Enhancing Public Health Systematic Reviews With Diagram Visualization

Systematic reviews provide a critical summary of a body of knowledge that links research to decision making, whether to inform public health, clinical medicine, medical education, system-level changes, or advocacy. Good reviews are accessed by a wide range of audiences, including health service users, health service providers, and policy decision makers. Because the topics studied, the thinking behind the review questions, the analytical plan, and the review’s interpretation in the broader policy context are often complex, diagrams can play an important role in communicating the review to the reader. Indeed, graphic design is increasingly important for researchers to communicate their work to each other and the wider world.1 Visualizing the topic under study facilitates discussion, helps understanding by making complexity more accessible, provokes deeper thinking, and makes concepts more memorable.2 Higher impact scientific articles tend to include more diagrams, possibly because diagrams improve clarity and thereby lead to more citations or because high-impact articles tend to include novel, complex ideas that require visual explanation.3

Merriam-Webster’s Dictionary defines a diagram as “a graphic design that explains rather than represents, especially: a drawing that shows arrangement and relations (as of parts).”4 Established standards exist for visualizing the flow of studies through a review,5 risk of bias, and individual study and meta-analysis results in forest plots; these are not the subject of this editorial. We consider diagrams that communicate the conceptual framework underpinning reviews.

Diagrams include “logic models,” “framework models,” or “conceptual models”—terms that are often used interchangeably and inconsistently in the literature.6 We examine how diagrams can help review authors and readers and offer guidance for presenting information diagrammatically. We based our work on a purposive search for diagrams from the Cochrane Library and sources of reviews more likely to illustrate conceptual frameworks. Drawing on the data and our own experience, we adapted rapid appraisal methods7 for analyzing documents, taking an iterative, inductive approach to understand what enhances the clarity and utility of diagrams. We then related this learning to methodological articles of systematic reviewing and science communication (Appendix A, available as a supplement to the online version of this article at http://www.ajph.org). We built on our collective experience of diagrams in reviews and helping others to develop them.

We first describe diagrams’ various purposes. Then we discuss what we recognized, as systematic review readers, authors, and editors, as important steps to creating a good diagram. Next, we consider how diagrams can enhance the review process for authors. We discuss these findings in relation to methodologies that routinely integrate diagrams into structure systematic reviews: framework synthesis8 and logic models of illness or treatment pathways, where principles and agreed good practice are emerging.9 Finally, we discuss theories underpinning science communication.10