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This is a guide to standalone evidence synthesis projects, such as systematic reviews, scoping reviews, and guideline updates.
If you are reviewing the literature to...
...you may benefit from the information and resources in this guide. However, the process we present here is for writing review articles and may be more structured and/or time-intensive than is appropriate for your objectives.
According to the CDC, a systematic review requires at a minimum:
If the review includes a meta-analysis (quantitative synthesis), a statistician is also required.
Systematic reviews and other syntheses of pre-appraised, filtered information are often depicted as the top tiers of the pyramid of evidence (below); they are considered the gold standard in evidence-based medicine and healthcare decision-making.
These advanced evidence-synthesis projects follow rigorous methodologies to identify, analyze, appraise, and synthesize all relevant data on a focused research question or topic while minimizing bias. They adhere to high reporting standards to ensure that the conclusions drawn are based on the best available evidence and that the reviewers methods are transparent and replicable.
In many ways, evidence syntheses are more akin to original research—using published study reports as research subjects rather than humans or animals—than to review articles. Primary studies are included or excluded according to pre-defined criteria, data are gathered and analyzed using consistent methods, and investigators go to great lengths to minimize and account for bias of various kinds.
These projects offer valuable insights for clinicians, researchers, policymakers, and other stakeholders in making informed decisions and formulating evidence-based guidelines and practices.
Narrative reviews are more subjective, often relying on expert option and knowledge of the literature to provide a summary of published studies without standardized data collection, synthesis, or appraisal methods. Both types of reviews have their place in the academic literature, with evidence synthesis projects offering a more robust foundation for evidence-based decision-making. Notice that narrative reviews are close to the bottom of the evidence pyramid.
Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) is an evidence-based standard for reporting systematic reviews in articles for publication. Despite the use of the word “preferred,” the PRISMA checklist represents the minimum content of a systematic review report.
PRISMA is primarily concerned with systematic reviews and meta-analyses of randomized controlled trials. However, it is increasingly used to synthesize other forms of research. To facilitate this expansion further, extensions to the PRISMA standard have been published for the following purposes.
These standards provide more detailed guidance on reporting specific parts of a systematic review.
These standards offer guidance on reporting other kinds of synthesis.
These standards are for reviews of study types other than RCTs.
Cochrane reviews are generally considered the gold standard of systematic reviews and meta-analyses. To be included in the Cochrane Database of Systematic Reviews, evidence syntheses must meet a higher standard even than those of PRISMA.