Which instruments are used to measure shared, supported and assisted healthcare decision-making between patients who have limited, impaired or fluctuating capacity, their family carers and healthcare professionals? A systematic review protocol.

Background: Shared decision-making (SDM) is a dialogical relationship where the physician and the patient define the problem, discuss the available options according to the patient's values and preferences, and co-construct the treatment plan. Undertaking SDM in a clinical setting with patients who have limited, impaired or fluctuating cognitive capacity may prove challenging. Supported (defined "Assisted" in the Irish context) decision-making describes how people with impaired or fluctuating capacity remain in control of their healthcare-related choices through mechanisms which build and maximise capacity. Supported and assisted decision-making (ADM) within healthcare settings is theoretically and practically novel. Therefore, there is a knowledge gap about the validity of psychometric instruments used to assess ADM and its components within clinical settings. This systematic review aims to identify and characterise instruments currently used to assess shared, supported and assisted healthcare decision-making between patients with limited, impaired or fluctuating capacity, their family carers and healthcare professionals. Methods: A systematic review and narrative synthesis will be performed using a search strategy involving the following databases (PubMed, Cinahl, Embase, Web of Science, Scopus and PsycINFO). Quantitative studies published in the last decade and describing psychometric instruments measuring SDM, supported decision-making and ADM with people having limited or fluctuating capacity will be considered eligible for inclusion. Title and abstract screening will be followed by full-text eligibility screening, data extraction, synthesis and analysis. This review will be structured and reported according to the PRISMA checklist. The COSMIN Risk of bias checklist will be used to assess the quality of the instruments. Discussion: The results will inform and be useful to HCPs and policymakers interested in having updated knowledge of the available instruments to assess SDM, supported and assisted healthcare decision-making between patients who have impaired or fluctuating capacity, their family carers and healthcare professionals. Registration: PROSPERO CRD42018105360; registered on 10/08/2018.