In adults with newly diagnosed IBD, what proportion are reclassified from UC to CD within two years of follow-up

What is known

- The closest adult figure comes from a large cohort: among all patients with any diagnostic change over a median 3.8 years of follow-up, 39% of the changes were from UC to CD, and 17% of adults changed diagnosis overall. ¹

What is unknown / caveats

- The excerpts do not report a specific two-year proportion of adults reclassified from ulcerative colitis to Crohn's disease. - That cohort figure is not restricted to a two-year window. - It is expressed as a proportion of diagnostic changes, not as a proportion of all UC patients.

## References

1. Everhov ÅH, Sachs MC, Malmborg P, Nordenvall C, Myrelid P, Khalili H, Elmberg M, Ekbom A, Askling J, Jakobsson G, Halfvarson J, Ludvigsson JF, Olén O. Changes in inflammatory bowel disease subtype during follow-up and over time in 44,302 patients. Scand J Gastroenterol. 2019;54(1):55-63. PMID: 30700170.

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_Draft, generated by the IBDology RAG and not yet clinician-reviewed. Answers are grounded in the retrieved literature listed above; a high faithfulness score means the answer matches its sources, not that the sources are correct._