The International Classification of Functioning, Disability, and Health (ICF) is an example of a terminology coding system developed to meet a specific need. ICF is one of the families of classifications developed and maintained by the World Health Organization (http://www.who.int). The aims of the developers of the ICF were to provide a scientific basis for understanding the distribution and determinants of health and health-related states; establish a common language in order to improve communication among users of such data; permit comparisons on functioning, disability, and health across countries, providers, settings, and programs, and provide a coding scheme for health information systems.11 ICF was included in this study because of its emphasis on functional status (an important concept at least in long-term care) and the potential applicability of this terminology to persons in nursing homes.
An example of how ICF codes might be used follows. The ICF code "d4500" refers to "walking short distances." A performance qualifier can be added to this code by adding a fifth digit to the code. For example, "d4500.3" refers to "moderate restriction in performance of walking short distances." A capacity qualifier could be added to this code by adding a sixth digit; for example "d4500._3" refers to "severe capacity limitation in walking short distances."
The ICF is structured around a hierarchical classification of the domain of functioning, disability and health, grouping concepts and associated terms within the domain according to common characteristics or attributes. At the highest level are two broad classes, functioning and disability, and contextual factors. These two broad classes subsume other lower level classes. Qualifiers indicate the magnitude and/or direction of change in body function and structure, capacity and performance estimates related to activities and participation, and facilitators or barriers related to environmental factors. Users may combine terms across axes in order to create profiles of an individual's functioning. While coding rules are published, there is no formal logic available to support such compositions.
In July 2001 the NCVHS reported to the Secretary of Health and Human Services on uniform coding for functional status.12 NCVHS noted that while functional status information is recognized as essential for fostering the goals of healthy people and healthy populations, such information is often missing from clinical notes. The Committee further recommended the use of a uniform code set and classification system for concepts within the domain of functional status. The NCHS said that an internationally agreed upon classification and coding system was needed to support health care decision making, and that the ICF was the only viable code set presently available. However, the Committee also noted that intense work is needed to examine issues related to the ICF's adequacy, reliability, and validity before any recommendations are adopted about its widespread implementation in PMRI systems. Presently, the ICF is distributed as a book or CD, and a browser is available on the web (http://www3.who.int/icf/onlinebrowser/icf.cfm). The WHO made an electronic copy of the ICF table available for this study.