Gibson D. Lewis Library Libguides
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Evidence synthesis is a collective term that encompasses research that synthesizes existing studies using rigorous methodology and reporting guidelines to provide comprehensive answers to research questions. The Evidence Synthesis International (ESI) Position statement defines evidence synthesis as the following: “Evidence synthesis uses formal, explicit, and rigorous methods to bring together the findings of research already completed, to provide an account of the totality of what is known from that pre-existing research.”
A systematic review is a well-recognized type of evidence synthesis but there are many other evidence synthesis methods to consider when approaching a research project. These include meta-analysis, scoping reviews, rapid reviews, umbrella reviews, and narrative reviews. The review types all vary in terms of scope, comprehensiveness, time commitment, size of team, and purpose. For more information about different review types, please visit the Review Type section.
Systematic reviews are considered one of the highest forms of evidence in the Evidence-Based Pyramid, offering a thorough and detailed synthesis of existing research. This type of study systematically collects, evaluates, and integrates relevant data on a specific topic or research question. By highlighting trends, identifying gaps in the literature, and offering well-supported conclusions, systematic reviews play a crucial role in shaping practice guidelines and policy decisions. They provide a clear, unbiased, and transparent summary of research findings, conducted using a structured and rigorous methodology.
At the bottom of the pyramid are animal and laboratory studies. While they provide valuable information, they are the lowest quality of evidence because their findings may not apply to humans. Moving up, case series and case reports focus on individual patients or small groups. Next, cross-sectional studies offer a snapshot of data at a single point in time, without proving cause and effect. Case-control studies compare individuals with a specific condition to those without it, identifying potential risk factors. Next, cohort studies track groups over time to see how exposures affect health. Above that are randomized controlled trials (RCTs), which randomly assign treatments and are among the most reliable forms of evidence. Finally, at the top are meta-analyses and systematic reviews, which combine results from multiple studies to provide comprehensive insights.