INVADE is a successful, evidence-based intervention program for reducing stroke and dementia. Enlisted patients are supervised, monitored and supported at family practices. A web-based application for tablet computers, the INVADE intervention assistant tool (ICAT), has been developed to enhance standardization of intervention delivery and to ensure overall intervention success. ICAT aims at supporting patient consultations, which are a central activity for the intervention conducted by assistant nurses. The application development follows a Design Science approach. Two iterations of problem formulation, development and evaluation have been accomplished. The paper at hand is focused on design and evaluation of the prototype and we reflect evaluation results to conclude on our iterative design approach.