["Donnainformata-mammografia": a decision aid developed and validated in the Italian setting]. / Donnainformata-mammografia: un decision aid costruito e validato nel setting italiano.

The decision aid "Donnainformata-mammografia" (https://www.donnainformata-mammografia.it/en/) has been developed with the aim of providing clear information on the benefits and harms of breast cancer screening, and the controversies on the relationship between mortality reduction and overdiagnosis. It was evaluated in a randomized clinical trial showing it increases informed choice and does not decrease participation in screening.This article describes the framework, the guiding principles, and the operational phases of the tool development.The project was developed within the national screening programme. The promoters decided to state their placement, to start from the information needs of women and what is already known, and to balance spontaneous navigation with "nudging" to key contents. Three focus groups with 18 women and 4 interviews were organized. Participants expressed a favourable attitude towards screening, and no knowledge of the debate on screening efficacy and overdiagnosis. A literature review and a comparison of decision aids were conducted. The online tool included the results of these steps. The home page presents key information with links to relevant topics, so that the person can decide to stop there having an overview or to continue. The «ready to decide¼ button, which leads to the section of decision support, can be clicked on every page. Here, the person can evaluate a list of key points on the basis of her values, in order to decide to participate in screening or not.