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For Researchers

What is a systematic review?

A systematic review is a summary of literature that uses explicit methods to perform a comprehensive literature search and critical appraisal of individual studies and that uses appropriate statistical techniques to combine these valid studies. (CEBM).

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
  • a systematic presentation, and synthesis, of the characteristics and findings of the included studies. (Cochrane Handbook for Systematic Reviews of Interventions, 2008, p. 6)

Meta analysis is a systematic review that uses quantitative methods to synthesize and summarize the results.

Locating systematic reviews

Campbell Collaboration
Cochrane Library (Wiley)
Includes all Cochrane Reviews (and protocols) prepared by Cochrane Review Groups. Each Cochrane Review is a peer-reviewed systematic review that has been prepared and supervised by a Cochrane Review Group according to the Cochrane Handbook for Systematic Reviews of Interventions or Cochrane Handbook for Diagnostic Test Accuracy Reviews.
 
Systematic reviews and guidelines for environmental management.
 
DARE: Database of Reviews of Effects
Database of promoting health effectiveness reviews (DoPHER)
EPPI: The Evidence for Policy and Practice Information and Co-ordinating Centre
Joanna Briggs Institute (Ovid)

Australia map

JBI is an international collaboration involving nursing, medical and allied health researchers, clinicians, academics and quality managers across 40 countries in every continent.
 
OT Seeker (Occupational Therapy Evidence)
PsycBITE
speechBITE

Searching systematically

Searching is a critical part of conducting the systematic review, as errors in the search process potentially result in a biased or otherwise incomplete evidence base. Searches for systematic reviews need to be constructed to maximise recall and deal effectively with a number of potentially biasing factors. (McGowan, 2005, p. 75)

You should aim to be as extensive as possible when conducting searches for systematic reviews. However, it may be necessary to strike a balance between the sensitivity and precision of your search.

Sensitivity – the number of relevant results identified divided by the total number of relevant results in existence
Precision - the number of relevant results identified divided by the total number of results identified.
 
Increasing the comprehensiveness of a search will reduce its precision and will retrieve more non-relevant results.

However,
... at a conservatively-estimated reading rate of two abstracts per minute, the results of a   database search can be ‘scanread’ at the rate of 120 per hour (or approximately 1000  over an 8-hour   period), so the high yield and low precision associated with systematic review searching is not as   daunting as it might at first appear in comparison with the total  time to be invested in the review. (Cochrane Handbook for Systematic Reviews of Interventions, 2011, Chapter 6.4.4)

A useful technqiue is to check the search strategies used in other systematic reviews for hints on terms and combinations to use. Several groups have also developed pre-tested search filters.

Highly recommended chapter:  Booth, A., Papaioannou, D., & Sutton, A. (2012). Ch. 5: Searching the literature IN Systematic approaches to a successful literature review (pp. 71-96). London: SAGE Publications.

Types of reporting bias include:

  • Publication bias
  • Time lag bias
  • Multiple (duplicate) publication bias
  • Location bias
  • Citation bias
  • Language bias
  • Outcome reporting bias

For details see: Cochrane Handbook for Systematic Reviews of Interventions (2008, Chapter 10)

The following sites include examples of pre-tested search filters:

Centre for Evidence-Based Medicine - Formulating Answerable Clinical Questions

CIAP NSW Clinical Learning Module Asking a Clinical Question

Similiarities and differences between systematic and literature reviews

Reproduced from: Bettany-Saltikov, J. (2010). Learning how to undertake a systematic review: Part 1. Nursing Standard, 24(40): p. 47-55.

 

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

Not clear or explicit

Results and Data Synthesis

Clear summaries of studies based on high quality evidence

Summary based on studies where the quality of the 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

 

 

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