Dimensionality and hierarchical structure of disability measurement

Abstract

Since the D-code of the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) in its full form has proven to be impractical, an instrument based on a selection of 28 items is used to measure disability in Dutch patients undergoing rehabilitation. The items are categorized into 5 domains of physical, activities of daily living (ADL), social, psychological, and communicative activity. Measurement is made on a 4-point scale ranging from 0 (not disabled) to 3 (severely disabled). As a result of the ordinal character of the rating, statistical and mathematical manipulations of the scores are complicated. The aim of this study was to obtain more insight in the dimensionality and hierarchical structure of the items, to overcome problems in comparing disability between items, between patients, and within patients between different moments in time. Mokken scale analysis of the disability scores from 1,967 rehabilitation inpatients showed that the 28 items constitute hierarchical scales. However, categorization of the items into the 5 original domains was not replicated. Five other scales or dimensions were investigated, measuring the level of extended ADL, extended psychological, fine motoric, work/leisure, and hearing/seeing activity, respectively. The number of items per dimension ranges from 14 in the extended ADL dimension to 2 each in the work/leisure and hearing/seeing dimensions. Although each disability item may be of importance in clinical case management, a reduced set of extended ADL items suffices to describe the disability level in this dimension for epidemiological research purposes. The other dimensions need further specification to provide reliable and sensitive measuring of disability.

Efficiency of Predicting Risk in Word Reading Using Fewer, Easier Letters

“…Hierarchies are a useful convention to studying the relation among items on a given scale, and are especially popular in medical and psychological applications (Kempen, Myers, & Powell, 1995; Watson, Deary, & Austin, 2007; van Boxel, Roest, Bergen, & Stam, 1995), where individuals’ scores on an assessment can be directly related to their ability on the latent construct of interest. Similar to Rasch models, Mokken scales have the advantage that the sum of items scores in a Mokken scale is a measure for the order of the latent trait being identified (Moorer, Suurmeijer, Foets, & Molenaar, 2001).…”

Severity, timing, and structure of disability

“…Dysfunctions in the two zones often arise from very different health problems. Disability scales routinely show that upper-extremity tasks, especially fine motor ones, rank lower than do lower-extremity tasks in a scale, and the items may generate separate scales altogether (van Boxel et al 1995). (5) People with perfect hierarchy produce especially clear results.…”

“…Empirical links between them may be faint in the community-dwelling population, in part because persons with severe degree-of-difficulty tend to exit. Within-task severity has been integrated into some recent statistically-derived disability scales, and they successfully rank both tasks and task-specific degrees of difficulty (Heinemann et al 1993;Kempen et al 1995;1996;Kempen & Suurmeijer 1990;Linacre et al 1994;van Boxel et al 1995;van Buuren & Hopman-Rock 2001). The predictive ability of across-task and within-task severity should be compared; it is likely that both are needed for good prediction.…”

Measurement Models for Reasoned Action Theory

“…One application of causal indicators is measuring physical ability or disability, often motivated by an interest in the evaluation of quality of life in geriatric populations (Fayers et al 1997). For example, Van Boxel and colleagues (Van Boxel et al 1995) measured functional abilities related to daily living (the “Activities of Daily Living” [ADL] item battery) in a hospital sample of rehabilitation patients. The ADL consists of a check list of abilities such as “walking outdoors,” “climbing stairs,” “bathing,” and “lifting.” Similarly, Ringdal and colleagues (Ringdal et al 1999) used a battery of negatively worded dichotomous items such as “need help with eating or dressing,” “trouble taking a long walk,” or “unable to do work or housework” to evaluate functional disabilities in a sample of cancer patients.…”