The validation of an informant screening test for irreversible cognitive decline in the elderly: performance characteristics within a general population sample

The performance characteristics of an informant screening test for senile dementia were evaluated within a community-dwelling sample of 583 elderly persons in the Bordeaux region of France. Receiver operating characteristics analysis indicated that although the test performs less well within this context than within a previous case-control study, it nonetheless retains high discriminability. A specificity of 90% and a sensitivity of 79% for the detection of diagnosed senile dementia were obtained with a cutoff point of 24/25. The discriminability of the test was not affected by level of education. The study demonstrates the necessity of adjusting the cutoff point of dementia screening instruments according to the estimated prevalence rate of dementia in the target population. The potential utility of the instrument as a method of detecting dementia by postal survey and in cross-cultural research is discussed.