LibGuides: Evidence Synthesis : Systematic Reviews

Evidence Synthesis and Systematic Reviews

"'Evidence synthesis' refers to the process of bringing together information from a range of sources and disciplines to inform debates and decisions on specific issues. Decision-making and public debate are best served if policymakers have access to the best current evidence on an issue." Systematic Reviews and published protocols are types of evidence synthesis that can be conducted for this and many other purposes.

This guide is designed to help the user choose the type of review, protocol, reporting and evidence gathering that will fulfill their research question. We recommend contacting one of the librarians at the earliest stage for assistance with any evidence sythesis project.

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(Royal Society 2018, https://royalsociety.org/topics-policy/projects/evidence-synthesis)

Systematic Reviews

According to the Cochrane Handbook, section 1.2.2, "a systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question."

The key characteristics of a systematic review are:

a clearly stated set of objectives with pre-defined eligibility criteria for studies;
an explicit, reproducible methodology;
a systematic search that attempts to identify all studies that would meet the eligibility criteria;
an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

Source: Green, S., Higgins, J.P.T., Alderson, P., Clarke, M., Mulrow, C.D., Oxman, A.D. (2008). Chapter 1: Introduction. In: Higgins, J.P.T., Green, S. (Eds.), Cochrane handbook for systematic reviews of interventions. The Cochrane Collaboration.

Timeline

A systematic review is a lengthy process. Here is a general timeline for conducting a systematic review:

Month	Activity
1-2	Preparation of protocol
3-8	Searches for published and unpublished studies
2-3	Pilot test of eligibility criteria
3-8	Inclusion assessments
3	Pilot test of 'Risk of bias' assessment
3-10	Validity assessments
3	Pilot test of data collection
3-10	Data collection
3-10	Data entry
5-11	Follow up of missing information
8-10	Analysis
1-11	Preparation of review report
12-	Keeping the review up to date

Source: Green, S. and Higgins, J.P. (2008). Preparing a cochrane review. In J.P. Higgins and S. Green (eds.), Cochrane handbook for systematic reviews of interventions. https://doi.org/10.1002/9780470712184.ch2