Assessment of mental competency in community-dwelling elderly

We studied the utility: of a "vignette method" to assess mental competency for decision making on medical treatment and research participation. A vign ette is a description of an imaginary situation in which the subject is ask ed to decide on a proposed treatment or on participation in research. His o r her understanding of the situation and the quality of the reasoning under lying that choice are tested by a short series of questions. Subjects were participants in the Amsterdam Study of the Elderly (AMSTEL), a population-b ased study on cognitive decline and dementia. The sample consisted of elder ly people (70-90 years), who were cognitively intact (n = 176) or had a dem entia syndrome (n = 64; mostly Alzheimer disease). Dementia was diagnosed u sing the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX) schedule. Two vignettes were used as competency assessment instruments. Th e answers to the vignette questions were summed to form a competency score. The reliability (internal consistency) of this score was 0.82 for both vig nettes combined. After dichotomization into competent/incompetent (cutoff a t the fifth centile of the control group), the agreement between the vignet te method and a physician's judgment of competency was poor (kappa = 0.36) in the demented group. There was no agreement whatsoever when subjects with "minimal dementia" (n = 14) were left out of this analysis (kappa = 0.04). As expected, mean competency scores declined with increasing dementia seve rity. A multiple regression analysis showed that mental competency as measu red by the vignette method was determined mainly by recent memory, expressi ve language, and abstract thinking. In the control group the competency sco re was only slightly related to education (r = 0.12) and verbal intelligenc e (r = 0.27). We conclude that the vignette method is a reliable and valid method for the assessment of mental competency in elderly people with cogni tive decline. The vignette method is preferred over a physician's judgment, especially in patients with early dementia.