Evidence Synthesis & Literature Reviews

colorful gears on a table

Librarians are available to assist at different stages in the evidence synthesis process. Learn more about levels of librarian collaboration.

Who We Are

Our librarians have co-authored hundreds of evidence synthesis articles. Librarians and library staff are continually trained on new search methodologies and processes. We adhere to the requirements for authorship and contributor-ship of the International Committee of Medical Journal Editors (ICMJE).

Who You Are

To ensure alignment with institutional goals, evidence synthesis consultations are available to teams where BOTH the lead researcher/primary contact (first author) and group leader/PI (last author) are current faculty, staff, or students whose primary affiliation is at YSM, YSPH, YSN, or YNHH.

Learn more…

Self-Guided Help & Training

Evidence Synthesis Process

Below are the steps required to complete a rigorous evidence synthesis. View this process as a graphic

  1. Build your evidence synthesis team
  2. Review reporting guidelines, best practice handbooks, and training modules
  3. Formulate question and decide on review type
  4. Search for previous published literature and protocols
  5. Develop and register a protocol
  6. Develop and test search strategies
  7. Peer review of search strategies
  8. Execute search
  9. De-duplicate results
  1. Screen title and abstracts
  2. Retrieve full-text articles
  3. Screen articles in full-text
  4. Search for grey literature
  5. Quality assessment and data extraction
  6. Citation chasing
  7. Update database searches
  8. Synthesize data
  9. Manuscript development

Review Types

what type of review could you write flowchart

Flowchart Title: “What type of Review Could You Write”

  • Top of chart begins Q: “How big is your team?”
  • If “Open”, then “Scoping Review”
  • If “Just me” to team size, then Q: “Do you want a robust methodology?”
  • If “Yes” to robust methodology, then “Rapid Review”
  • If “No to robust methodology, then “Narrative Review”
  • If team size is “More than one”, then Q: “Is your research question close-ended or open-ended?”
  • If “Closed”, then “Systematic Review”
  • If “Systematic Review”, then Q: “Will you analyze results quantitatively?”
  • If “Yes”, then “Systematic Review and Meta-analysis”
Descriptions of Review Types
Reproduced from: Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J. 2009 Jun;26(2):91-108. doi: 10.1111/j.1471-1842.2009.00848.x. Review. PubMed PMID: 19490148.
LabelSearchAppraisalSynthesisAnalysis
Critical review
Aims to demonstrate writer has extensively researched literature and critically evaluated its quality. Goes beyond mere description to include degree of analysis and conceptual innovation. Typically results in hypothesis or model. 		Seeks to identify significant items in the field.No formal quality assessment. Attempts to evaluate according to contribution.Typically narrative, perhaps conceptual or chronological.Significant component: seeks to identify conceptual contribution to embody existing or derive new theory.
Literature review
Generic term: published materials that provide examination of recent or current literature. Can cover wide range of subjects at various levels of completeness and comprehensiveness. May include research findings. 		May or may not include comprehensive searching.May or may not include quality assessment.Typically narrative.Analysis may be chronological, conceptual, thematic, etc.
Mapping review/systematic map
Map out and categorize existing literature from which to commission further reviews and/or primary research by identifying gaps in research literature. 		Completeness of searching determined by time/scope constraints.No formal quality assessment.May be graphical and tabular.Characterizes quantity and quality of literature, perhaps by study design and other key features. May identify need for primary or secondary research.
Meta-analysis
Technique thatstatistically combines the results of quantitative studies to provide a more precise effect of the results. 		Aims for exhaustive searching. May use funnel plot to assess completeness.Quality assessment may determine inclusion/exclusion and/or sensitivity analyses.Graphical and tabular with narrative commentary.Numerical analysis of measures of effect assuming absence of heterogeneity.
Mixed studies review/mixed methods review
Refers to any combination of methods where one significant component is a literature review (usually systematic). Within a review context it refers to a combination of review approaches for example combining quantitative with qualitative research or outcome with process studies. 		Requires either very sensitive search to retrieve all studies or separately conceived quantitative and qualitative strategies.Requires either a generic appraisal instrument or separate appraisal processes with corresponding checklists.Typically both components will be presented as narrative and in tables. May also employ graphical means of integrating quantitative and qualitative studies.Analysis may characterize both literatures and look for correlations between characteristics or use gap analysis to identify aspects absent in one literature but missing in the other.
Overview
Generic term: summary of the [medical] literature that attempts to survey the literature and describe its characteristics. 		May or may not include comprehensive searching (depends whether systematic overview or not).May or may not include quality assessment (depends whether systematic overview or not).Synthesis depends on whether systematic or not. Typically narrative but may include tabular features.Analysis may be chronological, conceptual, thematic, etc.
Qualitative systematic review/qualitative evidence synthesis
Method for integrating or comparing the findings from qualitative studies. It looks for ‘themes’ or ‘constructs’ that lie in or across individual qualitative studies. 		May employ selective or purposive sampling.Quality assessment typically used to mediate messages not for inclusion/exclusion.Qualitative, narrative synthesis.Thematic analysis, may include conceptual models.
Rapid review
Assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research. 		Completeness of searching determined by time constraints.Time-limited formal quality assessment.Typically narrative and tabular.Quantities of literature and overall quality/direction of effect of literature.
Scoping review
Preliminary assessment of potential size and scope of available research literature. Aims to identify nature and extent of research evidence (usually including ongoing research). 		Completeness of searching determined by time/scope constraints. May include research in progress.No formal quality assessment.Typically tabular with some narrative commentary.Characterizes quantity and quality of literature, perhaps by study design and other key features. Attempts to specify a viable review.
State-of-the-art review
Tend to address more current matters in contrast to other combined retrospective and current approaches. May offer new perspectives on issue or point out area for further research.		Aims for comprehensive searching of current literature.No formal quality assessment.Typically narrative, may have tabular accompaniment.Current state of knowledge and priorities for future investigation and research.
Systematic review
Seeks to systematically search for, appraise and synthesis research evidence, often adhering to guidelines on the conduct of a review.		Aims for exhaustive, comprehensive searching.Quality assessment may determine inclusion/exclusion.Typically narrative with tabular accompaniment.What is known; recommendations for practice. What remains unknown; uncertainty around findings, recommendations for future research.
Systematic search and review
Combines strengths of critical review with a comprehensive search process. Typically addresses broad questions to produce ‘best evidence synthesis’. 		Aims for exhaustive, comprehensive searching.May or may not include quality assessment.Minimal narrative, tabular summary of studies.What is known; recommendations for practice. Limitations.
Systematized review
Attempt to include elements of systematic review process while stopping short of systematic review. Typically conducted as postgraduate student assignment. 		May or may not include comprehensive searching.May or may not include quality assessment.Typically narrative with tabular accompaniment.What is known; uncertainty around findings; limitations of methodology.
Umbrella review
Specifically refers to review compiling evidence from multiple reviews into one accessible and usable document. Focuses on broad condition or problem for which there are competing interventions and highlights reviews that address these interventions and their results. 		Identification of component reviews, but no search for primary studies.Quality assessment of studies within component reviews and/or of reviews themselves.Graphical and tabular with narrative commentary.What is known; recommendations for practice. What remains unknown; recommendations for future research.

