by Sue Bowman, RHIA, CCS
A classification is a system that groups together similar diseases and procedures and organizes related entities for easy retrieval.1 Since a single classification system cannot encompass all types of healthcare information or provide the level of detail desired for various uses of healthcare data, multiple classifications have been developed to meet specific user requirements. This has been an issue for years. As far back as 1856, Victorian medical statistician William Farr stated:
Classification is a method of generalization. Several classifications may, therefore, be used with advantage; and the physician, the pathologist, or the jurist, each from his own point of view, may legitimately classify the diseases and the causes of death in the way that he thinks best, adapted to facilitate his inquiries and to yield general results.2
The International Classification of Diseases (ICD) is intended to meet the requirement for diagnostic information for general purposes. However, in order to accommodate the needs of classification system users who desired additional types of data besides the data traditionally covered in the ICD, the World Health Organization (WHO) developed the concept of a Family of International Classifications (FIC), with the ICD and the International Classification of Functioning, Disability, and Health (ICF) serving as the core classifications. ICD does not include sufficient detail for some specialties, and sometimes information or different attributes of the classified conditions may be needed.
The WHO-FIC provides a framework to code a wide range of information about health (e.g., diagnoses, functioning and disability, reasons for contact with health services) and uses a standardized common language permitting communication about health and healthcare across the world in various disciplines and sciences. These classifications provide a valuable tool for describing and comparing the health of populations in an international context. Classification systems in the WHO-FIC include those that are derived from or related to ICD and serve special niches or needs, including primary care, clinical specialties, and clinical interventions (procedures). Specialty-based adaptations in the family include oncology (ICD-O-2), dentistry and stomatology, psychiatry, dermatology, pediatrics, and rheumatology and orthopedics. This article will discuss a few of the members of the WHO-FIC.
The tenth revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) is the latest in a series formalized in 1893 as the Bertillon Classification or International List of Causes of Death. The title has been amended from previous versions (International Statistical Classification of Diseases) to clarify the content and purpose and reflect the progressive extension of the scope of the classification beyond diseases and injuries.
The North American Collaborating Center (NACC), officially known as the WHO Collaborating Center for the Classification of Diseases for North America, represents the US and Canada in international activities related to study and revision of ICD. Located at the National Center for Health Statistics (NCHS), NACC maintains liaison with WHO on US and Canadian government use, implementation, and maintenance of the FIC. It coordinates activities in three major aspects of classification: mortality, morbidity, and disability. NACC works with the other WHO collaborating centers and related offices to promote and coordinate ICD and ICF applications.
In the US, NCHS is responsible for ICD use in mortality statistics in collaboration with the states. Development and use of the clinical modification of ICD and related classifications for morbidity applications are a shared responsibility with the Centers for Medicare and Medicaid Services (CMS), with NCHS taking the lead for diagnoses and CMS dealing with procedures.
ICD was originally developed as a way to collect data on causes of death. As revisions were developed, there was growing recognition of the need to consider classifications from a broader perspective. It was recognized that the classification of illness and injury was closely linked with the classification of causes of death.3 The purpose of the ICD is to permit the systematic recording, analysis, interpretation, and comparison of mortality and morbidity data collected in different countries or areas and at different times. ICD allows international comparison of the health status of population groups and the monitoring of the incidence and prevalence of diseases and other health problems. ICD-10 promotes international comparability in the collection, classification, processing, and presentation of mortality and morbidity statistics.
The US is required to use ICD for the classification of diseases and injuries under an agreement with WHO. Since 1999 the US has used ICD-10 to report mortality data. However, ICD-10 was not adopted in the US for morbidity reporting purposes because a technical advisory panel recommended that a clinical modification (ICD-10-CM) be developed. A draft of ICD-10-CM has been completed, but the implementation date is still unknown, as the federal rule-making process necessary for implementation of a new code set under HIPAA has not yet been initiated.
Like ICD-10, ICF is a core classification in the WHO-FIC. Where ICD-10 provides users an etiologic framework for the classification of diseases, disorders, and other health conditions, ICF classifies functioning and disability associated with health conditions. ICD-10 and ICF are complementary classifications, and WHO encourages users to use both systems together to create a broader and more meaningful picture of the health of individuals and populations. Information on mortality (provided by ICD-10) and information about health and health-
related outcomes (provided by ICF) can be combined to provide more complete information on population health.
