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Procedure Classes for ICD-9-CM

Procedure Classes

ICD-9-CM codes were frozen in preparation for ICD-10 implementation and regular maintenance of the codes has been suspended. The HCUP Tools for ICD-9-CM should only be used with data for discharges before 10/1/2015.

Procedure Classes are part of the 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.


The Procedure Classes provide users an easy way to categorize procedure codes into one of four broad categories: Minor Diagnostic, Minor Therapeutic, Major Diagnostic, and Major Therapeutic.

Procedure codes for this tool are based on the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), Fifth Edition (Public Health Service and Health Care Financing Administration, 1994). The ICD-9-CM consists of approximately 3,900 procedure codes.

This documentation provides an overview of the following:
  • The categorization scheme used by the Procedure Classes
  • A description of downloadable, electronic files that contain the translation of ICD-9-CM procedure codes into Procedure Classes.
The Procedure Classes files are updated each year. The current version is based on ICD-9-CM procedure codes that are valid for January 1, 1980 through September 30, 2015.
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The Procedure Classes are created to facilitate health services research on hospital procedures using administrative data. This classification system allows the researcher to readily determine if (a) a procedure is diagnostic or therapeutic, and (b) a procedure is minor or major in terms of invasiveness and/or resource use.
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The Procedure Classes assign all ICD-9-CM procedure codes to one of four categories:
  1. Minor Diagnostic - Non-operating room procedures that are diagnostic (e.g., 87.03 CT scan of head)
  2. Minor Therapeutic - Non-operating room procedures that are therapeutic (e.g., 02.41 Irrigate ventricular shunt)
  3. Major Diagnostic - All procedures considered valid operating room procedures by the Diagnosis Related Group (DRG) grouper and that are performed for diagnostic reasons (e.g., 01.14 Open brain biopsy)
  4. Major Therapeutic - All procedures considered valid operating room procedures by the Diagnosis Related Group (DRG) grouper and that are performed for therapeutic reasons (e.g., 39.24 Aorta-renal bypass).
One file is necessary to assign Procedure Classes. This file is provided as an ASCII (DOS text) file. It can be applied to translate ICD-9-CM procedure codes into the four Procedure Classes, and includes three elements: ICD-9-CM procedure codes, ICD-9-CM code labels, and Procedure Class assignments.

The contents of the file are described below:

Filename Purpose
PC2015.CSV Comma-delimited translation file that maps ICD-9-CM procedure codes into Procedure Classes categories.
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The ICD-9-CM codes are revised every October. New codes are added, existing codes are deleted, and definitions of current codes are changed. The four categories are revised annually, in response to ICD-9-CM changes. The current version of the Procedure Classes is valid for the time period January 1, 1980 through September 30, 2015. Using the current Procedure Classes files with data outside this frame period may result in misclassification of ICD-9-CM codes.
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The Procedure Classes translation file lists the ICD-9-CM procedure codes and their corresponding Procedure Classes. The file is in Comma Separated Value format (CSV) and can be viewed in a text editor or using Microsoft Excel. The manner in which this file may be applied varies by the type of software package. For example, in SAS, the files can be used to create a format through the command PROC FORMAT, which translates ICD-9-CM procedure codes into Procedure Classes. In SPSS, the translations can be adapted through the use of COMPUTE and VALUE LABELS statements or a series of RECODES. Sample Stata programs are provided below.

Calculating ORPROC: Users who wish to identify discharges that contain an operating room procedure should follow the basic guidelines below:

  1. The first step is to assign the Procedure Classes indicators to a dataset using the PC tool. This entails creating an array of Procedure Classes flags on each record that is equal in size to the number of procedures on the record. If a user has 15 procedures (PR1-PR15) on a given record, then 15 Procedure Classes flags should be created (PLCASS1-PCLASS15) . Each Procedure Classes indicator would be created using the corresponding procedure code array element (PCLASS5 would be created by examining the fifth procedure - PR5).
  2. Once an array of Procedure Classes flags are made for each record, users should loop through that array to find any instances where a procedure takes place in the Operating Room (PCLASS is 3 or 4). When an OR procedure is found, the ORPROC data element should be set to 1, otherwise it should be 0.
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In practice, ICD-9-CM procedure codes are represented by 3- or 4-character codes with explicit decimals. In the downloadable translation files, ICD-9-CM procedures are represented as 4-character alphanumeric codes with implicit decimals. These alphanumeric codes are enclosed in quotation marks in the translation files. Examples are presented below:

Procedure ICD-9-CM procedure code Alpha code (implicit decimals)
Incision of prostate 60.0 '600 '
Closed biopsy of prostate 60.11 '6011'

To assure that procedure codes are properly processed in the Procedure Classes, the following actions must be taken:
  • Alphanumeric procedure codes must be left-justified.
  • One space must always follow a 3-character procedure code.
  • Trailing blanks should never be zero-padded (i.e., blank spaces following a 3-character procedure code should not be filled with zeroes).
  • Leading zeroes must be preserved; they are significant.
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The HCUP Procedure Classes tool is used in the risk adjustment approach for CMS' readmission measures that are now part of the Hospital Readmissions Reduction Program (HRRP).

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The ASCII (DOS text) files for use with SAS or SPSS are available for download as pc2015.csv.

Stata Procedure Classes Program (ZIP file, 10 KB)

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Questions regarding the Procedure Classes may be directed to HCUP User Support through the following channels:
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Internet Citation: HCUP Procedure Classes. Healthcare Cost and Utilization Project (HCUP). February 2016. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 2/18/16