The diagnosis of dementia.

The diagnosis of dementia in the elderly has important personal and social consequences, and a small proportion of cases initially diagnosed may be reversible. An understanding of the operating characteristics and cost-effectiveness of clinical signs and symptoms and of laboratory investigations in the diagnosis of dementia is needed to diagnose accurately yet contain costs. Using published criteria, we critically appraised the current scientific literature on the diagnosis of dementia. The articles that essentially satisfied our criteria suggested that duration and severity of dementia best predicted reversibility and the need for computed tomography of the head. A decision rule may be used to select among a number of investigations now advocated as routine in diagnosing dementia, with little or no risk of missing clinically significant diagnoses and with appreciable cost savings. The reversibility of dementia may not be as major an issue as previously believed, since most instances may be early, atypical presentations of Alzheimer-type dementia.