Background: Our aim was to estimate the completeness-that is, whether all patients were included in the system-and the validity-that is, whether the diagnostic criteria were fulfilled for the patients registered-of the diagnoses of Crohn's disease and ulcerative colitis in a Danish hospital system.
Methods: Information in a regional hospital system, in the County of North Jutland, Denmark, was compared with hospital records and information in a pathology system.
Results: The analysis of the completeness included 143 patients with Crohn's disease and 285 patients with ulcerative colitis. The completeness of the regional hospital system using the pathology system as a reference standard was 94% for both diseases. The analysis of the validity included 281 patients registered as having Crohn's disease and 506 patients registered as having ulcerative colitis. The validity of the two diagnoses was 97% and 90%, respectively.
Conclusions: The regional hospital system showed few misclassifications of the diagnoses of Crohn's disease and ulcerative colitis. Thus the nationwide hospital system (based on the regional hospital systems) may provide a unique study base for future research.