Because reported disease associations are subject to so many forms of bias, our ability to rigorously evaluate such associations in a population-based setting has become crucial. In addition, with dramatic advances in medical technology and reforms in health care delivery that are now underway, Rochester Project data on the natural history of disease and the long-term outcomes of specific medical interventions are increasingly needed for developing practice guidelines. The unit records for each patient seen at Mayo Clinic contain the details of all inpatient care at its two affiliated hostpitals, every outpatient office or clinic visit including outpatient surgery, all emergency room and nursing home care, all laboratory results, all pathology reports including autopsies and all correspondence concerning each patient. Mayo has maintained the original records of every patient seen since 1907 Currently Mayo has catalogued dossiers for 4.5 million individuals, including referral patients from outside Olmsted County . When the primary physician seeks a consultation from a physician in another clinical department, the consultant's findings are recorded on forms specifically designed for each specialty.
All material is returned to the primary physician for review.
Here it passes through the completion desk where data consolidation occurs, redundant forms are removed, and the forms are arranged in a prescribed order in the dossier. From the completion desk, the dossier is sent to the Section of Medical Information Resources in the Department of Health Sciences Research , where trained nosologists code all diagnoses recorded on the master sheet for the current registration and enter the data into the Mayo Cliic diagnostic index. When indexing is complete, the dossiers are returned to the permanent file to be held until needed. The location of a dossier is carefully monitored by a computerized bar-code system when it is removed from permanent file for a clinical care encounter or for any other purpose. To date, among the more than 4.5 million dossiers that have been created, only some 300 have been lost in over 80 years.