Getting Started

Medical Library Systematic Searches Tutorials – this series covers the fundamental concepts and general procedure of searching the health science literature to ensure your search is comprehensive, methodical, transparent and reproducible.

Campbell Collaboration – video recordings that explain Campbell methods, for both beginners in evidence synthesis or experienced systematic reviewers.

Covidence Academy – learn key concepts for conducting systematic reviews, such as search strategies and data extraction.

All Medical Library training – check out training and events offered by the medical library.

Consultations & Collaborations

Comprehensive searches are time-intensive and each librarian can work on a limited number of reviews. Librarian participation may be delayed or unavailable if we are at capacity.

Scope of Assistance for Evidence Synthesis & Literature Review Projects

Librarians can collaborate with you to determine how we are best able to support an evidence synthesis research project.

Librarian Roles

  • Translate research question into appropriate search strategy framework [PICO; PEO; PCC; SPIDER]
  • Assist with search strategy
  • Guidance on bibliographic organization tools
  • Guidance with selecting relevant reporting guidelines/standards
  • Manuscript and protocol preparation (coauthored projects only)
    • Provide search methods writeup
    • Develop search history appendix
    • Review full manuscript

Library Staff Support (coauthored projects only)

  • Retrieve full-text articles
  • Covidence review initiation

Levels of Librarian Collaboration

Researcher Self-Guided

Librarian role:

  • Provide researcher teams with resources for conducting evidence synthesis projects

Lead author/primary contact can expect to:

  • Access resources for self-guided evidence synthesis development
Librarian Consultation

Librarian role:

  • Meet with the lead researcher/primary contact (first author) and group leader/PI (last author) (BOTH must be current faculty, staff, or student whose primary affiliation is at YSM, YSPH, YSN, or YNHH)
  • Peer review comprehensive search developed by researcher

Lead author/primary contact can expect to:

  • Provide librarian with completed search for peer review and ‘Search Methods’ section in the evidence synthesis protocol
Librarian Collaboration

Librarian collaboration satisfies ICJME criteria for coauthorship. Coauthorship is expected when the librarian is a collaborator on all evidence-synthesis projects.

Note: Student evidence synthesis projects and Yale-led Professional Society evidence synthesis projects will be reviewed on a case-by-case basis.

Librarian role:

  • Meet with the lead researcher/primary contact (first author) and group leader/PI (last author) (BOTH must be current faculty, staff, or student whose primary affiliation is at YSM, YSPH, YSN, or YNHH)
  • Develop search and iterations in consultation with research team
  • Deduplicate search results and upload into screening tool
  • Assist with obtaining full-text articles
  • Write the search methods section for the protocol and final manuscript
  • Provide information for manuscript acknowledgement noting support from library staff
  • Review manuscript prior to submissions

Lead author/primary contact can expect to:

  • Include manuscript acknowledgement noting support from library staff
  • Sign Memorandum of Understanding before librarian work commences
  • Include the librarian as a coauthor on the protocol, final manuscript, and all research outputs resulting from this project (e.g. posters and conference papers)
  • Provide librarian with detailed research protocol
  • Provide at least four gold standard articles – articles that would be included in the review

To request a systematic review or evidence synthesis project, please fill out this form.

To request a general search, please fill out this form.

Tools, Guidelines, Protocols

Tools

Search Strategies

Methodology Guidelines

Reporting Guidelines

Quality Assessment & Risk of Bias Instruments

Protocol Templates

Protocol Registries

 Articles

Books

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