. "Conceptual Issues in the Measurement of Work Disability." The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press, 2002.
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The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs
that, in principle, this system provides a scheme for coding and manipulating data on the consequences of health conditions. This classification and the related model of disablement are being revised and have been named ICIDH-2. At the time of this writing (April 1999), a first, beta draft has been circulated for comment (WHO, 1997), and the beta-2 draft is in the final stages of production. The beta-2 draft revised classification will then undergo 2 years of field testing before the final version is prepared for ratification by the WHO. The changes in the definitions and conceptual model that are being recommended in the process of revision to get ICIDH-2 are discussed below. The U.S. National Center for Health Statistics and the Centers for Disease Control and Prevention have served as the lead U.S. agencies in the international ICIDH revision process.
The first component of the ICIDH-1 model is impairment, which is defined as follows:
In the context of health experience, an impairment is any loss or abnormality of psychological, physiological, or anatomical structure or function. (WHO, 1980, p. 27)
This definition is similar to Nagi’s definition of impairment, but it also includes some of Nagi’s notions of pathology. Just as Nagi’s impairment is focused on organs or organ systems, impairment as defined here is very much concerned with the function and structure of the body and its components. The ICIDH-2 definition is similar:
Impairment is a loss or abnormality of body structure or of a physiological or psychological function. (WHO, 1997, p. 15)
Huge confusion arises because the ICIDH-1 also uses the word disability, but with a slightly different meaning from the Nagi definition of the term. The ICIDH-1 defines disability as follows:
In the context of health experience, a disability is any restriction or lack (resulting from an impairment) of ability to perform an activity in the manner or within the range considered normal for a human being. (WHO, 1980, p. 28)
The focus of this definition is very much on the activities carried out by the person. Further understanding of what is included in this definition can be gained by inspection of the associated classification (WHO, 1980, 1997). The activities included range from simple functional activities, such as gripping and holding and maintaining and changing body positions, to more complex activities, such as those related to self-care