Evaluation of the Correlation of Calprotectin and SES-CD Score at the Time of Diagnosis and Follow-up After Diagnosis in Pediatric Patients With Crohn's Disease in Korea.

BACKGROUND: Crohn's disease (CD) requires reliable tools for monitoring intestinal inflammation. Fecal calprotectin (FC) has emerged as a promising non-invasive biomarker. This study aimed to evaluate the correlation between FC and endoscopic activity in pediatric CD confined to the colon and to establish FC cutoff values corresponding to disease severity and remission. METHODS: We conducted a multicenter, retrospective, cross-sectional study including 154 pediatric patients (< 19 years) with Paris classification L2, B1 CD from 15 centers in Korea (2017-2022). Simple Endoscopic Score for Crohn's Disease (SES-CD) and FC were assessed simultaneously at diagnosis and follow-up. RESULTS: At diagnosis, the median FC was 1,355.0 mg/kg and SES-CD 14.0, with 39.6% classified as severe. At follow-up, the median FC was 126.0 mg/kg and SES-CD 2.0, with 50.7% achieving remission. FC correlated most strongly with SES-CD (r = 0.56, P < 0.001). Receiver operating characteristic (ROC) analysis showed acceptable diagnostic accuracy (area under the ROC curves of 0.785 at diagnosis and 0.738 at follow-up). Optimal FC cutoffs were 1,585.0 mg/kg for predicting severe disease (sensitivity 73.8%, specificity 74.2%) and 195.0 mg/kg for predicting remission (sensitivity 78.2%, specificity 61.8%). CONCLUSION: FC strongly correlates with endoscopic activity in pediatric colonic CD, surpassing clinical indices and serum markers. The identification of clinically meaningful cutoff values may reduce the need for repeated endoscopy and support the use of FC as a surrogate marker in real-world pediatric practice.