Early Prediction of Primary Non-Response to Infliximab in Crohn's Disease Using Routinely Available Clinical and Week 2 Laboratory Indicators: A Two-Center Real-World Cohort Study

Purpose

Primary non-response (PNR) occurs in a subset of patients with Crohn's disease (CD) after infliximab (IFX) induction therapy and remains challenging to identify early. This study aimed to develop and perform preliminary external validation of an early PNR risk stratification model using routinely available clinical and Week 2 laboratory indicators. Patients and methods: This two-center real-world retrospective cohort study included patients with CD receiving IFX induction therapy from January 2019 to September 2025. Center 1 served as the derivation cohort and Center 2 as the external validation cohort. Model 2C, incorporating complicated disease behavior, Week 2 C-reactive protein (CRP), and Week 2 albumin, was developed using multivariable logistic regression. Model performance was assessed using discrimination, calibration, and overall prediction accuracy. Bootstrap internal validation was performed in the derivation cohort, and the model formula and prespecified fixed cutoff were applied unchanged to the external validation cohort.