Peripheral Blood Eosinophilia at Diagnosis of Inflammatory Bowel Disease Is Associated with Severe Disease Course; A Nationwide Study From the epi-IIRN Cohort.

Background & aims: We conducted this nationwide study to evaluate the association between peripheral blood eosinophilia (PBE) and long-term outcomes in children and adults with inflammatory bowel diseases (IBD).

Methods: Data from the epi-IIRN cohort, a validated population-based IBD database, included patients diagnosed between 2005-2020 who had an eosinophil count at diagnosis, and those of non-IBD controls. PBE was defined as an eosinophil count of >0.5 X109/L Severe disease course was defined as corticosteroid dependency, use of ≥2 biologics from different classes, or surgery. Time-to-outcomes, including severe disease course, was determined by Cox proportional hazard models.

Results: Included were 28,133 patients (15,943 Crohn's disease [CD] and 12,190 ulcerative colitis [UC]), and 28,724 non-IBD controls. The prevalence of PBE was 13% in the IBD group and 5% in controls (P < .001). PBE was more prevalent in UC (16.1%) compared to CD (10.6%, OR=1.52 (95%CI 1.42-1.63); P < .001) and in pediatric-onset (23.5%) compared to adult-onset (11%) IBD (OR=2.14 (1.97-2.31); P <.001). In a multivariate analysis, PBE was a predictor of severe disease course in IBD (hazard ratio [HR]=1.49, 95%CI 1.38-1.62, P < .001). PBE also predicted time-to-hospitalization (HR=1.24, 95%CI 1.19-1.30), use of corticosteroids (HR=1.32, 95%CI 1.28-1.36), corticosteroid dependency (HR=1.37, 95%CI 1.31-1.43), and need of biologics (HR=1.27, 95%CI 1.21-1.33).

Conclusion: In this largest nationwide study, PBE predicted severe IBD course. These findings support the use of PBE as a marker of adverse outcome of IBD and as a potential target for future therapies.