Overview of evidence synthesis types and modes

Background and Objectives

Evidence syntheses systematically compile and analyze information from multiple sources to support health-care decision-making. As many different types of questions need to be answered in health care, different evidence synthesis types have emerged. In this article, we introduce the most common types of evidence synthesis.

Study Design and Setting

We discuss the aims, key methodological features, and illustrative examples of different evidence synthesis types and modes, drawing on our work with the Evidence Synthesis Taxonomy Initiative (ESTI).

Results

Evidence synthesis types include systematic reviews, qualitative evidence syntheses, mixed methods reviews, overviews of reviews, and ‘big picture reviews’ (scoping reviews, mapping reviews, and evidence gap maps). Additionally, we focus on rapid and living reviews as modes and how they can be applied to different evidence synthesis types.

Conclusion

It is essential to understand the main types of evidence synthesis to choose the most suitable method for addressing a specific health-related question.

Plain Language Summary

Health-care decisions should be based on the best available evidence. To bring together findings from many studies, researchers use evidence synthesis-structured methods that summarize what is known on a topic. Because health questions differ, various types of evidence syntheses exist, each designed for specific needs. This article explains the aims and characteristics of the most common types of evidence synthesis: systematic reviews, overviews of reviews, qualitative evidence syntheses, mixed methods reviews, and ‘big picture reviews’ (scoping reviews, mapping reviews, and evidence gap maps). We also describe two ways evidence syntheses can be carried out: rapid reviews (done quickly to support urgent decisions) and living reviews (regularly updated as new evidence becomes available). Understanding the different approaches helps clinicians, patients, and policymakers select the right type of review for their health questions. This ensures that decisions are guided by evidence that is both reliable and appropriate for the situation.