Systematic & Scoping Review Guide

Knowledge Synthesis refers to a wide array of review methods that involve: 

• an explicit aim
• development of a methodological protocol
• comprehensive search strategies to find relevant research articles
• a method or tradition of evaluating quality and potential risk of bias in individual studies
• explicit data collection and synthesis procedures (Whittemore et.al., 2014)

Knowledge Synthesis methods include such reviews as systematic reviews, umbrella reviews, scoping reviews, rapid reviews, etc. and this guide will focus on systematic and scoping reviews.

Definitions:

• Systematic Review
• Scoping Review
• Literature Review

Grant, M. J., & Booth, A. (2009). A typology of reviews: An analysis of 14 review types and associated methodologies. Health Information and Libraries Journal, 26(2), 91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.x

Dalmer, N. K. (2020). Unsettling Knowledge Synthesis Methods Using Institutional Ethnography: Reflections on the Scoping Review as a Critical Knowledge Synthesis Tool. Qualitative Health Research, 30(14), 2361–2373. https://doi.org/https://dx.doi.org/10.1177/1049732320949167

Neilson, C. J. (2021). Adoption of peer review of literature search strategies in knowledge synthesis from 2009 to 2018: An overview. Health Information and Libraries Journal, 38(3), 160–171. https://doi.org/https://dx.doi.org/10.1111/hir.12367

Sarkis-Onofre, R., & Agostini, B. A. (2020). Knowledge synthesis: How to improve the use of evidence from clinical trials?. International Journal of Paediatric Dentistry, 31 Suppl 1, 66–74. https://doi.org/https://dx.doi.org/10.1111/ipd.12744

Garritty, C., Stevens, A., Hamel, C., Golfam, M., Hutton, B., & Wolfe, D. (2019). Knowledge Synthesis in Evidence-Based Medicine. Seminars in Nuclear Medicine, 49(2), 136–144. https://doi.org/https://dx.doi.org/10.1053/j.semnuclmed.2018.11.006

Whittemore, R., Chao, A., Jang, M., Minges, K. E., & Park, C. (2014). Methods for knowledge synthesis: An overview. Heart & Lung, 43(5), 453–461. https://doi.org/https://doi.org/10.1016/j.hrtlng.2014.05.014

Systematic review refers to the process of systematically bringing together the results of any research using rigorous predefined methodology.  It uses explicit reproducible methods to identify and critically appraise and combine results of primary research studies.

• Key stages of a systematic review are
  • Develop a predefined, structured and searchable research question
  • Clarify aims and methods in a protocol (often peer-reviewed and published) 
    • objectives are clearly stated
    • inclusion/exclusion criteria are clearly stated
  • Identify relevant sources of information (multiple databases to be exhaustive)
  • Develop a search strategy to retrieve all available relevant research 
  • Collect data
  • Assess quality - validity of findings in the studies of interest
  • Synthesize evidence with an effort to avoid biases
  • Present findings
    • PRISMA or equivalent
    • tables presenting data from included articles
  • Interpret findings

When done well, this provides reliable findings from which conclusions can be drawn and decisions made (clinical, policy, etc.)

This short video from Cochrane provides a brief overview of what systematic reviews are.

Pollock A, Berge E. How to do a systematic review. Int J Stroke. 2018 Feb;13(2):138-156.

Shamseer L, Moher D, Clarke M, Ghersi D, Liberati A, Petticrew M, Shekelle P, Stewart LA; PRISMA-P Group. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015: elaboration and explanation. BMJ. 2015 Jan 2;350:g7647.

Petticrew M. Systematic reviews from astronomy to zoology: myths and misconceptions. BMJ. 2001 Jan 13;322(7278):98-101. Review.

Scoping Review is a literature synthesis method that maps key concepts that underpin a particular research area and clarifies working definitions. It establishes conceptual boundaries of a topic and reveals evidence gaps. Scoping reviews do not necessarily focus on a specific research methodology but rather "scope" the literature for what has been published on a topic.

• Key stages of a scoping review are: 
  • Develop a structured and searchable research question
  • Clarify aims and methods in a protocol (often peer-reviewed and published)
    • objectives are clearly stated
    • range of evidence is uncovered (qualitative and quantitative) 
    • direction is provided for ensuing primary research or systematic review
  • Identify relevant sources of information (multiple databases to be exhaustive)
  • Develop a search strategy to retrieve all available relevant research - this can be iterative depending on findings
  • Find all existing evidence regardless of quality (no critical appraisal) 
  • Chart the results with descriptive summaries that align with the research question 
  • Present results as a map or description of available evidence 
  • Present findings
    • PRISMA or equivalent
    • tables presenting data from included articles
  • Interpret findings

Arksey, H., & O’Malley, L. (2005). Scoping studies: Towards a methodological framework. International Journal of Social Research Methodology: Theory and Practice, 8(1), 19–32. https://doi.org/10.1080/1364557032000119616

Gottlieb, M., Haas, M. R. C., Daniel, M., & Chan, T. M. (2021). The scoping review: A flexible, inclusive, and iterative approach to knowledge synthesis. AEM Education and Training, 5(3), e10609. https://doi.org/https://dx.doi.org/10.1002/aet2.10609

Lockwood, C., Dos Santos, K. B., & Pap, R. (2019). Practical Guidance for Knowledge Synthesis: Scoping Review Methods. Asian Nursing Research, 13(5), 287–294. https://doi.org/https://dx.doi.org/10.1016/j.anr.2019.11.002

For more on how to conduct a scoping review, see the JBI Manual for Evidence Synthesis, Chapter 11: Scoping Reviews

Literature review refers to secondary literature whose purpose is to introduce context and current thinking about a topic and so may cover several aspects of that topic. A literature review is a survey of literature on a given research topic that seeks to identify existing literature to support a thesis statement. It is not a simple list of studies on a given topic but studies are assessed and synthesized based on the researcher's topic of research. Gaps in the literature can be identified from conducting a literature review and can be a justification for conducting further research. When conducting a literature review, a research methodology of a study is not the primary focus, however, any themes emerging from the review are identified. A majority of research papers, regardless of methodology almost always contain a literature review. 

• Key aspects of a literature review are:
  • All stages of a literature review can be iterative
  • References are located serendipidously without a strategy being explicitly stated or reproducible
  • It summarizes some of the available literature without being comprehensive or exhaustive
    • Usually no more than 1 or 2 databases are searched
    • The search strategy is not translated into the syntax of other databases if they are used
  • Critical appraisal is not applied
  • Data is presented in narrative and/or diagrammatic form (PRISMA is not used)
  • Results are interpreted by the writer and may be influenced by their theories, beliefs and needs