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1993-2002 Nationwide Inpatient Sample (NIS) Supplemental Discharge-Level Files
The 1993-2002 Supplemental Discharge-Level Files provide the NIS data user with both the trend weights and data elements that are consistently defined across data years. These files are created by AHRQ through a Federal-State-Industry partnership.
 
1993-2002 Nationwide Inpatient Sample (NIS) Supplemental Discharge-Level Files

The 1993-2002 NIS Supplemental Discharge-Level Files are discharge-level files that provide the NIS data user with both the trend weights and data elements that are consistently defined across data years. They are part of a family of databases and software tools developed as part of the Healthcare Cost and Utilization Project (HCUP), a Federal-State-Industry partnership sponsored by the Agency for Healthcare Research and Quality. HCUP databases, tools, and software inform decision making at the national, State, and community levels.

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The NIS is available yearly, beginning with 1988, allowing analysis of trends over time. Analyses of time trends using the HCUP NIS are recommended from 1993 forward.

The HCUP National Inpatient Sample (NIS) was redesigned in 1998 and again in 2012 data to improve national estimates. In order to facilitate analysis of trends using multiple years of NIS data, AHRQ developed new discharge trend weights for the 1993-2011 NIS. These weights adjust for changes in the 2012 NIS design and are designed to be used instead of the original NIS discharge weights for trends analysis. For trends analysis spanning 2012 and earlier NIS data, trend weights should be used prior to 2012 data to make estimates comparable to the new 2012 NIS design. The trend weights were developed for trends analysis, but they can be used for all analyses, as is done on the HCUPnet Web site.

The new 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 Nationwide Inpatient Sample to Estimate Trends, available on the HCUP-US Web site under Methods Series, includes recommendations for trends analysis.

The purpose of the 1993-2002 NIS Supplemental Discharge Level-Files is to ease the burden on researchers conducting analyses that span multiple years. These files provide the data user with both the updated trend weights and additional data elements not contained on the original 1993-2002 NIS files, which were added for later years of the NIS through 2002. The following table enumerates the differences in weighted discharges:
YEAR Number of Discharges in the NIS, Weighted Number of Discharges in the NIS, Weighted with Trend Weight Difference HCUPnet Weighted Discharges Difference Comment
1993 34,715,985 33,736,753 -979,232 33,735,002 1,751 HCUPnet removed outlier records.
1994 34,622,203 33,149,768 -1,472,435 33,148,180 1,588 HCUPnet removed outlier records.
1995 34,791,998 33,647,121 -1,144,877 33,644,908 2,213 HCUPnet removed outlier records.
1996 34,874,386 33,386,097 -1,488,289 33,384,374 1,723 HCUPnet removed outlier records.
1997 35,408,207 33,232,257 -2,175,950 33,230,554 1,703 HCUPnet removed outlier records.
1998 34,874,001 33,923,632 -950,369 33,923,632 0  
1999 35,467,673 34,440,994 -1,026,679 34,440,994 0  
2000 36,417,565 35,300,425 -1,117,140 35,300,425 0  
2001 37,187,641 36,093,550 -1,094,091 36,093,550 0  
2002 37,804,021 36,523,831 -1,280,190 36,523,831 0  
 
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The NIS Supplemental Discharge-Level files are designed to be merged with the NIS Core files to produce a dataset containing the complete set of variables from both sources. The DVD contains the Discharge-Level data files, documentation, load programs for SAS, SPSS, and Stata, and an example SAS program to merge the NIS Supplemental Discharge-Level Files with the NIS Core Files. The DVD does not include the NIS Core files, which must be obtained separately from the HCUP Central Distributor.
 
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There is one NIS Supplemental Discharge-Level data file for each year from 1993 to 2002. No supplemental files were created for later years because 2003 served as the base comparison. The 1993-2002 NIS Supplemental Discharge-Level Files are appropriate for use in conjunction with the NIS data files that are available for purchase through the HCUP Central Distributor.
 
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The NIS Supplemental Discharge-Level Files are provided in fixed-width ASCII files. The files require a statistical software package such as SAS, SPSS, or Stata to use for analytic purposes. Load programs for SAS, SPSS, and Stata are provided.
 
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The User Guide for the NIS Supplemental Discharge-Level Files contains:
  • A more detailed description of the files
  • Information on data elements
  • Instructions for SAS and non-SAS users.
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HCUP 1993-2002 NIS Supplemental Discharge-Level Files are available from the HCUP Central Distributor. These files are free of charge. Contact the HCUP Central Distributor to obtain your own copy of these files.
 
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Internet Citation: 1993-2002 Nationwide Inpatient Sample (NIS) Supplemental Discharge-Level Files Healthcare Cost and Utilization Project (HCUP). January 2018. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/nation/nis/nistrends2.jsp.
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Last modified 1/18/18