DIMENSIONALITY AND HIERARCHICAL STRUCTURE OF DISABILITY MEASUREMENT

Since the D-code of the International Classification of Impairments, D isabilities, and Handicaps (ICIDH) in its full form has proven to be i mpractical, an instrument based on a selection of 28 items is used to measure disability in Dutch patients undergoing rehabilitation. The it ems are categorized into 5 domains of physical, activities of daily li ving (ADL), social, psychological, and communicative activity. Measure ment is made on a 4-point scale ranging from 0 (not disabled) to 3 (se verely disabled). As a result of the ordinal character of the rating, statistical and mathematical manipulations of the scores are complicat ed. The aim of this study was to obtain more insight in the dimensiona lity and hierarchical structure of the items, to overcome problems in comparing disability between items, between patients, and within patie nts between different moments in time. Mokhen scale analysis of the di sability scores from 1,967 rehabilitation inpatients showed that the 2 8 items constitute hierarchical scales. However, categorization of the items into the 5 original domains was not replicated. Five other scal es or dimensions were investigated, measuring the level of extended AD L, extended psychological, fine motoric, work/leisure, and hearing/see ing activity, respectively. The number of items per dimension ranges f rom 14 in the extended ADL dimension to 2 each in the work/leisure and hearing/seeing dimensions. Although each disability item may be of im portance in clinical case management, a reduced set of extended ADL it ems suffices to describe the disability level in this dimension for ep idemiological research purposes. The other dimensions need further spe cification to provide reliable and sensitive measuring of disability. (C) 1995 by the American Congress ofliehabilirarion Medicine and the A merican Academy of Physical Medicine and Rehabilitation