Murthy SK, et al. - This is the first study investigating the utility of administrative data to discriminate different levels of ulcerative colitis (UC) disease burden at diagnosis. Using Ontario health administrative data, researchers developed predictive models of disease burden at diagnosis in UC patients for future use in population-based studies of incident UC cohorts. They characterized macroscopic colitis activity and extent at diagnosis in consecutive adult-onset UC patients diagnosed at The Ottawa Hospital between 2001 and 2012 through chart review. For 587 eligible patients, 20 administrative variables were tested. In adult-onset UC patients, Ontario health administrative data might reasonably discriminate levels of total disease burden at diagnosis. The models should be externally validated before they are widely used in future population-based studies of incident UC cohorts to adjust to the confounding effects of disease burden differences.