At the article screening stage reviewers remove studies that are not related to the research topic. Your inclusion/exclusion criteria will be used to determine this. It is recommended that at least two independent reviewers participate in the screening process, both of whom being subject experts. Where disagreements arise during the screening process, a third party should be introduced to resolve any conflicts.
The first screening will be of the title and abstracts of articles found. Next, the full text articles should be screened to ensure that those studies suit the eligibility criteria for the systematic review being carried out.
There are many free or subscription-based resources that you can use to streamline the screening/data extraction phases of your systematic review. We have an institutional subscription to Covidence and it is the tool we recommend you to use.
Data extraction is the process of capturing key details from your eligible studies in a structured, standardised format and organising that information in a way that will enable you to build your evidence table, evaluate the risk of bias in individual studies, and synthesise their findings.
In this step you will systematically organise relevant information that you have “extracted” from eligible studies, such as study title, authors, year, methods, and conclusions, following established guidelines like PRISMA. The information to be extracted will depend on the goals of the review.
Tools like Covidence/RevMan assist with data extraction, though some researchers use Excel for its simplicity. During this stage, you'll create evidence and summary tables to summarise findings and assess studies for quantitative synthesis.
What is Covidence?
Covidence is a web-based software platform that streamlines the production of systematic reviews. It supports reference/citation screening, full-text review, risk of bias assessment, extraction of study characteristics and outcomes, and the export of data and references.
Using Covidence
DCU has an institutional subscription to Covidence making it freely available to DCU users. For more information on signing-up to Covidence and starting a review see our dedicated Institutional Covidence page.
DCU access entitles you to unlimited reviews with unlimited references, citations, and reviewers for each review.
The Covidence Knowledge Base has information on everything from setting up your review to exporting your data at the end. It includes helpful webinars, videos, and articles that take you through every step of the process.
What is PRISMA?
The PRISMA reporting guidelines are designed to help authors report why their systematic review was done, what methods they used, and what they found.
The main PRISMA reporting guideline (the PRISMA 2020 statement) provides guidance for the reporting of systematic reviews evaluating the effects of interventions.
The Statement consists of a 27 item checklist (which details the sections which must be reported) and a flow diagram (depicting the the flow of studies through the different stages of the review).
PRISMA 2020 is complemented by various PRISMA extensions, which provide guidance for the reporting of different aspects or types of reviews (e.g. search, protocol, scoping reviews).
Note: Covidence automatically populates the PRISMA flowchart - see picture on the right - as you work through the steps of the review.
See below an example of a PRISMA flow chart from a systematic review on a similar topic.
(Honeycutt et al., 2022)
Honeycutt, L. et al. (2022) 'A systematic review of the effects of e-cigarette use on lung function', NPJ Primary Care Respiratory Medicine, 32, article number 45. Available at: https://doi.org/10.1038/s41533-022-00311-w