Maarten Cozijnsen

144 It is hypothesized that achieving histological (microscopic) remission may have additional value over endoscopic (macroscopic) CD remission alone. 27 In theory, the less signs of inflammation, the deeper the disease remission, the longer the duration until a relapse of inflammation. This theory might turn out to be true for CD, but remains to be demonstrated. A first step would be to demonstrate association between histological CD activity scores and clinical outcome. This could be tested on patients included in the TISKids trial, as mucosal biopsies were taken at baseline and – in a subgroup of the patients – again at week 10 and 52. However, several difficulties can be expected. Firstly, the accuracy of mucosal biopsies to detect full histologic remission might be low without any detectable macroscopically evident inflammation to guide biopsy taking, and given the patchiness of CD inflammation and the small part of the mucosal surface that can be assessed by taking biopsies. Secondly, only a portion of patients will achieve endoscopic remission and an even smaller portion both histologic and endoscopic remission. This can limit the statistical power when making the comparison.