[Reclassification of the diagnosis in inflammatory bowel disease based on a retrospective analysis]

To assess the cumulative frequency and patterns of diagnostic reclassification in inflammatory bowel disease (IBD).

A single-center retrospective longitudinal cohort study was conducted at the Department of Gastroenterology, Peter the Great Clinic, Mechnikov North-Western State Medical University. The study included 800 patients with an established diagnosis of IBD. Grounds for diagnostic reclassification were analyzed. The primary endpoint was the cumulative frequency of diagnostic reclassification. Secondary endpoints included patterns of reclassification in patients initially diagnosed with unclassified IBD and ulcerative colitis (UC), median time to diagnostic revision, the clinical and morphological grounds for reclassification.

During follow-up, diagnostic reclassification occurred in 17.6% of cases (n=141). Among reclassified patients, the initial diagnosis was IBDU in 16.3% (n=23) and UC in 83.7% (n=118). In 93.6% of cases (n=132), reclassification resulted in Crohn's disease (CD) (95% CI 88.2-97.0); in 9 patients, the final diagnosis was unknown due to missing data. The median time from the initial diagnosis to reclassification was 42.0 months [16.0; 99.0]. The most common reason for diagnostic revision was the identification of segmental involvement: 50.0% (7/14) among patients initially classified as IBDU and 63.6% (75/118) among those initially diagnosed with UC (p=0.386). In the presence of a stricture, the median time to reclassification was 96 months [37.0; 186.0].

Diagnostic reclassification in patients with IBD is a prolonged and clinically meaningful process. The findings support the possibility of diagnostic reassessment in patients initially diagnosed with UC or IBDU. In clinical practice, when establishing an IBD diagnosis - particularly UC - it is important to consider the potential for reclassification, and when indications for revision are present, to document the fact of reclassification.