Systematic Review of the Literature: A Novel Research Approach
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Systematic Review of the Literature: A Novel Research Approach
Objectives: By the end of the session, the student
will be able to: 1. State the definition of systematic review 2. State the reasons for doing a systematic
review 3. State when a systematic review is needed 4. Know the components of a systematic review 5. Know the process for a systematic review 6. Know how the systematic review process fits
into the 5 chapter dissertation format
What is a Systematic Review? A systematic review is a rigorous and
comprehensive literature review led via a peer-reviewed protocol making it possible to replicate the findings.
“A review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyze the results of the included studies” (Cochrane, 2005, p. 45).
…continued “Systematic reviews attempt to
bring the same level of rigor to reviewing research evidence as should be used in producing that evidence in the first place” (Davies & Crombie, 2009, p. 1).
“The author treats the review as the research process” (source?)
Why Do a Systematic Review? Knowledge explosion makes keeping up with
primary research evidence impossible. Practitioners have wide-ranging information
needs (effectiveness, meaningfulness, feasibility, appropriateness).
Looked at individually, research studies may offer little insight to problems; taken together within a systematic review, a clearer and more consistent picture will emerge.
(Davies & Crombie, 2009)
When is a Systematic Review Needed?
“….systematic reviews are most needed whenever there is a substantive question, several primary studies - perhaps with disparate findings - and substantial uncertainty” (Davies & Crombie, 2009, p.3).
Components of Systematic Review
Identification of all relevant published and unpublished evidence
Selection of studies or reports for inclusion.
Assessment of quality of each study or report
Synthesis of findings from the individual studies or reports in an unbiased way
Synthesis of aggregated findings
The Systematic Review Process: Step 1: Defining the Questions
Define the area of interest and relevant populations.
State clear and appropriate questions. Clearly state the objectives of the
review. Identify the types of evidence or
studies that will help answer the questions.
State intended outcomes.
It has been said that “…the quality of the problem that is formulated is the forerunner of the quality of the solution that will be attained” (Getzels, as cited in Achilles, Reynolds, & Achilles, 1997, p. 31).
In doing a systematic review, it can be said that the quality of the question(s) that is formulated is the forerunner of the quality of the review.
Let’s think about the characteristics of good questions and then look at some examples.
Characteristics of Good Questions
Clear and unambiguous Answerable Relevant Positively worded Free of bias
Shouldn’t hospitals refuse to allow smoking anywhere on their property, sinceeverybody knows thatsmoking causes cancer and heart disease?
Should hospitals refuse to allow smoking anywhere on their property, since everybody knows that smoking causes cancer and heart disease?”
Should hospitals refuse to allow smoking within public view?
Should hospitals offerstop-smoking programs to help citizens stop smoking?
How do changes in smoking policies ofhospitals affect smoking rates?
What group of strategies isassociated with smoking cessation?
The Systematic Review Process: Step 2: Searching the Literature Ideally, all of the published and unpublished
literature should be searched for an unbiased review.
In reality, a designated number of databases are searched using a standardized or customized filter.
“Gray literature” (Davies and Crombie, 2009, p.4) is searched using specialized search engines, databases, and websites.
Expert opinion on where appropriate data may be located is sought.
Key authors are contacted for clarification. (Davies & Crombie, 2009)
Determine whether:
There is sufficient research to accomplish a systematic review
A systematic review is necessary, i.e., there is not already a recent, relevant systematic review
Next…
Access library databases
Select appropriate database(s), given your question(s)
Set limits - e.g. date of publication, human focus, language, abstracts
The Systematic Review Process: Step 3: Assessing the Studies Assess each study for eligibility against
inclusion criteria Retrieve the full text of studies that meet the
inclusion criteria Assess studies for methodological quality
(ideally conducted by two independent reviewers)
Extract findings onto a data extraction form (some studies may be excluded even at this late stage)
Create list of included studies
(Davies & Crombie, 2009)
Screening for Inclusion Screen all references for EACH criterion
you have established. For example:
Empirical IV = smoking cessation strategy DV = smoking rates (smoking cessation rates) Relevant population Published after 2002
In order for references to be included, all criteria must be met.
Retrieving the Papers
Access online journals
Access hard-copy publications
Keep track of references
Assess Quality
Be fair minded. Look for strengths and weaknesses.
Look for internal consistency.
Be thoughtful.
Extract Findings
Look for common themes.
Create list of included studies
The Systematic Review Process: Step 4: Combining the Results
Findings from individual studies must be aggregated. This is called “evidence synthesis” (Davies & Crombie, 2009, p.4)
Type if evidence synthesis is selected to fit the type of data in the review:
a. Meta-synthesis: qualitative data b. Meta-analysis: homogenous quantitative
data c. Narrative summaries: non-homogenous quantitative data
The Systematic Review Process: Step 5: Placing the Findings in Context
Discuss issues such as: Quality and heterogeneity of
studies Likely impact of bias Likely impact of chance Applicability of findings
Systematic Review Proposal
Chapter 1: Introduction (Step 1)
Chapter 2: Literature Search (Describe how Step 2 will be implemented.)
Chapter 3: Methodology (Describe how Step 3 will be implemented.)
Systematic Review Dissertation
Chapter 1: Introduction (Step 1) Chapter 2: Literature Search
(Describe the results of implementing Step 2.)
Chapter 3: Methodology: (Describe the results of implementing Step 3.)
Chapter 4: Results (Step 4) Chapter 5: Discussion (Step 5)
A Word of Caution…
Systematic review is far from easy Requires careful scientific
consideration Requires meticulous and laborious
searching Requires considerable attention to
methodological detail and analysis (Davies & Crombie, 2009, p. 5)
Systematic Review Links
http://www.york.ac.uk/inst/crd/ CRD (Centre for Reviews and Dissemination) is part of
the National Institute for Health Research (NIHR) and is a department of the University of York (United Kingdom). Their website includes databases where you can search for systematic reviews on health and social care.
http://www.thecochranelibrary.com The Cochrane Library provides online access to Cochrane
reviews and also has a "Learn" section with various materials to help you to develop a systematic review.
Systematic Review Links (cont’d) http://eppi.ioe.ac.uk/cms/
The Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre) is part of the Social Science Research Unit at the Institute of Education, University of London. Their website includes databases where you can search for systematic reviews as well as a methods and tools section where you can find data reporting and management tools for use in systematic reviews.
http://www.prisma-statement.org/ PRISMA stands for Preferred Reporting Items for
Systematic Reviews and Meta-Analyses. It is an evidence-based checklist of items for inclusion in systematic reviews and meta-analyses.
A Final Word
This has been an overview. Should you decide to pursue a
systematic review of the literature for your dissertation, you will need to work closely with your chair to select/develop appropriate protocol and data extraction forms.