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Systematic reviews: finding and managing the evidence

This guide gives an overview of how to plan, execute and organize literature searches to support systematic reviews and other projects and research requiring in-depth searches.

Introduction

Documenting your search is a vital part of the research process. Others should be able to evaluate and reproduce your search. At the very least, you should record the following in a systematic review:

  • The databases you have searched and what platform you used (e.g. Medline/Ovid)
  • The dates covered when the search was carried out
  • The line-by-line details of your search strategy and the number of results retrieved
  • Details of other sources searched (e.g. Google Scholar)
  • Your selection criteria and a note of how many articles were excluded

PRISMA Statement

PRISMA - Preferred Reporting Items for Systematic Reviews and Meta-Analyses - aims to help authors improve the reporting of their systematic reviews and meta-analyses. You can read more about PRISMA on the PRISMA Statement website.

PRISMA Checklist
The PRISMA 2020 statement comprises a 27-item checklist addressing the introduction, methods, results, and discussion sections of a systematic review report.

PRISMA-S
The intent of PRISMA-S is to complement the PRISMA Statement and its extensions by providing a checklist that could be used by interdisciplinary authors, editors, and peer reviewers to verify that each component of a search is completely reported and therefore reproducible.

Flow Charts

It is quite typical for studies to use a flow diagram to document their search process. A flow diagram can be used to 'depict the flow of information through the different phases of a systematic review. It maps out the number of records identified, included and excluded, and the reasons for exclusions' (PRISMA, 2019).

The easiest way to start is by recording the databases you have searched and the number of results you retrieved. As you work your way down the flow chart, you should record the number of results you have removed according to your inclusion/exclusion criteria. Simply put, your aim is to explain how you progressed from your search to the papers that you are going to discuss in your review.

Your inclusion/exclusion criteria outline the characteristics that prospective studies must have in order to be included in your systematic review. For example, you may only wish to include articles published after 2015 or studies that have more than x participants. Similarly, you may wish to exclude any study that is not a Randomised Controlled Trial. Speak to your tutor if you are struggling to identify your inclusion/exclusion criteria. 

PRISMA Flow Diagram

PRISMA published the new version of the PRISMA guidelines and flow diagram templates in 2020. There are different versions of the template for different types of research - click on the link to view. PRISMA Flow Diagram. There are also many tools freely available online to help you create your PRISMA Flow Diagram.

NB: PRISMA is just one example of flow charts that document a search strategy. If you search Google for search strategy flow charts you will find many different formats and you are encouraged to find one that works for you.

(left-click on images to view in full resolution)

PRISMA Flow diagram

The PRISMA diagram below can be used if you have also searched for grey literature online, or used additional searching methods such as citation searching.

PRISMA flow diagram