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.

The Chronic Condition Indicator 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.

Contents:

• Overview of the Chronic Condition Indicator
• Purpose
• Description
• Chronic Condition Indicator Files
• Time Period Covered by the Chronic Condition Indicator
• Representation of ICD-9-CM Diagnosis Codes
• Using the Translation Files
• Downloading Information
• Publications Using the Chronic Condition Indicator
• References
• Questions?

The Chronic Condition Indicator provides an easy way for users to categorize ICD-9-CM diagnosis codes into one of two categories: chronic or not chronic. Examples of chronic conditions include conditions such as malignancies, diabetes, most forms of mental illness, hypertension, many forms of heart disease, and congenital anomalies. Non-chronic conditions include conditions such as infections, pregnancy, many neonatal conditions, non-specific symptoms, and injuries. To obtain the entire listing of all conditions view the downloadable file which contains a listing of all ICD-9-CM codes and their assignment to chronic or nonchronic.

Diagnosis codes for this tool are based on the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), Fifth Edition. The ICD-9-CM consists of approximately 14,000 diagnosis codes.

This documentation provides an overview of the following:

• The categorization scheme used by the Chronic Condition Indicator
• A description of downloadable, electronic files that contain the translation of ICD-9-CM diagnosis codes into the Chronic Condition Indicator

The Chronic Condition Indicator is updated each year. The current version is based on ICD-9-CM diagnosis codes that are valid for January 1, 1980 through September 30, 2015.

The Chronic Condition Indicator is created to facilitate health services research on diagnoses using administrative data. This classification system allows researchers to readily determine if a diagnosis is a chronic condition. In addition, the tool groups all diagnoses into body systems so that users can create indicators listing which specific body systems are affected by a chronic condition listed on the record.

The Chronic Condition Indicator categorizes all ICD-9-CM diagnosis codes as chronic or not chronic. A chronic condition is defined as a condition that lasts 12 months or longer and meets one or both of the following tests: (a) it places limitations on self-care, independent living, and social interactions; (b) it results in the need for ongoing intervention with medical products, services, and special equipment (see Perrin et al., 1993). The identification of chronic conditions is based on all 5-digit ICD-9-CM codes. E Codes, or external cause of injury codes, are not classified, because all injuries are assumed to be acute.

The algorithm originated with work reported by Hwang et al (2001) in which selected 3-digit ICD-9-CM codes were classified as chronic conditions. That study employed diagnosis information from the Medical Expenditure Panel Survey (MEPS), which is based on patient self-report and thus lacks the specificity of physician-assigned diagnoses. For Hwang’s study, a physician panel reviewed each diagnosis code that appeared in MEPS data and determined whether the code represented an acute or chronic condition.

Hwang’s method was enhanced for the inpatient data in this study because a large number of conditions had not been coded in MEPS data and thus were not classified as acute or chronic. In addition, a number of ICD-9-CM codes at the 3-digit level had been designated as acute even though they may subsume more specific constituent 5-digit codes of chronic conditions. Thus, each 5-digit code was reviewed by a health services researcher with a clinical background using Hwang’s classification as well as other sources that provided information on the chronicity of specific conditions (Burwell et al, 1997; Elixhauser et al, 1998; Ozminkowski et al, 2000; University of Manitoba, 2000; Wisconsin, 2004).

Disagreements with Hwang’s original classification were resolved in consultation with one of the original physician panel members. As a final step, the assignment of all ICD-9-CM codes was reviewed by an expert medical coder, resulting in the reassignment of some codes.

In general, Hwang's designation of chronic (1) versus not chronic (0) superceded other references. However, there were a number of exceptions:

1. When a 4- or 5-digit code within a 3-digit series reviewed by Hwang is explicitly chronic, the code is designated as chronic (e.g., see chronic viral hepatitis codes 070.22-070.23).



2. When a code was not reviewed by Hwang, one of the other sources was used to decide whether it was chronic or not chronic.



3. When a code was not reviewed by Hwang but is similar to other codes that were reviewed, we followed Hwang's designation (e.g., see the tuberculosis codes).



4. Potentially disabling codes (Burwell et al., 1997), were not considered a determining factor, unless it is clear that it will result in a chronic condition.



