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A Synthesis and Evaluation of existing evidence


Welcome to the LibGuide on Reviews - Synthesis and Evaluation of Existing Evidence. This guide is designed to help researchers, students, and practitioners navigate the process of conducting reviews to synthesize and evaluate existing evidence on a particular topic or research question. Reviews play a crucial role in advancing knowledge, informing decision-making, and guiding future research directions in various fields. Whether you are embarking on a systematic review, meta-analysis, scoping review, or another type of review, this guide will provide you with essential resources, tools, and strategies to effectively plan, conduct, and report your review. From defining your research question to synthesizing findings and interpreting results, each step of the review process will be explored in detail.

Learning Objectives:

By the end of this LibGuide, you will be able to:

  1. Understand the different types of reviews and their respective methodologies.
  2. Define a clear research question or objective for your review.
  3. Develop inclusion and exclusion criteria to guide the selection of relevant studies.
  4. Design a comprehensive search strategy to identify relevant literature.
  5. Critically appraise the quality of included studies using appropriate tools or frameworks.
  6. Synthesize findings from individual studies using narrative synthesis, meta-analysis, or other methods.
  7. Interpret the results of your review and identify implications for practice, policy, or further research.
  8. Adhere to established reporting guidelines (e.g., PRISMA) to ensure transparency and completeness in reporting your review.

Throughout this guide, you will find practical tips, examples, and links to resources to support you at each stage of the review process. Whether you are new to conducting reviews or looking to enhance your review skills, this LibGuide will serve as a valuable resource to help you navigate the complex landscape of evidence synthesis and evaluation.

Primary data refers to information that is collected firsthand by the researcher for a specific purpose or study. This can include data gathered through experiments, surveys, interviews, observations, or any other method where the researcher directly interacts with the subjects or sources of data.

Secondary data, on the other hand, refers to information that has already been collected by someone else for a purpose other than the current research study. This can include data from books, journals, databases, government reports, or any other sources where the data was originally collected for a different purpose.

In a systematic review, researchers aim to gather, critically evaluate, and synthesize all available evidence on a particular research question or topic. While both primary and secondary data can be valuable for systematic reviews, secondary data is often more suitable. This is because systematic reviews typically require a large amount of data from multiple studies to draw meaningful conclusions, and secondary data sources offer a wide range of studies that have already been conducted and published.

Using secondary data allows researchers to access a broader pool of information without the need to conduct new studies, which can be time-consuming and expensive. Additionally, secondary data can provide a more comprehensive view of the topic by including studies conducted in different contexts, populations, and time periods.

However, it's essential for researchers conducting systematic reviews to carefully evaluate the quality and relevance of the secondary data they include to ensure the reliability of their findings. They need to assess factors such as the methodological rigor of the original studies, the consistency of findings across studies, and the potential for bias in the data.

Additional Resources:

Cochrane Handbook for Systematic Reviews of Interventions:

PRISMA Flow Diagram: 

PRISMA 2020 flow diagram 

Cochrane Collaboration:

PRISMA checklist

 PRISMA 2020 Checklist (Word)

The checklist can also be completed using a Shiny App available at

An expanded checklist, with references and some examples removed, is also available. 

PRISMA 2020 Expanded Checklist (PDF)

Video for authors using RevMan

Watch a 6-minute YouTube tutorial

Example of forest plot using RevMan for authors


How to cite PRISMA



This LibGuide provides a starting point for your systematic review journey.

Remember, thorough planning, attention to detail, and adherence to established guidelines are key to conducting a successful and impactful review.

Sources for Conducting a Search

  1. Aromataris, E., & Riitano, D. (2014). Constructing a search strategy and searching for evidence. A guide to the literature search for a systematic reviewAmerican Journal of Nursing, 114(5), 49-56.
  2. Kugley, S., Wade, A., Thomas, J., Mahood, Q., Jørgensen, A. M. K., Hammerstrøm, K., & Sathe, N. (2017). Searching for studies: a guide to information retrieval for Campbell systematic reviews. Campbell Systematic Reviews, 13(1), 1–73. doi: 10.4073/cmg.2016.1
  3. Lefebvre, C., Manheimer, E., & Glanville, J. on behalf of the Cochrane Information Retrieval Methods Group (2011). Chapter 6:  Searching for studies. Cochrane Collaboration.

PRISMA Framework:

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) is a checklist and flow diagram that helps ensure transparent and complete reporting of your systematic review. It ensures you report every step of the process, from search strategy to conclusions.

How-to Guide for PRISMA:

  • PRISMA Checklist: Follow the 27-item checklist covering different aspects of your review, from title and abstract to results and discussion.
  • PRISMA Flow Diagram: Use this flow diagram to visually represent the number of studies identified, excluded, and included at each stage of your review process.
  • PRISMA Extensions: PRISMA offers extensions for different types of reviews like scoping reviews and overviews of systematic reviews.

Software for Systematic Reviews:

  • Reference management software: Mendeley, Zotero (Organize references and PDFs)
  • Screening and selection tools: Covidence, Rayyan (Collaboratively screen and select studies)
  • Data extraction tools: EPPI-Reviewer, DistillerSR (Extract data from studies)
  • Risk of bias assessment tools: Cochrane RoB, JBI Critical Appraisal Tools (Assess study quality)
  • Meta-analysis software: RevMan, CMA (Statistically combine study results)
  • This is a beginner's guide, and conducting a systematic review requires training and expertise. Seek guidance from a librarian or research methodologist.
  • Consider utilizing university library resources and workshops on systematic reviews.
  • Be prepared for a time-consuming but rewarding process that contributes valuable evidence-based insights.