In this thesis, we aimed to develop and validate a patient and a physician questionnaire to measure the shared decision making (SDM) process in oncology. We identified SDM measurement challenges:... Show moreIn this thesis, we aimed to develop and validate a patient and a physician questionnaire to measure the shared decision making (SDM) process in oncology. We identified SDM measurement challenges: there is limited evidence on measurement properties, patients’ role is not assessed while it is present in SDM models, patients and healthcare professionals have been involved only to a limited extent in the development of SDM measurement instruments, and a reflective measurement model is often assumed, while a formative might be more appropriate. The aim of this thesis was therefore to develop and validate questionnaires to assess the SDM process in oncology from both the patient and the physician viewpoints. We chose the oncology setting because it is a setting in which patients often face preference-sensitive decisions, and in which most patients prefer an active or collaborative role in treatment decision making. To inform the development and validation process of our questionnaires, we used the original Consensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist and we wrote two reviews: one on existing SDM measurement instruments and one on existing SDM models. The iSHARE questionnaires shows adequate measurement properties Show less