5. When an ICD code is listed as "not otherwise specified" or "not elsewhere classified," it is not designated as a chronic condition, unless it is clearly and explicitly a chronic condition (e.g., 246.8 disorders of the thyroid, not elsewhere classified and 246.9 disorder of the thyroid, not otherwise specified).



6. When a code is listed as "history o...," it is not designated as a chronic condition because it is assumed that the condition is no longer active.



7. All congenital anomalies were designated as chronic conditions.



8. All cancers are considered chronic except basal cell carcinomas (173.0-173.9). All benign neoplasms are considered non-chronic except benign neoplasms of the brain, cranial nerves, and cerebral meninges (225.0-225.2). Carcinomas in situ are considered chronic except for skin and cervix. Neoplasms of uncertain behavior are considered non-chronic except neurofibromatosis.

The body system indicator is based upon the chapters of the ICD-9-CM codebook. This indicator may be useful as a means of counting the number of body systems; the indicator is provided for each condition, chronic and not chronic. Alternatively, the Clinical Classifications Software (CCS) may be used in conjunction with the Chronic Condition Indicator in order to obtain a count of the number of relatively discrete chronic conditions.

One file is necessary to assign the Chronic Condition Indicator and to assign ICD-9-CM codes into body systems. This file is provided as an ASCII (DOS text) file. The file can be applied to designate ICD-9-CM diagnosis codes as chronic or non-chronic, or to assign a body system. The tool includes four elements: ICD-9-CM diagnosis codes, ICD-9-CM code labels, Chronic/non-Chronic assignments, and Body System assignments.

The contents of the file are described below:

Filename	Purpose
CCI2015.CSV	Comma-delimited translation file that maps ICD-9-CM diagnosis codes into the Chronic Condition Indicator and into body systems.

The chronic indicator is defined as either 0 - non-chronic condition or 1 - chronic condition.

The body system indicator is divided into the following categories:

1 = Infectious and parasitic disease

2 = Neoplasms

3 = Endocrine, nutritional, and metabolic diseases and immunity disorders

4 = Diseases of blood and blood-forming organs

5 = Mental disorders

6 = Diseases of the nervous system and sense organs

7 = Diseases of the circulatory system

8 = Diseases of the respiratory system

9 = Diseases of the digestive system

10 = Diseases of the genitourinary system

11 = Complications of pregnancy, childbirth, and the puerperium

12 = Diseases of the skin and subcutaneous tissue

13 = Diseases of the musculoskeletal system

14 = Congenital anomalies

15 = Certain conditions originating in the perinatal period

16 = Symptoms, signs, and ill-defined conditions

17 = Injury and poisoning

18 = Factors influencing health status and contact with health services

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. There were no new diagnosis codes for 2015. Using the current Chronic Condition Indicator files with data outside this time period may result in misclassification of ICD-9-CM codes.

In practice, ICD-9-CM diagnosis codes are represented by 3-, 4-, or 5-character codes with explicit decimals. In the downloadable translation files, ICD-9-CM diagnoses are represented as 5-character alphanumeric codes with implicit decimals. These alphanumeric codes are enclosed in quotation marks in the translation files. Examples are presented below:

Diagnosis	ICD-9-CM diagnosis code	Alpha code (implicit decimals)
Old myocardial infarction	412	'412 '
Angina pectoris	4139	'4139 '
Acute myocardial infarction, anterolateral wall, initial	41001	'41001'

To assure that diagnosis codes are properly processed in the Chronic Condition Indicator, the following actions must be taken:

• Alphanumeric diagnosis codes must be left-justified.
• Two spaces must always follow a 3-character diagnosis code.
• One space must always follow a 4-character diagnosis code.
• Trailing blanks should never be zero-padded (i.e., blank spaces following a 3-character diagnosis code should not be filled with zeroes).
• Leading zeroes must be preserved; they are significant.

