Use of a medical records linkage system to enumerate a dynamic population over time: the Rochester epidemiology project.

The Rochester Epidemiology Project (REP) is a unique research infrastructure in which the medical records of virtually all persons residing in Olmsted County, Minnesota, for over 40 years have been linked and archived. In the present article, the authors describe how the REP links medical records from multiple health care institutions to specific individuals and how residency is confirmed over time. Additionally, the authors provide evidence for the validity of the REP Census enumeration. Between 1966 and 2008, 1,145,856 medical records were linked to 486,564 individuals in the REP. The REP Census was found to be valid when compared with a list of residents obtained from random digit dialing, a list of residents of nursing homes and senior citizen complexes, a commercial list of residents, and a manual review of records. In addition, the REP Census counts were comparable to those of 4 decennial US censuses (e.g., it included 104.1% of 1970 and 102.7% of 2000 census counts). The duration for which each person was captured in the system varied greatly by age and calendar year; however, the duration was typically substantial. Comprehensive medical records linkage systems like the REP can be used to maintain a continuously updated census and to provide an optimal sampling framework for epidemiologic studies. There is a long tradition of using medical records linkage techniques to create extensive research databases (1). Among English-speaking countries, research databases have been implemented in the United Kingdom (2–6), Australia (7), and Canada (8, 9). However, similar databases have been more limited in the United States because of the lack of a national health system. Only in recent years have attempts been made at the federal level to create publicly accessible databases for research (10). However, these efforts have been hindered by equally strong trends toward strict confidentiality of medical record information (11). Even if national databases become available to investigators , they will lack historical depth and will not be able to answer long-term questions of public health relevance. By contrast, the Rochester Epidemiology Project (REP) is a rare example of a medical records linkage system in the United States that has almost half a century of activity. The REP has linked and archived the medical records of virtually all persons residing in Olmsted County, Minnesota, for over 40 years, has maintained an electronic index of medical diagnoses and surgical interventions, and has archived all addresses and demographic information …