P0645 CDAI underestimates disease activity in overweight patients with Crohn’s Disease when compared to endoscopic assessment
Authors: Campbell I , Brownson E , Wirz A , Seenan J P , MacDonald J , Gerasimidis K 
Published: January 2025

Abstract

Background
The Crohn’s Disease Activity Index (CDAI) score was developed in response to the need for a numerical index to describe disease activity in Crohn’s Disease (CD), to allow a uniform approach to clinical disease assessment.1
An important component of CDAI is body weight, with higher scores allocated to those below ideal body weight. However CD is no longer typically associated with low body weight; in a recent multicentre study 29% of the CD patients were overweight, and 18% obese.2 CDAI may therefore not perform as well in the overweight patient with CD.
We aimed to assess the correlation between CDAI and endoscopic assessment using the Simple Endoscopic Score in Crohn’s Disease (SES-CD) in a cohort of CD patients undergoing- ileocolonoscopy for evaluation of disease activity.

Methods
Patients with a known diagnosis of CD attending for ileocolonoscopy were identified prospectively. SES-CD was recorded, and clinical assessment and blood sampling to calculate CDAI score was carried out. Demographics including sex and disease phenotype (using Montreal classification) were collected. Correlations between groups were analysed using Spearman’s rank and paired t-tests.

Results
52 patients were included, of whom 27 were female. Three patients had isolated ileal disease, 27 isolated colonic disease, and 22 ileo-colonic disease. Median BMI was 23.6 (21.5-27.7). Median CDAI was 141 (IQR 66.8-207.8). Median SES-CD was 4 (IQR 0-12).
A positive correlation was demonstrated between CDAI and SES-CD (p=&lt;0.001, r=0.217). This remained significant when grouped by disease location.
18 patients were overweight (BMI of ≥25). There was no significant difference in the mean SES-CD between those with a BMI &lt;25 and ≥25. Despite the two groups having comparable levels of disease activity at colonoscopy, the CDAI was significantly higher in the BMI &lt;25 group (p=0.05).
There were ten patients in the obese category (BMI ≥30). This group demonstrated significantly more active disease at colonoscopy than those with a BMI &lt;30 with a median SES-CD of 14, but there was no significant difference in CDAI between the two groups.

Conclusion
These results confirm a positive correlation between CDAI and SES-CD in patients with CD in our cohort. However, despite having comparable median SES-CD scores, those with a normal BMI had significantly higher CDAI score than those who are overweight. This suggests that CDAI may under-estimate disease activity in overweight patients with CD, calling in to question the future role of CDAI as both a clinical and research tool given increasing rates of obesity globally. Further analysis is required with a larger, multinational patient cohort to confirm these findings.

References
1.Best WR, Becktel JM, Singleton JW, Kern F Jr. Development of a Crohn’s disease activity index. National Cooperative Crohn’s Disease Study. Gastroenterology. 1976;70(3):439-444.
2.Lomer MCE, Cahill O, Baschali A, et al. A multicentre Study of Nutrition Risk Assessment in Adult Patients with Inflammatory Bowel Disease Attending Outpatient Clinics. Ann Nutr Metab. 2019;74(1):18-23. doi:10.1159/000495214