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Clinical Classifications Software (CCS) for ICD-9-CM Fact Sheet

Clinical Classifications Software (CCS) for ICD-9-CM Fact Sheet

The Clinical Classifications Software (CCS) for ICD-9-CM 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.


Developed at the Agency for Healthcare Research and Quality (AHRQ), the Clinical Classifications Software (CCS) is a tool for clustering patient diagnoses and procedures into a manageable number of clinically meaningful categories. CCS offers researchers the ability to group conditions and procedures without having to sort through thousands of codes. This "clinical grouper" makes it easier to quickly understand patterns of diagnoses and procedures so that health plans, policy makers, and researchers can analyze costs, utilization, and outcomes associated with particular illnesses and procedures.

CCS collapses diagnosis and procedure codes from the International Classification of Diseases, 9th Revision, Clinical Modification (IDC-9-CM), which contains more than 14,000 diagnosis codes and 3,900 procedure codes. Without the CCS tool, the large number of ICD-9-CM codes makes statistical analysis and reporting difficult and time-consuming.

The CCS was formerly known as the Clinical Classifications for Health Policy Research (CCHPR).
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Clinical Classifications Software can be used with all clinical data that are coded using ICD-9-CM codes. CCS is used in a variety of ways:
  • Managed care plans utilize CCS to rank hospitalizations by type of condition. One managed care plan used CCS to examine numbers of cases, length of stay, and total costs, to better understand which conditions and procedures were associated with the highest resource use.
  • Insurers use CCS to develop clinically-based utilization profiles. For example, one insurer integrated CCS into in-house software that develops profiles of patient populations and purchasers.
  • Researchers use CCS to explore the types of conditions and procedures that are most frequent in their study populations or to compare alternative treatments for similar conditions. In one study of differences in use of procedures among payers, CCS procedure categories provided a convenient grouping scheme.
  • Researchers also use CCS in risk adjustment models and as a way to predict future health resource utilization. Investigators in one study found that categorizing patients using CCS predicted more than 40 percent of the subsequent year's medical expenses.
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CCS consists of two related classification systems, single-level and multi-level, which are designed to meet different needs. Single-level CCS is most useful for ranking of diagnoses and procedures and for direct integration into risk adjustment and other software. Multi-level CCS is most useful when evaluating larger aggregations of conditions and procedures or exploring them in greater detail. CCS documentation provides a listing of the ICD-9-CM codes that are included in each CCS diagnosis and procedure category.

Single-level CCS This system classifies all diagnoses and procedures into unique groups. The single-level diagnosis CCS aggregates illnesses and conditions into 285 mutually exclusive categories. Most of these categories are homogeneous; for example, CCS category #1 is "Tuberculosis." Some CCS categories combine several less common, individual conditions, such as CCS category #3, which is "Other Bacterial Infections." Examples of single-level CCS diagnosis categories are illustrated in Table 1.

Table 1. Examples of single-level CCS diagnosis categories

    98. Essential hypertension
    99. Hypertension with complications and secondary hypertension
    100. Acute myocardial infarction
    101. Coronary atherosclerosis and other heart disease

Similarly, the single-level procedure CCS aggregates procedures into 231 mutually exclusive categories, most representing single types of procedures. Some procedures that occur infrequently are grouped together by their clinical or administrative characteristics (for example, operating room vs. nonoperating room). Examples of single-level CCS procedure categories are shown in Table 2.

Table 2. Examples of single-level CCS procedure categories

    43. Heart valve procedures
    44. Coronary artery bypass graft (CABG)
    45. Percutaneous transluminal coronary angioplasty (PTCA)
    46. Coronary thrombolysis

Multi-level CCS The multi-level CCS expands the single-level CCS into a hierarchical system. The multi-level CCS groups single-level CCS categories into broader body systems or condition categories (e.g., "Diseases of the Circulatory System," "Mental Disorders," and "Injury"). It also splits single-level CCS categories to provide more detail. The multi-level system has four levels for diagnoses and three levels for procedures, which provide the opportunity to examine general groupings or to assess very specific conditions and procedures.

Table 3 provides an example of multi-level CCS for diagnoses, showing how single-level category #99 is further subdivided into more specific levels in the multi-level system and how several single-level CCS categories are grouped together to form broader multi-level CCS categories. Table 4 provides an example of the multi-level CCS for procedures.

Table 3. Examples of multi-level CCS diagnosis categories

    7. Diseases of the circulatory system
      7.1. Hypertension
        7.1.1. Essential hypertension [98]
        7.1.2. Hypertension with complications and secondary hypertension [99]
 Hypertensive heart and/or renal disease
 Other hypertensive complications
      7.2. Diseases of the heart

Note: Numbers in brackets refer to single-level CCS categories.

Table 4. Examples of multi-level CCS procedure categories

    7. Operations on the cardiovascular system
      7.1. Heart valve procedures [43]
      7.2. Coronary artery bypass graft [44]
        7.2.1. Bypass of one coronary artery
        7.2.2. Bypass of two coronary arteries
        7.2.3. Bypass of three coronary arteries
        7.2.4. Bypass of four coronary arteries

Note: Numbers in brackets refer to single-level CCS categories
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The CCS code assignments can be downloaded here; complete downloading instructions are also provided at this location.
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Beginning in Fiscal Year 2008, the Clinical Classifications Software for Mental Health and Substance Abuse tool (CCS-MHSA) was permanently integrated into the Clinical Classifications Software tool for diagnoses (CCS). The CCS-MHSA software is no longer updated as a stand-alone tool. To use the MHSA CCS categories, please use the CCS software at the following link:
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Questions regarding the CCS may be directed to HCUP User Support through the following channels:
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Internet Citation: HCUP CCS Fact Sheet. Healthcare Cost and Utilization Project (HCUP). January 2012. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 1/9/12