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The study was designed to foster close collaboration among national and international experts, including gastroenterologists, specialists, and private practitioners within the study area. Patients were enrolled prospectively over a 4-year period, from January 1, 1990, to December 31, 1993, based on established international diagnostic criteria and a follow-up protocol encompassing 1, 5, 10, 20, and 30-year intervals. The consortium operated through a bidirectional communication network connecting primary and secondary specialized hospitals, encompassing general hospitals and research laboratories. In 2017, the IBSEN III study was launched to facilitate a comparison of clinical and epidemiological outcomes with those of the original IBSEN study, involving an expanded catchment area and more extensive clinical and molecular assessments of the cohort. 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