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What is a systematic review?

A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993). 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.

Many systematic reviews contain meta-analyses. Meta-analysis is the use of statistical methods to summarize the results of independent studies (Glass 1976). By combining information from all relevant studies, meta-analyses can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review (see Chapter 9, Section 9.1.3). They also facilitate investigations of the consistency of evidence across studies, and the exploration of differences across studies.

Citation: Cochrane Handbook for Systematic Reviews of Interventions, Section 1.2.2

What is the difference between a Systematic Review and a Literature Review?



Systematic Review


Literature Review


 Focused on a single question.

 Not necessarily focused on a single question but may describe an  overview.


 A peer-reviewed protocol or plan is included.

 No protocol is included.


 Both provide summaries of the available literature on a topic


 Clear objectives are identified.

 Objectives may or may not be identified.

 Inclusion & exclusion  criteria

 Criteria stated before review is conducted.

 Criteria not specified.

 Search strategy

 Comprehensive search conducted in a systematic way.

 Strategy not explicitly stated.

 Process of selecting  articles

 Usually clear and explicit.

 Usually not described.

 Results and data  synthesis

 Clear summaries based on high quality evidence.

 Summary based on studies where the quality of articles may not be  specified.

 May also be influenced by the reviewer’s theories, needs and beliefs.


 Written by an expert or group of experts with a detailed and well-grounded knowledge of the issues.

Adapted from: the University of Newcastle Library

Process of information retrieval for systematic reviews and health technology assessments on clinical effectiveness - European network for Health Technology Assessment (EUnetHTA) - December 2017 
Systematic reviews take time to do well (link to a portion of the book by Booth et al). 
Systematic approaches to a successful literature review / Andrew Booth, Diana Papaioannou, Anthea Sutton. Thousand Oaks, CA : Sage Publications, c2012.

How can we help?

Research librarians can partner on systematic reviews.

Add us to your team (acknowledgement as contributors) and we will design and manage complex, thorough searches in multiple databases and provide results in an EndNote Library.

Searching to support the production of a systematic review is complex and time consuming - it takes days to weeks depending on the topic.

Librarians will provide you with search strategies and results as required by the 2009 PRISMA Statement for Reporting Systematic Reviews and Meta-Analyses of Studies That Evaluate Health Care Interventions: Explanation and Elaboration.