‘How Well Do We Mix?’ A Scoping Review of Mixed Methods Review Methodologies

Background:Mixed methods reviews are increasingly used to address complex healthcare and social research questions; however, their methodological diversity has led to fragmentation in terminology, design, and execution. This lack of clarity presents challenges for both methodological choice and reproducibility.Aim:To systematically map and critically examine the range of mixed methods review approaches, with a focus on their methodological characteristics, integration processes, and operational guidance.Methods:A scoping review was conducted to identify methodological papers and applied examples of mixed methods reviews. To be included, studies had to primarily identify instructional content on how to undertake a mixed methods review, including information on integration or synthesis of data. Data were extracted on review type, synthesis processes, integration mechanisms, data transformation, and use of frameworks or guidance tools. Findings were analysed using an extraction map which provided the basis for synthesis of information.Results:Ninety-two methodological contributions were identified. A wide range of review types were identified, including realist, meta-narrative, mixed methods systematic, integrative, framework, rapid, scoping and QCA-informed approaches. Mixed methods systematic reviews and framework synthesis approaches were the most identified approaches. Despite this diversity, four dominant integration mechanisms emerged: narrative, comparative, mapping-based, and mixed-evidence integration. Operational clarity varied substantially, with theory-driven and structured approaches (e.g., realist synthesis, QCA) demonstrating clearer procedural guidance than integrative and rapid approaches. Iterative processes and theoretical engagement were key differentiators between descriptive and explanatory review outputs.Conclusion:Mixed methods review approaches are characterised by both methodological richness and conceptual fragmentation. Greater emphasis is needed on standardising reporting, clarifying integration and transformation processes, and aligning methodological choices with review purpose. This review provides a structured framework to support methodological decision-making and enhance transparency in mixed methods evidence synthesis.