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NIS Description of Data Elements
The NIS is set of longitudinal hospital inpatient databases included in the HCUP family. These databases are created by AHRQ through a Federal-State-Industry partnership.
 
KEY - Unique record identifier
 
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes
 

KEY contains a unique record identifier. Beginning in the 1998 data, all HCUP databases are sorted by KEY.

KEY can be used to link within a HCUP database, such as linking records in the Core and Charges files in the SID.

KEY can be used to link across HCUP databases within a data type, i.e., link records in the SID to records in the NIS.

KEY is a unique record identifier and not a person identifier. KEY cannot be used to link records between HCUP inpatient and ambulatory surgery files.

KEY replaces the database-specific record identifiers used in the 1988-1997 HCUP databases (SEQ, SEQ_SID, and SEQ_ASD).

KEY is included as the unique record number for the 2000 KID. RECNUM is the unique record number for the 1997 KID, 2003 KID, and subsequent years.

The length of the value of KEY was increased from 14 characters to 15 characters starting in the 2011 HCUP databases. KEY is loaded into SAS, SPSS, and Stata as a numeric data element.

 
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Uniform Values
VariableDescriptionValueValue Description
KEYUnique record identifierPrior to 2011: 14(n), starting in 2011: 15(n)Unique record identifier
 
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State Specific Notes
None
 
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Internet Citation: HCUP NIS Description of Data Elements. Healthcare Cost and Utilization Project (HCUP). September 2008. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/vars/key/nisnote.jsp.
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Last modified 9/17/08