Passive case-finding for Alzheimer's disease and dementia in two U.S. communities.

Passive surveillance for disease is a public health approach that relies on documentation available within existing health records for the region or community being studied. Its two primary advantages over active case-finding are the lower cost of research and the lower burden on the population under study. The effectiveness of passive case-finding depends on the comprehensiveness of the healthcare coverage in a given community and the adequacy of the available medical records. The Rochester Epidemiology Project has permitted dementia case detection for Olmsted County, Minnesota, using a medical records-linkage system. These data were compared with case ascertainment using direct assessment of individuals in an epidemiological study of the same community. At the Group Health Research Institute, investigators compared dementia and Alzheimer's disease cases detected using an electronic medical record database search with those identified by a parallel active case-finding study. In this article, the advantages and disadvantages of passive case-finding were discussed, and the following conclusion was drawn: the purpose of the study being conducted should determine the case-finding approach that is to be used. Copyright Â