Evidence Synthesis

This guide serves as a tool for students and researchers who wish to complete an evidence synthesis project. It provides a brief overview of specific steps for conducting evidence syntheses and how the Sprague Library can help. 

Evidence Synthesis is the process of compiling information that identifies, selects, and combines results from multiple studies to answer a research question to help identify gaps in the literature.

Examples of evidence synthesis include systematic reviews, scoping reviews, rapid reviews, meta-analysis, umbrella reviews, and narrative literature reviews.

What to know before beginning an evidence synthesis project:

• Aim is to identify and synthesize all of the scholarly research on a particular topic, including both published and unpublished studies (grey literature).
• It cannot be done alone! Assemble a team to help you complete this project, including a librarian. 
• Determine what type of evidence synthesis project you want to complete (e.g., systematic review vs. meta-analysis). Use this decision tree to determine which review is right for you.
• Evidence synthesis projects take time. Make sure to plan accordingly and coordinate responsibilities with your team.

Systematic review is a comprehensive and exhaustive search of the published and unpublished work surrounding a specific research question. 

• Compares, evaluates, and synthesizes evidence in a search for the effect of an intervention. 
• May take several months to a year to complete. 
• Requires objectivity and a well-defined methodology for others to reproduce as needed.

Scoping review (or Evidence Map) is a preliminary assessment of the current extent and size of available research regarding a more broad research question. 

• Characterizes the quantity and quality of current research.
• Seeks to identify research gaps and opportunities for evidence synthesis rather than searching for the effect of an intervention. 
• May take longer that a systematic review. 

Rapid review uses systematic review methods to identify what is already known regarding a research question under a shortened time frame. 

• Uses methodological short-cuts to limit the standard time it takes to conduct a systematic review.
• Risk for introducing bias and its use should be justified. 
• Useful when in need of a quick turn around. (delete maybe)

Meta-analysis statistically combines the findings from different quantitative studies. 

• Statistical methods are used to objectively evaluate, synthesize, and summarize results.
• Typically analyses the measures of effect.
• May be done as part of a systematic review. 

Umbrella review is systematic review compiling evidence from multiple systematic reviews into an accessible document.

• A systematic review of systematic reviews. 
• Typically uses a broader research question. 
• Addresses the number of evidence syntheses being published on a topic. 

Narrative literature review is a review of published materials that examines recent or current literature on a specific topic.

• Typically of a wider scope.
• Does not require a standardized methodology. 
• Search strategies, comprehensiveness, and time to complete will vary.