Existing Prediction Models of Disease Course in Paediatric Crohn's Disease Are Poorly Replicated in a Prospective Inception Cohort

Background: Several groups have proposed models to predict disease outcomes in paediatric Crohn's disease [CD], notably the RISK, GROWTH, and the Porto group, but none were externally validated. We aimed to explore these predictive models and individual predictors summarised by the PIBD-ahead project in a prospective inception cohort of paediatric CD. Methods: We included children who were diagnosed with CD at two medical centres and followed them at 3 and 12 months thereafter as well as at the last follow-up. Outcomes included steroid-free remission [SFR], surgery, and stricturing/fistulising disease. Results: In all 155 children were included (median follow-up of 31 [16-48] months, 107 [71%] had moderate-to-severe disease). Stricturing and penetrating disease at diagnosis were noted in 34 [22%] and two [1.3%] children, respectively, and these were excluded from the relevant analyses. At 1 year, 10 [8.3%] developed new stricturing disease, two [1.7%] developed penetrating disease, seven [5%] required intestinal surgery, and 15 [10%] required perianal surgery. The sensitivity/specificity/positive predictive value [PPV]/negative predictive value [NPV] of the GROWTH criteria for predicting SFR at 12 months [occurring in 70% of children] were 20%/85%/76%/31% and for surgery at 2 years were 96%/20%/16%/96%, respectively. Strictures were predicted by the RISK model with sensitivity/specificity/PPV/NPV of 33%/73%/18%/86%, respectively. The sensitivity/specificity/PPV/NPV of the Porto criteria to predict surgery were 86%/10%/4%/94%, respectively. None of the Pediatric Inflammatory Bowel Disease-ahead [PIBD-ahead] predictors were associated with surgery or stricturing disease. Conclusions: None of the three main predictive models in paediatric CD achieved sufficient accuracy, far from that reported in the original cohorts.