Special thanks to Cornell Library and their team of Evidence Synthesis librarians for sharing the content used here.
Don't hesitate to contact a UHM Librarian!
According to the Royal Society, 'evidence synthesis' refers to the process of bringing together information from a range of sources and disciplines to inform debates and decisions on specific issues. They generally include a methodical and comprehensive literature synthesis focused on a well-formulated research question. Their aim is to identify and synthesize all of the scholarly research on a particular topic, including both published and unpublished studies. Evidence syntheses are conducted in an unbiased, reproducible way to provide evidence for practice and policy-making, as well as to identify gaps in the research. Evidence syntheses may also include a meta-analysis, a more quantitative process of synthesizing and visualizing data retrieved from various studies.
Evidence syntheses are much more time-intensive than traditional literature reviews and require a multi-person research team. See this PredicTER tool to get a sense of a systematic review timeline (one type of evidence synthesis). Before embarking on an evidence synthesis, it's important to clearly identify your reasons for conducting one. For a list of types of evidence synthesis projects, see the next tab.
One commonly used form of evidence synthesis is a systematic review.
This table compares a traditional literature review with a systematic review.
Traditional Literature Review | Systematic Review | |
---|---|---|
Review Question/Topic | Topics may be broad in scope; the goal of the review may be to place one's own research within the existing body of knowledge, or to gather information that supports a particular viewpoint. | Starts with a well-defined research question to be answered by the review. Reviews are conducted with the aim of finding all existing evidence in an unbiased, transparent, and reproducible way. |
Searching for Studies | Searches may be ad hoc and based on what the author is already familiar with. Searches are not exhaustive or fully comprehensive. | Attempts are made to find all existing published and unpublished literature on the research question. The process is well-documented and reported. |
Study Selection | Often lack clear reasons for why studies were included or excluded from the review. | Reasons for including or excluding studies are explicit and informed by the research question. |
Assessing the Quality of Included Studies | Often do not consider study quality or potential biases in study design. | Systematically assesses risk of bias of individual studies and overall quality of the evidence, including sources of heterogeneity between study results. |
Synthesis of Existing Research | Conclusions are more qualitative and may not be based on study quality. | Bases conclusion on quality of the studies and provide recommendations for practice or to address knowledge gaps. |
See below for resources to help you generate your own PRISMA flow diagram.
The Institute of Medicine recommends that a librarian or information specialist be involved in the systematic review process. In fact, this study published in the Journal of Clinical Epidemiology shows that librarian involvement in systematic reviews improves both the quality and the reproducibility of the literature search.
University of Hawaiʻi at Mānoa Library's SciTech librarians can help you:
Review Methodology Decision Tree (Cornell University Library)
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