The Chronic Condition Indicator translation file lists the ICD-9-CM diagnosis codes and their corresponding chronic/non-chronic designation. The file also lists the body type associated with each diagnosis, chronic and not chronic. This CSV file can be viewed in a text editor or by 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 diagnosis codes into the Chronic Condition Indicator/body type. 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 NCHRONIC: Users who wish to determine the number of chronic conditions on a discharge will need to do the following:

1. The first step is to assign chronic condition indicators to a dataset using the CCI tool. This entails creating an array of chronic condition indicators on each record that is equal in size to the number of diagnoses on the record. If a user has 15 diagnoses (DX1-DX15) on a given record, then 15 chronic condition indicators should be created (CHRON1-CHRON15) . Each chronic condition indicator would be created using the corresponding diagnosis array element (CHRON5 would be created by examining the fifth diagnosis- DX5). Users should also assign the CCS diagnosis categories to their data if they are not already present.



2. Once an array of chronic conditions data elements is made for each record, users should loop through said array to find any instances of a chronic condition (CHRONn=1). To avoid double counting of chronic conditions for the same CCS category, users should check the CCS array element that corresponds with a chronic condition against previous CCS array elements to ensure that the CCS value is not repeated. If the same CCS category is not repeated, then the count of chronic conditions should be incremented by one. For example, if the CHRON6 shows a chronic condition, the corresponding CCS (CCS6) should be checked against the previous CCS array elements (CCS1-CCS5) to determine whether the corresponding chronic condition has already been counted.

The translation file for use with SAS or SPSS is an ASCII (DOS text) file and is available for download as CCI2015.CSV.

Stata Chronic Condition Indicator Program (ZIP file, 10 KB)

Chi MJ, Lee CY, Wu SC. The prevalence of chronic conditions and medical expenditures of the elderly by chronic condition indicator (CCI). Archives of gerontology and geriatrics, Epub ahead of print, May 10, 2010. http://www.ncbi.nlm.nih.gov/pubmed/20452688.

Friedman B, Jiang HJ, Elixhauser A, Segal A. 2006. "Hospital costs for adults with multiple chronic conditions." Medical Care Research and Review 63(3): 327-346.

Magnan, Elizabeth. Algorithm for Identifying Patients with Multiple Chronic Conditions (Multimorbidity).http://www.hipxchange.org/comorbidities (accessed June 1st, 2015).

Burwell B, Crown W, Drabek J. (1997). "Children with Severe Chronic Conditions on Medicaid," Report prepared under contract, U.S. Department of Health and Human Services, Office of the Assistant Secretary for Planning and Evaluation (ASPE), Office of Disability, Aging, and Long-Term Care Policy. Report available at website http://aspe.hhs.gov/daltcp/reports/children.htm (accessed November 14, 2005).

Elixhauser A., Steiner C., Harris R., Coffey R.M. 1998. "Comorbidity Measures for Use with Administrative Data," Medical Care 36:8-27.

Hwang, W., Heller, W., Ireys, H., Anderson, G. 2001. "Out-Of-Pocket Medical Spending for Care of Chronic Conditions," Health Affairs 20, no. 6:267-278.

Perrin EC, Newacheck P, Pless IB, Drotar D, Gortmaker SL, Leventhal J, Perrin JM, Stein RE, Walker DK, Weitzman M. 1993. "Issues Involved in the Definition and Classification of Chronic Health Conditions," Pediatrics 91, no. 4:787-793.

Ozminkowski RJ, Smith MW, Coffey RM, Mark TL, Neslusan CA, Drabek J. (2000). "Private Payers Serving Individuals with Disabilities and Chronic Conditions" Report prepared under contract #HHS-100-95-0044, U.S. Department of Health and Human Services, Office of Disability, Aging and Long-Term Care Policy. http://aspe.hhs.gov/daltcp/reports/privpay.htm (accessed November 14, 2005).

University of Manitoba. 2000. Chronic Disease Hospitalizations. An on-line concept dictionary to assist health services researchers with some groups of chronic conditions, http://www.umanitoba.ca/ centres/mchp/concept/dict/chronic_disease.htm. (accessed November 14, 2005).

Wisconsin Department of Health and Family Services provides ICD-9-CM codes for chronic conditions http://www.dhfs.state.wi.us/localdata/chronicconditions/ CHRONICD.HTM (accessed October 18, 2004, no longer active).

Questions regarding the Chronic Condition Indicator may be directed to HCUP User Support through the following channels:

• e-mail: hcup@ahrq.gov
• Phone (toll free): 1-866-290-HCUP.