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The Comorbidity Software is one in 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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Comorbidity software assigns variables that identify comorbidities in hospital discharge records using the diagnosis coding of ICD-9-CM (International Classification of Diseases, Ninth Edition, Clinical Modifications). This document describes the software that creates the comorbidity measures reported by Elixhauser et al. ("Comorbidity Measures for Use with Administrative Data." Medical Care, 1998;36:8-27).
Select to download software. The comorbidity software consists of two SAS computer programs for PCs. Although these programs are written in SAS, they are being distributed in ASCII so that they can be readily adapted to other programming languages. The first program, Creation of Format Library for Comorbidity Groups, creates a SAS format library that maps diagnosis codes into comorbidity indicators. Additional formats are created to exclude conditions that may be complications or that may be related to the principal diagnosis. The second SAS program, Creation of Comorbidity Variables, applies these formats to a data set containing administrative data. This documentation describes three topics:
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The input data file must contain certain elements that are coded in specific ways. These elements are required for the assignment of the comorbidity flags. The flags are 0/1 indicators that note whether individual records include each comorbidity.
The input data set must have the following two variables:
Required Elements of Input File
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Creation of Format Library for Comorbidity Groups
The format program defines a format library that contains the diagnosis screens necessary for the comorbidity analysis. It will be used by Program 2, the comorbidity analysis program.
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Creation of Comorbidity Variables
The analysis program assigns to the inpatient records 0/1 indicators for the comorbidity variables of interest. This program assumes that the input data file conforms to specific variables names, attributes, and coding conventions, as described above.
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ICD-9-CM and DRG coding changes through September 30, 2004, are incorporated into this software. Changes to the Comorbidity Software for FY2004, Version 2.0 are summarized in Table 1. (PDF file, 39 KB)
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Thirty comorbidity variables are created using the comorbidity software, based on the format library. The library contains formats for the ICD-9-CM codes and DRG screens. Construction of these variables is summarized in Table 2. (PDF file, 24 KB)
The original table appeared in the paper by Elixhauser et al (1998). This table has been updated to reflect the ICD-9-CM and DRG updates in the software. | ||||||||||||||||||||
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Questions regarding the CCS may be directed to HCUP User Support through the following channels:
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Additional information is available on the AHRQ Web site. If you have comments, suggestions, and/or questions, please contact hcup@ahrq.gov. |
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Internet Citation: HCUP Comorbidity Software. Healthcare Cost and Utilization Project (HCUP). August 2004. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/toolssoftware/comorbidity/comorbidity.jsp. |
Last modified 8/3/04 |