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Systematic Review

Screening

Screening is a quality assessment process that selects studies from search results for eligibility.

  • Screening is usually done by two (or more) reviewers independently to avoid bias. Disagreements between reviewers should be resolved by consensus, or by the decision of a third reviewer
  • The inclusion/exclusion criteria are applied to this process
  • Consult the checklists/guidelines for assessing the quality of studies and critical appraisal

Screening steps

  • Remove duplicates from the search results
  • Screen titles and abstracts using the inclusion/exclusion criteria
  • Remove studies that don't meet the inclusion criteria
  • Locate full text of those studies remaining after the first screening 
  • Screen the full-text using the inclusion/exclusion criteria and finalise the studies that are eligible for the review 

Minimise bias

Record screening results

  • Record the studies that were excluded and included. Annotate with the reason as to why they were excluded (eg. did not meet inclusion criteria A, and/or met exclusion criteria B)
  • PRISMA flow diagram is a good template for recording the screening results 
  • PRISMA flow diagram generator could be useful 

Tools

There are software programs that can assist the screening process. Referencing software and Excel files can also be used for recording this process. Find more information from the Systematic Review Tools page.

Niederstadt, C., & Droste, S. (2010). Reporting and presenting information retrieval processes: The need for optimizing common practice in health technology assessment. International Journal of Technology Assessment in Health Care, 26(4), 450-457. https://doi.org/10.1017/S0266462310001066

Schlosser, R. W., Wendt, O., & Sigafoos, J. (2007). Not all systematic reviews are created equal: Considerations for appraisal. Evidence-Based Communication Assessment and Intervention, 1(3), 138-150. https://doi.org/10.1080/17489530701560831 

Extract data

The next step after the screening process is data extraction from the selected studies. This is usually done by a group of collaborators. 

The Cochrane Guide Chapter 5: Collecting Data provides useful information on the data extraction process.

  • Elements of each study, such as methods, participants, setting, interventions, outcome, results, and publications, etc. will be noted down into a data extraction form. 
  • Excel spreadsheet may be sufficient for recording a small or straightforward study with a small number of collaborators.
  • Systematic review software could be used for a larger and more complex study with several collaborators. 

Tools

Synthesise data

Qualitative synthesis and meta-analysis are important methods for data synthesis.

Qualitative synthesis

There are various methods that can be used for synthesising qualitative research. The following readings may give you some ideas: 

  • Barnett-Page, E., & Thomas, J. (2009) Methods for the synthesis of qualitative research: a critical review. BMC medical research methodology, 9, Article 59. https://biomedcentral.com/1471-2288/9/59
  • Booth, A., Papaioannou, D., & Sutton, A. (2012). Systematic approaches to a successful literature review. Sage.
  • Paterson, B. L., Thorne, S. E., Canam, C., & Jillings, C. (2001). Meta-study of qualitative health research. Sage. https://doi.org/10.4135/9781412985017
  • Wong, G., Greenhalgh, T., Westhorp, G., Buckingham, J., & Pawson, R. (2013). RAMESES publication standards: Realist syntheses. BMC Medicine, 11, Article 11. https://doi.org/10.1186/1741-7015-11-21

Meta-analysis

A statistical method for analysing the differences of the selected studies and their effects. Read the Cochrone handbook, chapter 10 Analysing data and following articles for more information. 

  • Lee, C.H., Cook, S., Lee, J.S., & Han, B. (2016). Comparison of two meta-analysis methods: Inverse-variance-weighted average and weighted sum of z-score. Genomics & Informatics, 14(4), 173–180. https://doi.org/10.5808/GI.2016.14.4.173and undertaking meta-analysis 
  • Neyeloff, J. L., Fuchs, S. C., & Moreira, L. B. (2012). Meta-analyses and Forest plots using a microsoft excel spreadsheet: Step-by-step guide focusing on descriptive data analysis. BMC Research Notes. 5, Article 52. https://doi.org/10.1186/1756-0500-5-52
  • Sena, E. S., Currie, G. L., McCann, S. K., Macleod, M. R., & Howells, D. W. (2014). Systematic reviews and meta-analysis of preclinical studies: Why perform them and how to appraise them critically. Journal of Cerebral Blood Flow and Metabolism, 34(5), 737–742. https://doi.org/10.1038/jcbfm.2014.28 
  • Tawfik, G. M., Dila, K. A. S., Mohamed, M. Y. F., Tam, D. N. H., Kien, N. D., Ahmed, A. M., & Huy, N. T. (2019). A step by step guide for conducting a systematic review and meta-analysis with simulation data. Tropical Medicine Health, 47, Article 46. https://doi.org/10.1186/s41182-019-0165-6
  • How to interpret a forest plot (Youtube video by Terry Shaneyfelt)

Data synthesis tools

There are data synthesis tools available to assist analysing selected studies.