Evaluation of a downstaging, bidirectional version of the Montreal classification of Crohn's disease: Analysis of 5‐year follow‐up data from the prospective BioCrohn study

Summary Objective Under the assumption of irreversibility, the Montreal classification provides a unidirectional assessment of the complications and behaviour of Crohn's disease (CD) that does not allow for downstaging. We examined the use of a bidirectional Montreal classification system that can capture disease regression. Design From the BioCrohn Registry, an inception cohort of patients with CD for ≤12 months duration was defined and followed up for 5‐years. Cumulative probabilities for developing complications were estimated using the Kaplan–Meier method. Potential associations of explanatory variables with disease progression were estimated with Cox regression. Results Among 393 incident CD patients (of whom 255 completed the entire follow‐up), the 5‐year cumulative probability of developing complications was 41.5% (15.6% and 25.9% for stricturing and penetrating complications respectively). Perianal disease (hazard ratio [95% confidence interval]: 8.45 [4.74–15.07]) and surgical resection of the intestine (2.71 [1.50–4.92]) in the very early phase of the disease were associated with a higher risk of developing a penetrating complication within the 5‐year follow‐up. The use of a bidirectional Montreal classification system which can account for disease regression demonstrated that 90% of patients exhibited inflammatory disease behaviour at 5 years, in contrast to 58%, if the hierarchical, unidirectional Montreal classification system was used. Conclusion An additional bidirectional disease behaviour assessment capturing reversed or fully controlled complications may provide a more realistic appraisal of the complexity and unmet needs of patients treated with advanced therapies. Use of a bidirectional Montreal classification system only for disease behavior that are to be found at the time of assessment showed that 90% of patients suffered from a purely inflammatory disease at 5‐ years, in contrast to 58%, if the hierarchical, unidirectional Montreal classification system was used.