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Systematic Reviews

What is a Systematic Review?

A systematic review consists on combining the results of several studies to answer a research question and not only what has been written on a theme, as is the case of the literature review. In Social Sciences, more often, one seeks to evaluate the effectiveness of an intervention.

Systematic reviews use systematic and explicit methods to identify, select and critically appraise relevant research and to collect and analyse data from the studies included on the review (Glossary of Cochrane). Thus, in order to minimise bias and make reviews reproducible, pre-specified research questions and methods that are documented in protocols are used. Statistical methods (meta-analysis) may or may not be used to analyse and summarise the results of the included studies.

Why Do a Systematic Review?

Systematic reviews are used to:

  • confirm appropriateness of current practice, programs or policies as it answers questions about what works and what does not
  • resolve conflicting evidence when the results of several studies are contradictory
  • highlight need for future research: systematic reviews map areas of uncertainty and identify where little or no relevant research has been done, but where new studies are needed

Steps in a Systematic Review

  • Formulation of a research question
  • Documentary research
  • Registration of the protocol
  • Processing the studies (data):
    • Citation management
    • Article screening
    • Quality assessment
    • Data extraction
    • Synthesise, map or describe the results

Differences Between a Systematic Review and a Literature Review

It is common for students or researchers to confuse systematic reviews with literature reviews; however, before beginning the process, it is very important to know the differences between the two because systematic reviews require more time and resources.

Main differences between Systematic Reviews and Literature Review
  Systematic Review Litterature Review
Definition High-level of primary research on a focused question that identifies, selects, synthesises and appraises all high quality research evidence relevant to that question Qualitatively summarises evidence on a topic using informal or subjective methods to collect and interpret studies
Goals Answers a focused question. Eliminate bias Provides summary or overview of topic

Clearly defined and answerable question

Recommends using PICO as a guide

Can be a general topic or a specific question

Pre-specified eligibility criteria

Systematic search strategy

Assessment of the validity of findings

Interpretation and presentation of results

Reference list





Reference list

Number of Authors Three or more One or more
Timeline Months to years. Average of eighteen months Weeks to months

Thorough knowledge of topic

Performs searches of all relevant databases

Statistical analysis resources (for meta-analysis)

Understanding of topic

Performs searches of one or more databases

Value Supports evidence-based practice Provides summary of literature on a topic

Based on Kysh, Lynn (2013). Difference between a systematic review and a literature review.