The construct validity of the clock test in normal and demented adults
Date
1992
Authors
Kurzman, David
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The Clock Test is a multidimensional measure comprised of Clock Drawing, Clock Setting, and Clock Reading. Recently components of this test, which were designed to assess visuospatial construction, visual perception, abstract conceptualization of time, and general cognitive status, have received much empirical attention. The present study examined the following properties of the Clock Test: (a) reliability (i.e., internal consistency), (b) the effect of age, education, and diagnostic group, (c) group differences, and classification of the dimensions of Clock Drawing, and (d) construct validity, or the relationship of the Clock Test to other neuropsychological tests. In addition, a series of Confirmatory Factor Analyses were conducted in order to examine the factor structure of the Clock Test relative to other neuropsychological measures.
The sample consisted of 19 individuals with a diagnosis of non Alzheimer's dementia, 100 individuals with a diagnosis of Possible Alzheimer's disease, 146 individuals with a diagnosis of Probable Alzheimer's disease, 90 individuals who complained of memory problems but were not demented, and 61 normal community-dwelling adults over the age of 50. The participants were further classified into 267 demented and 151 relatively normal adults ranging in age from 54 to 84 years (M = 71.1 years).
Results demonstrated that whereas the Clock Setting (α = .84) and Clock Reading (α = .83) showed high reliabilities for the demented participants, the reliabilities were lower for the not demented adults (α = .84, .57; Clock Setting and Clock Reading, respectively). Unlike the demented adults whose performance was unrelated to age, performance decreased as a function of age for the relatively normal adults. Education was unrelated to performance for both groups of subjects. In addition, differences were observed in the performance of the demented and relatively normal groups, when each of the seven error categories of Clock Drawing were examined separately. Further, only the first category of errors alone was sufficient to classify individuals into their groups, since the remaining categories did not significantly improve the classification of individuals into groups.
When the Clock Test components were compared to a battery of valid and reliable neuropsychological tests, they were correlated positively with the convergent validity measures (r = .27 - .77); in contrast, they did not show a strong relationship, to the discriminant validity measures (I: = .04 - .27). Whereas the pattern of correlations was replicated for the demented participants, they revealed only limited support for the relatively normal group. A Confirmatory Factor Analysis was conducted on a four factor model. This model was tested separately for the demented and not demented groups and although none of the models satisfied a conventional fit, the best-fitting model was one in which the Multi-focus Assessment Scale (MAS) was dropped and various error parameters were free to be estimated.
Discussion focuses on the limitations of the Clock Test as a diagnostic tool for dementia. In addition, suggestions for future research, as well as potential modifications to the Clock Test are proposed.
Description
Keywords
UN SDG 4: Quality Education