Background
Data of the Dutch longitudinal IBD registries (IBD South Limburg cohort, Parelsnoer IBD cohort, Iniative on Crohn’s disease and Colitis registry) has shown to be valuable by contributing to improved patient stratification and selection of markers to predict treatment outcome. Based on the database models of existing registries, we aim to develop a sustainable and interoperable Real World IBD database model that will contribute to studying the lifelong disease course of IBD over time.

Methods
The design process was iterative and involved the potential end-users of the registries. First the databasemodels of established Dutch IBD cohorts were taken as input, in combination with repeated discussions on the content with three principal IBD investigators.  The second iteration was multifaceted; 1) five focus groups with 7 IBD researchers (MD medicine of which most practiced IBD care) discussing the content, 2) four focus groups with medical students reporting on the practical use and difficulties in data interpretation using the preliminary design of the database model.

Results
The first iteration of the design phase resulted in a database model and ready to use data-entry database, holding 27 independent modules on different themes important for the IBD disease course allowing for repeated data recordings. The second iteration of the design phase resulted in pruning the modules’ content, removal of one module, merging and adding of modules. It was agreed that only data is recorded on events that were reported, to prevent creation of sparse datasets.

Conclusion
An iterative design process for IBD registries involving end-users and a modular database model will result in higher data quality to study the IBD disease course over long time periods. During a third design phase the database model will be evaluated with IBD specialists and the model will be encoded using medical standardized vocabularies (e.g. SNOMED, LOINC).