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Systematic Reviews

What is systematic review?

A systematic review attempts to collate all the 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 et al 1992, Oxman and Guyatt 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.

Green, S., Higgins, J.P.T., Alderson, P., Clarke, M., Mulrow, C.D., Oxman, A.D. (2008). Chapter 1: Introduction. In J.P.T. Higgins, & S. Green (Eds.), Cochrane Handbook for Systematic Reviews of Interventions: Cochrane Book Series (pp. 1-9). The Cochrane Collaboration. 

Systematic reviews vs. literature review

 

Systematic review

Literature review

Question

Focused on a single  question. 

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

Protocol

 A peer review protocol or plan is included.

No protocol is included.

Background

Both provide summaries of the available literature on a topic

Objectives

Clear objectives are identified.

Objectives may or may not be identified.

Inclusion and exclusion criteria

Criteria stated before the 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.

Not described in a literature review.

Process of evaluating articles

Comprehensive evaluation of study quality.

Evaluation of study quality may or may not be included.

Process of extracting relevant information

Usually clear and specific.

The process of extracting relevant information is not explicit and clear.

Results and data synthesis

Clear summaries of studies 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.

Discussion

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

Reproduced from: Bettany-Saltikov, J. (2010). Learning how to undertake a systematic review: part 1. Nurs Stand, 24(50), 47-55; quiz 56. https://doi.org/10.7748/ns2010.08.24.50.47.c7939