional, and state level. With HCUPnet you have easy access to national statistics and trends and selected state statistics about hospital stays. HCUPnet guides you step by step to obtain the statistics you need. HCUPnet generates statistics using the Nationwide Inpatient Sample (NIS), the Kids' Inpatient Database (KID), and the State Inpatient Databases (SID) for those states that have agreed to participate. HCUPnet can be found at: http://hcupnet.ahrq.gov/.

TOOLS

AHRQ Quality Indicators (QIs) are clinical performance measures for use with readily available inpatient data. Methods and software for the AHRQ Quality Indicators can be downloaded from http://www.qualityindicators.ahrq.gov/.

Clinical Classifications Software (CCS)), formerly known as the Clinical Classifications for Health Policy Research (CCHPRs), are classification systems that group ICD-9-CM diagnoses and procedures into a limited number of clinically meaningful categories. Methods and software can be downloaded from http://www.hcup-us.ahrq.gov/toolssoftware/ccs/ccs.jsp.

Comorbidity Software assigns variables that identify comorbidities in hospital discharge records using ICD 9 CM diagnosis codes (International Classification of Diseases, Ninth Revision, Clinical Modification). Methods and software can be downloaded from http://www.hcup-us.ahrq.gov/toolssoftware/comorbidity/comorbidity.jsp.

PUBLICATIONS

HCUP Research Notes report aggregate statistics and detailed analyses using HCUP data. To request copies, contact the AHRQ Publications Clearinghouse at (800) 358 9295 or send a postcard to: AHRQ Publications Clearinghouse, P.O. Box 8547, Silver Spring, MD 20907 or visit the AHRQ Home Page.

For information on HCUP products:
Email: hcup@ahrq.gov
Phone: (301) 594-3075
Fax: (301) 594-2166

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DATA USE AGREEMENT FOR THE NATIONWIDE INPATIENT SAMPLE

This agreement must be signed by anyone seeking to use data in the Nationwide Inpatient Sample (NIS) maintained by the Center for Organization and Delivery Studies(CODS), Agency for Healthcare Research and Quality (AHRQ) before access to such data can be granted. All data maintained by CODS/ AHRQ is confidential or proprietary except data specified for restricted access public release, or data authorized by AHRQ and the original data source for re-release.

Under section 924(c) of the Public Health Service Act (42 U.S.C. 299c-3(c)), data that identifies individuals or establishments collected by the Agency for Healthcare Research and Quality (AHRQ) may be used only for the purpose for which they were collected. Data supplied to AHRQ under the auspices of HCUP were provided by the data sources only for research, analysis, and aggregate statistical reporting.

No identification of persons--Any effort to determine the identity of any person contained in the databases (including but not limited to patients, physicians, and other health care providers) or to use the information for any purpose other than for research, analysis, and aggregate statistical reporting would violate the conditions of this data use agreement and therefore the above-referenced AHRQ confidentiality statute. Furthermore, under the statute, no identifying information may be published or released in any way without the consent of the person who supplied the information or who can be identified by the information. AHRQ omits from the data set all direct personal identifiers, as well as characteristics that might lead to identification of persons. It may be possible in rare instances, through complex analysis and with outside information, to ascertain from the data sets the identity of particular persons. Considerable harm could ensue if this were done. By virtue of this agreement, the undersigned agrees that such attempts will be prohibited and that information which could identify individuals directly or by inference will not be released or published. Because of these restrictions, users of the data must agree that they will not attempt to contact individuals for the purpose of verifying information supplied in the HCUP databases. Any questions about the data must be referred to AHRQ only.

Use of Establishment identifiers--Section 924(c) of the Public Health Service Act (42 U.S.C. 299c-3(c) ) also restricts the use of any information that allows the identification of establishments to the purpose for which the information was collected. Permission was obtained from the data sources (state data organizations, hospital associations, and data consortia) to use the identification of hospitals (when such identification appears in the data sets) for the purpose of conducting research only. Such research purpose includes linking institutional information from outside data sets for analysis and aggregate statistical reporting. Such purpose does not include the use of information in the data sets concerning individual establishments for commercial or competitive purposes involving those individual establishments, or to determine the rights, benefits, or privileges of establishments. Users of the data must not identify establishments directly or by inference in disseminated material. In addition, users of the data must not contact establishments for the purpose of verifying information supplied in the HCUP databases. Any questions about the data must be referred to AHRQ only.

The undersigned gives the following assurances with respect to the AHRQ data sets.

I understand that these assurances are collected for the United States Agency for Healthcare Research and Quality to require compliance with its statutory confidentiality requirement. My signature indicates my agreement to comply with the above-stated requirements with the knowledge that any violation of this statute is subject to a civil penalty of up to $10,000 under 42 U.S.C. 299c-3(d), and that deliberately making a false statement about this or any matter within the jurisdiction of any department or agency of the Federal Government violates 18 U.S.C. 1001 and is punishable by a fine of up to $10,000 or up to five years in prison. Violators of this agreement may also be subject to penalties under state confidentiality statutes that apply to these data for particular states.

 
Signed:___________________________________________________________ Date:_________________________
Print or Type Name:_______________________________________________________________________
Title:__________________________________________________________________________________________________
Organization:____________________________________________________________________________________________
Address:________________________________________________________________________________________________
City:______________________________________________________ State:__________ ZIP Code:____________________
Phone Number:______________________________________________ Fax: ________________________________________
E-mail:________________________________________________________________________________________________

Note to Purchaser: Shipment of the data product will only be made to the person who signs this data use agreement.

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Internet Citation: 1999 NIS Introduction. Healthcare Cost and Utilization Project (HCUP). July 2016. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/nation/nis/NIS_Introduction_1999.jsp.
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Last modified 7/28/16