Developed by WHO, ICF represents a revision of the International Classification of Impairments, Disabilities, and Handicaps (ICIDH). The focus of ICIDH was “consequences of disease,” whereas the focus of ICF is “components of health.” ICF is a classification of health and health-related domains that describe body functions and structure, activities, and participation. Since an individual’s functioning and disability occur in a context, ICF also includes a list of environmental factors.
ICF provides a common language for describing health, functioning, and disability. ICF is a multipurpose classification designed to serve various disciplines and different sectors. Its intended to:
- Provide a scientific basis for understanding and studying health and health-related states, outcomes, and determinants
- Establish a common language for describing health and health-related states in order to improve communication between different users
- Permit comparison of data across countries, healthcare disciplines, services, and time
- Provide a systematic coding scheme for health information systems
WHO is encouraging application of the ICF internationally not only as a classification tool, but also as a framework for social policy, research, education, and clinical practice.
The US and Canada have been actively involved in the revision of ICF. Since 1993 revision activities in these countries have been conducted under the auspices of NACC.
NACC sponsors several ongoing ICF activities, such as the development of Web-based training for ICF and the production of internationally comparable disability tabulations from five national disability surveys back-coded to ICF.
In 2001 the National Committee on Vital and Health Statistics (NCVHS) Subcommittee on Populations submitted a report titled “Classifying and Reporting Functional Status” to the secretary of Health and Human Services (HHS). This report was the result of a review on the feasibility of including functional status data in administrative records. ICF is described in the report as a promising approach to coding functional status information in computerized patient records and standardized data sets. NCVHS recommended that the feasibility of using ICF as a mechanism for collecting functional status information be evaluated.4 The Institute of Medicine (IOM) also concluded that ICF is a promising source for standardized representation of functional status and outcome reporting and further investigation and research is warranted.5
The International Classification of Primary Care (ICPC), developed by the World Organization of Family Doctors, is a classification designed for the collection and analysis of patient data and clinical activity in general and family practice and primary care. It was designed as an epidemiological tool to classify data about three important elements of a healthcare encounter: reason for encounter from the patient’s point of view; assessment (diagnoses or problems) described from the healthcare provider’s perspective; and process of care (decision, action, or plans). Although ICPC was originally designed for paper-based data collection and analysis, its use has spread rapidly to electronic health record systems. ICPC-2 (version 2) is available in electronic format (ICPC-2-E).
ICPC has gradually received increasing world recognition as an appropriate classification for general practice and primary care and has been used extensively in some parts of the world, notably Europe and Australia. For example, in Belgium, the inclusion of ICPC will soon be one of the criteria for accreditation of general practitioners’ electronic medical record systems. In the Netherlands, virtually all official data on morbidity in family practice are coded with ICPC, and its use is mandatory in electronic prescribing systems. WHO has accepted ICPC into the WHO-FIC as a related classification to be used for health information recording in primary care. Maps have been developed between ICPC-2 and ICD-10 and SNOMED CT.
IOM has concluded that ICPC warrants further investigation and research into its ability to represent the data needs of the office practice clinician. A collaborative project titled “Applied Strategies for Improving Patient Safety,” sponsored by the Agency for Healthcare Research and Quality, aims to analyze the causes and effects of adverse events in primary care and reduce the incidence of errors and is using ICPC as its classification system.
The International Nomenclature of Diseases (IND) is also part of the WHO-FIC. The primary objective of the IND is to provide a single recommended name for each disease entity. It is the element of grouping that distinguishes a statistical classification from a nomenclature, which must have a separate title for each known disease entity. Each disease or syndrome for which a name is recommended is defined as unambiguously and as briefly as possible. A list of synonyms appears after each definition. To the extent possible, IND provides the set of recommended terms and synonyms that correspond to the entries classified in the ICD codes.
- Brouch, Kathy. “AHIMA Project Offers Insights into SNOMED, ICD-9-CM Mapping Process.” Journal of AHIMA 74, no. 7 (2003): 52–55.
- Sixteenth Annual Report. Registrar General of England and Wales, London, 1856.
- AHIMA. “ICD-10 Overview: Mortality Reporting.” Online course. Available online at
- National Committee on Vital and Health Statistics. “Classifying and Reporting Functional Status.” Available online at www.ncvhs.hhs.gov/010716rp.htm.
- Institute of Medicine. “Patient Safety: Achieving a New Standard for Care.” November 20, 2003. Available online at www.iom.edu/reports.asp.
Sue Bowman (firstname.lastname@example.org) is director of coding policy and compliance at AHIMA.
Bowman, Sue. "ICD-10: All in the Family." Journal of AHIMA 75, no.10 (Nov-Dec 2004): 62-63.