Abstract
Background Over a quarter of adults in Europe have limited health literacy (LHL). LHL hampers their ability to find, understand, and implement medical information, resulting in poorer health outcomes. Shared decision-making (SDM), a process that enhances communication and personalised care and encourages patient involvement, can mitigate the challenges individuals with LHL face. However, healthcare providers often struggle to recognise and effectively engage these patients in SDM. This realist review aims to understand how, why, for whom, and under what circumstances SDM does or does not work for patients with LHL. Methods Realist research provides a framework to understand how and why interventions work in specific contexts by uncovering underlying mechanisms. A realist approach is particularly suited for assessing complex social interventions like SDM. Our realist review, structured in three phases, focuses on developing and refining initial rough programme theories (IRPTs) in the form of context-mechanism-outcome configurations. Phase 1, now complete, involved defining the review scope and developing IRPTs enriched by the feedback of experts in realist-informed research methodologies. Phase 2 will include searching, selecting, and appraising the literature. In phase 3, we will focus on data extraction, analysis, and synthesis to further refine programme theories through stakeholder engagement, including patients with LHL and healthcare providers. Discussion This realist review will provide valuable insights for optimising SDM interventions for patients with LHL, ultimately leading to greater inclusivity and engagement in healthcare and improved health outcomes for this vulnerable group. By elucidating the mechanisms at play, we can tailor these interventions to various contexts, enhancing their effectiveness and generalisability. This protocol presents not only the IRPTs but also provides a detailed description of the methods for the planned realist review. The results of the realist review will inform a subsequent randomised controlled trial and further refine programme theories through a realist evaluation. Systematic review registration PROSPERO CRD42024594762