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Advanced literature search and systematic reviews

An introduction to systematic reviews

Analyse and understand your results

Once you have performed your literature search to find studies covering your research question the next stage is to analyse and interpret them. This involves: 

  • selecting the studies from those you have found which you would like to include in your review 
  • assessing the quality of every study you are including 
  • extracting and synthesising the findings (data) from all the studies in an unbiased way.  

Screen your results

The first step in analysing your results should be to test them against your inclusion and exclusion criteria from your protocol. Any results to be included in your review should be those that meet all your inclusion criteria. 

There are three stages in the screening process: 

  1. Pre-screening: Record the number of results from your search before screening commences. Use reference management software to remove any duplicate results you have retrieved. 

  2. Title/Abstract screening: Go through the titles and abstracts of your results, removing any records which clearly do not meet your inclusion criteria. Don't be too strict in defining what meets your criteria at this stage as titles and abstracts offer only limited information. 

  3. Full text screening: Get the full text of all studies which you have left. These should then be screened closely to see if they meet your criteria. You should keep a record of any studies you have excluded as you may need to give some details about these in the methodology section of a thesis and results section of a systematic review.

Assess the quality of your results

Once you know which studies meet your criteria you need to appraise them for quality. Part of this quality check is checking for the risk of bias amongst studies you have found. 

Below are a list of checklists and guides which can help with this.  

Assessing quality guides Scope
CASP (Critical Appraisal Skills Programme) checklists Designed for use with systematic reviews, randomised controlled trials, cohort studies, case control studies, economic evaluations, diagnostic studies, qualitative studies and clinical prediction rule. 
CEBM (Centre for Evidence-Based Medicine) critical appraisal tools Provides worksheets covering systematic reviews, randomised controlled trials, qualitative studies, diagnostic studies and prognosis studies. 
JBI (Joanna Briggs Institute) critical appraisal tools Checklists designed for use with systematic reviews, randomised controlled trials, cohort studies, case control studies, case reports, case series, economic evaluations, diagnostic studies, qualitative research, cross sectional, prevalence and quasi-experimental studies.
AACODS checklist for appraising grey literature  Designed to enable evaluation and critical appraisal of grey literature. 

Data analysis

You now need to decide what sort of data analysis you want to do with the results you are left with. It will be either quantitative (a meta-analysis) using some statistical tools or qualitative (a narrative analysis) using a written assessment.  

You may want to use a Data Extraction Form to help you. The Cochrane Collaboration has created a template that can be edited to suit your requirements:

Software for systematic reviews

There is a range of software packages that can help you with the screening and data analysis process.  

Please note that the Library does not support or provide training for any of these resources. 

Software Description 
Covidence Can be used for screening and to support data extraction. Free trial for a limited amount of records is available, then requires annual subscription. A Covidence help guide is available.
DistillerSR Subscription based software, designed for the screening and data extraction. 
Eppi-Reviewer An application for all types of literature review, including systematic reviews, meta-analysis and 'narrative' reviews. The School of Health and Psychological Sciences has a subscription that students and researchers can use. Check the Eppi-Reviewer instructional videos
Rayyan  Freely available software that can be used for the screening process. 
RevMan Freely available software from the Cochrane Collaboration. 
Systematic review toolbox Community-driven, searchable, web-based catalogue of tools that support the systematic review process. Aims to help reviewers find appropriate tools based on their needs. 

Other software that could help you when you are analysing your research:

  • NVivo - a programme used for qualitative and mixed-methods research. Specifically, it is used for the analysis of unstructured text, audio, video, and image data, including interviews, focus groups, surveys, social media and journal articles. 
  • SPSS (Statistical package for social sciences) - used to perform statistical analysis. 

The Library does not provide training in the use of this software, but it is available to City students.