Data on diabetes will also be used to explore and better understand the Breakthrough model as an implementation method. Only uncontrolled observational studies have, so far, described the outcomes of Breakthrough collaboratives. They also describe significant differences between teams in specific improvements made in patient care and organisational performance, resulting in different implementation and medical costs. There is hardly any information regarding these costs and the cost-effectiveness of collaboratives, and little knowledge about how they could be made more effective. Insight is also needed into the factors that influence the success of individual teams. There are no data regarding the sustainability of improvements.