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Evidence Synthesis: Types of Synthesis

Guidance through the process for Evidence Synthesis.

Methods

A research method is the procedure or technique applied to gather and critique data which is related to a research question (surveys or interviews are some examples of a method). This includes matching the research question to the appropriate type of synthesis (review types), selecting a framework to define inclusion/ exclusion criteria and developing the protocol.

This page will introduce you to different methods to understand the importance of knowing which will be most suited to your synthesis type.

Types of synthesis

Synthesis Type Purpose Methodologies Sources
Integrative Review /Narrative Review 

Develop question for policy/practice

Identify gaps in literature

Integrate qualitative/quantitative data

Whittemore and Knaff’s (2005) 5-stage integrative review method

Critical Appraisal Skills Checklist (CASP) for appraisal of studies.

Braun and Clark (2022) thematic analysis.

Popay et al (2006) Guidance and conduct of narrative synthesis in systematic reviews.

DatabasesGrey literature citation and reference checking.
Systematic Review

Determine state of existing knowledge

Used for developing guidelines, policies, best practice

Make proposals for future research

Cochrane Handbook for Systematic Review of Interventions

Methodological Expectations of Cochrane Intervention Reviews (MECIR)

Preferred reporting items for systematic reviews and meta - analyses (PRISMA) statement

DatabasesGrey literature citation and reference checking, trial registers
Scoping Review

Identify knowledge gaps

Set agendas for research

Determine implications for decision making

JBI Evidence Synthesis Manual

Johanna Briggs Institute (JBI) Data extraction

PRISMA extension for Scoping Reviews (PRISMA – ScR)
DatabasesGrey literature citation and reference checking.
Qualitative Evidence Synthesis (QES)

Review complex research questions

Collate qualitative research to enable new understandings of data to emerge

Meta-ethnography approach - reviewing and synthesizing findings of qualitative research.

Critical Appraisal Skills Checklist (CASP) for qualitative studies.

Preferred reporting items for systematic reviews and meta - analyses (PRISMA) statement.

eMERGe reporting guidelines.
DatabasesGrey literature citation and reference checking.

 

Systematic Review versus a Systematic Literature Review!

The traditional literature review is designed to increase knowledge of and provide a broader overview of a topic area. They can take a systematic (consistent and planned) approach depending on how thorough the review needs to be. Increasingly review/synthesis types are adopting a more systematic process.

A systematic review is a high-level overview of a focused research question using rigorous and reproducible methodologies to systematically search, critically appraise and synthesize the evidence. This review type requires an extensive time frame (12-18 months) and involves a team.

Further reading:

Sutton, A, Clowes M, Preston L, Booth A (2019) 'Meeting the review family: exploring review types and associated information retrieval requirements', Health Information Libraries Journal, 36 (3), pp. 202-222.

Grant, M.J., Booth A (2009) ‘A typology of reviews: an analysis of 14 review types and associated methodologies’, Health Information Libraries Journal, 26 (2), pp. 94-95.

Right Review (knowledgetranslation.net) - free tool to help with selecting the best review type.

Siddaway, A. P., et al. (2019). "How to Do a Systematic Review: A Best Practice Guide for Conducting and Reporting Narrative Reviews, Meta-Analyses, and Meta-Syntheses." Annual Review of Psychology 70(1): 747-770.

Frameworks

There are many frameworks such as PEO, PICO, SPIDER, which can help to develop your research area and form your research question by:

  • Breaking down the research area into various concepts
  • Using these concepts to form search strategies
  • Identifying the key concept for the research question
  • Defining inclusion and exclusion criteria 

Note: The research question may not fit to a framework, what is important is that all the descriptors for concepts and terms have been captured through rigorous searching.

Develop a research - question - LibGuides at Duke University Medical Center

Munn, Z., Stern, C., Aromataris, E. et al. What kind of systematic review should I conduct? A proposed typology and guidance for systematic reviewers in the medical and health sciences. BMC Med Res Methodol 18, 5 (2018). https://doi.org/10.1186/s12874-017-0468-4.

Selecting synthesis (review) type

Right Review - Knowledge Translation Program.

Which Type of Review is Right For You? (Cornell University Library).

Sage Research Methods

Project Planner Tool /Philosophy of research /

What’s the Difference Between Methodology and Methods? / What’s the Difference Between Qualitative and Quantitative Methods?

Research Design / Which methods should I use?

Protocols

A protocol is a road map for your research which will help to define your question and plan your methodology.

Registering a protocol is usually required for most synthesis types.

Always check first before you begin to make sure that similar research hasn't already been done or could be currently in progress. This your piece of research.

Why is a protocol important?

  1. Sets a framework for the review
  2. Helps planning, scheduling, establishing boundaries
  3. Minimize risk of bias
  4. Access to peer review (Cochrane protocols are peer reviewed)
  5. Less duplication of work
  6. Endorses transparency of methods

Developing the protocol: PRISMA-P

Registering your protocol:

Campbell Collaboration produces systematic reviews and other evidence-based synthesis in areas such as crime, justice, education, social welfare and international development.

Cochrane Library of Systematic Reviews and Trials. Search the Cochrane Library to see if there are any protocols or reviews similar to your topic of interest before you develop and register a new review.

Epistemonikos - a collaborative multi-lingual database of health evidence. It is the largest source of systematic reviews, relevant for health-decision making, and a large source of other types of scientific evidence. (Epistemonikos website, April 2021).

Open Science Framework - an open-source project management tool which helps researchers through the research life cycle.

PROSPERO is the international prospective register for Systematic Review Protocols.

The Joanna Briggs Institute (JBI) evidence based practice database contains over 3,000 records across seven publication types including Best Practice Information Sheets, Systematic Review Protocols and Systematic Reviews.