Knowledge synthesis methods for integrating qualitative and quantitative data: a scoping review reveals poor operationalization of the methodological steps

Abstract Objectives To describe and compare, through a scoping review, emerging knowledge synthesis methods for integrating qualitative and quantitative evidence in health care, in terms of expertise required, similarities, differences, strengths, limitations, and steps involved in using the methods. Study Design and Setting Electronic databases (e.g., MEDLINE) were searched, and two reviewers independently selected studies and abstracted data for qualitative analysis. Results In total, 121 articles reporting seven knowledge synthesis methods (critical interpretive synthesis, integrative review, meta-narrative review, meta-summary, mixed studies review, narrative synthesis, and realist review) were included after screening of 17,962 citations and 1,010 full-text articles. Common similarities among methods related to the entire synthesis process, while common differences related to the research question and eligibility criteria. The most common strength was a comprehensive synthesis providing rich contextual data, whereas the most common weakness was a highly subjective method that was not reproducible. For critical interpretive synthesis, meta-narrative review, meta-summary, and narrative synthesis, guidance was not provided for some steps of the review process. Conclusion Some of the knowledge synthesis methods provided guidance on all steps, whereas other methods were missing guidance on the synthesis process. Further work is needed to clarify these emerging knowledge synthesis methods.