To avoid bias, systematic reviews must comprehensively search for all relevant published and unpublished research. An effective search strategy considers all possible terms, searches various databases and other resources, and documents the process. The search aims to be highly sensitive to find all relevant studies while being specific enough to exclude irrelevant ones later. Guidance from Cochrane and CRD can help with developing search strategies and conducting thorough systematic reviews.

1. Literature searching for
systematic reviews
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/

2. Systematic reviews
• “A systematic review attempts to
identify, appraise and synthesize all the
empirical evidence that meets pre-
specified eligibility criteria to answer a
given research question” (Cochrane
Library)
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
Cochrane Library (2013). About Cochrane Systematic Reviews and Protocols [online]. Available at:
http://www.thecochranelibrary.com/view/0/AboutCochraneSystematicReviews.html [accessed 19/7/2013].

3. Publication bias
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
To avoid publication bias the search must
pick up on:
• All published research:
• In major peer reviewed journals
• In lesser known publications
• Any non-published research
• Non-English language materials

4. Finding Published research
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
Searching for published research is the easy bit …
• Major bibliographic databases e.g. Medline and
Embase
• Specialised databases e.g. PsycINFO for
psychology and psychiatry
• Trials registers
• Hand checking reference lists of relevant articles
• Citation searching – searching for articles that
have cited relevant papers

5. Finding unpublished research
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
Finding unpublished research is not so easy, but
there are some good places to start
• Trials registers – to identify trials currently in
progress
• Conference proceedings
• Dissertations
• Contacting authors / experts
• Searching the websites or repositories of
professional societies, relevant organisations
and academic institutions

6. Resources
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
The University of York Centre for Reviews
and Dissemination provide a guide to
useful resources for systematic review
searches
http://www.york.ac.uk/inst/crd/pdf/Findin
g_studies_for_systematic_reviews.pdf

7. Search strategies
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
• The search needs to be highly sensitive
to ensure nothing is missed
• It’s better to be too broad and exclude
studies later than miss out on something
relevant
• The search strategy needs to be
documented

8. Search strategies
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
• Use PICO to break down your search
strategy into concepts:
• Patient / population
• Intervention
• Comparison
• Outcome
• You don’t need to use all parts of the
PICO if it might restrict your search

9. Search strategies
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
• Identify all possible terms
• Think about synonyms, abbreviations,
acronyms, spelling variants
• Use both free text searching and controlled
vocabularies (e.g. MeSH)
• Look at how relevant papers have been
indexed to identify terms
• Look at search strategies of relevant papers
to identify keywords

10. Search strategies
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
• Use operators to combine your searches:
• OR to combine related terms, synonyms etc.
• AND to combine all your concepts together
• ADJ or NEAR for terms in close proximity
• Search filters can be used in some
databases to identify particular types of
study e.g. randomised controlled trials
www.york.ac.uk/inst/crd/intertasc/

11. Summary
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
When carrying out a literature search for a
systematic review you must:
• Search all relevant databases and other
resources
• Find unpublished material
• Consider all possible terminology
• Ensure that your search is broad,
systematic and comprehensive

12. Further reading
RDF
InformationLiteracy
http://www.library.qmul.ac.uk/
Both Cochrane and the CRD at York produce
comprehensive guides to conducting
systematic reviews
• http://www.york.ac.uk/inst/crd/SysRev/!S
SL!/WebHelp/SysRev3.htm
• http://handbook.cochrane.org/