A characterization in childhood inflammatory bowel disease, a new population-based inception cohort from South-Eastern Norway, 2005-07, showing increased incidence in Crohn's disease

Objective. Owing to rising incidence rates in inflammatory bowel disease (IBD), there has been increased interest in causal relationships in pediatric disease. The present population-based inception cohort was recruited in the Oslo area from 2005 to 2007, with the aim of conducting a detailed characterization of treatment-naive patients at diagnosis. Material and methods. After an invitation was extended to all general practitioners in the catchment area, patients aged 18 years with suspected IBD were diagnosed by proximal and distal endoscopy, MRI, demographic, clinical, and histological and molecular characteristics. Symptomatic non-IBD patients served as controls. Results. Of 100 pediatric patients, 62 had IBD (39 Crohn's disease (CD), 19 ulcerative colitis (UC), 4 IBD unclassified (IBDU)) and 38 other diseases. Median age at diagnosis for IBD was 13.1 years (56.4% males), median symptom duration 6 months, and 69% L3 (Vienna classification). With 195,000 children aged 18 years in the catchment area, the incidence rate of IBD per 100,000/years inhabitants was 10.9 (6.8 for CD, 3.6 for UC, and 0.6 IBDU) and for those aged 16 years (178,500) the incidence rate was 10.6. The higher NOD2 allele frequency among children may partly contribute to the increase. Conclusions. The results indicate a marked rise in the incidence of CD in contrast to no increase in UC in South-Eastern Norway, compared with the figures from the last 15 years. Time from onset of symptoms to diagnosis still represents a challenge for early characterization in IBD.