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Changes in inflammatory bowel disease subtype during follow-up and over time in 44,302 patients.
Everhov, ÅH, Sachs, MC, Malmborg, P, Nordenvall, C, Myrelid, P, Khalili, H, Elmberg, M, Ekbom, A, Askling, J, Jakobsson, G, et al
Scandinavian journal of gastroenterology. 2019;(1):55-63
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Abstract
AIM: To investigate inflammatory bowel disease (IBD) register-based subtype classifications over a patient's disease course and over time. METHODS We examined International Classification of Diseases coding in patients with ≥2 IBD diagnostic listings in the National Patient Register 2002-2014 (n = 44,302). RESULTS 18% of the patients changed diagnosis (17% of adults, 29% of children) during a median follow-up of 3.8 years. Of visits with diagnoses of Crohn's disease (CD) or ulcerative colitis (UC), 97% were followed by the same diagnosis, whereas 67% of visits with diagnosis IBD-unclassified (IBD-U) were followed by another IBD-U diagnosis. Patients with any diagnostic change changed mostly once (47%) or twice (31%), 39% from UC to CD, 33% from CD to UC and 30% to or from IBD-U. Using a classification algorithm based on the first two diagnoses ('incident classification'), suited for prospective cohort studies, the proportion adult patients with CD, UC, and IBD-U 2002-2014 were 29%, 62%, and 10% (43%, 45%, and 12% in children). A classification model incorporating additional information from surgeries and giving weight to the last 5 years of visits ('prevalent classification'), suited for description of a study population at end of follow-up, classified 31% of adult cases as CD, 58% as UC and 11% as IBD-U (44%, 38%, and 18% in children). CONCLUSIONS IBD subtype changed in 18% during follow-up. The proportion with CD increased and UC decreased from definition at start to end of follow-up. IBD-U was more common in children.