Systematic Reviews
Effective Literature Searching
Brenda Thomas
Information Specialist
Cochrane Stroke Group
Stroke Review Group
Comprehensive and versatile register of
randomised controlled trials (RCTs) and
controlled clinical trials (CCTs)
Prepare, keep up to date and disseminate high
quality systematic reviews in all aspects of
stroke healthcare
Role of the
Trials Search Co-ordinator (TSC)/
Information Specialist
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Deliver a comprehensive trials identification strategy
Assess and code relevant stroke trials
Develop and maintain quality and growth of the
register of randomised trials and controlled clinical
trials
Support review authors
Contribute to the review editorial process
Considerable time and resources have been committed
to maximising trial identification
Specialised Register of
Stroke Trials
As many potentially relevant Randomised Controlled
Trials (RCTs) and Controlled Clinical Trials (CCTs) as
possible
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Published trials in any language from any
year
Unpublished trials
Ongoing trials
Planned trials
All the available evidence
The Cochrane Stroke Group
Trials Register
How we identified 13000
stroke trial reports
Stroke Group Trials Register is one of the most advanced
in the Collaboration
All published trial reports included in
the Cochrane Central Register of Controlled Trials in
The Cochrane Library
Methods
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Identify sources of relevant trials
Develop appropriate search
strategies
Screen bibliographic details for
potential reports of trials
Obtain full copies and apply selection
criteria
Arrange translation if required
A systematic approach to
trial identification
• Electronic databases
• Handsearching
• Personal communication
Multiple overlapping search strategies
to minimise bias
Supported by the considerable resources of
The University of Edinburgh and NHS Scotland e-library
Electronic resources
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Major medical bibliographic databases
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Eg MEDLINE and EMBASE
Topic specific databases
Non-English language databases
International trials and research registers
(ongoing trials)
The Internet
Regular searches of 27 bibliographic databases
Approx 25,000 references screened annually
Topic Specific Databases
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BIOSIS Previews (Biology and pharmacology)
AMED (Allied and Complementary Medicine)
CINAHL (Nursing and Allied Health)
PsycINFO (Psychology)
Digital Dissertations (Theses)
MANTIS (Manual, alternative and natural therapy)
International Pharmaceutical Abstracts
Occupational Therapy Journal of Research Index
Applied Social Sciences Index and Abstracts
Clinical Trials Registers
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bibliographic
Cochrane Central Register of Controlled Trials
(CENTRAL) (The Cochrane Library)
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The most comprehensive source of reports of controlled trials
Chinese Clinical Trials Register
The Physiotherapy Evidence Database (PEDro)
Database of Randomised Controlled Trials in
Hyperbaric Medicine (DORCTHIM)
ongoing
Stroke Trials Directory http://www.strokecenter.org/trials/
Current Controlled Trials http://www.controlled-trials.com/
GlaxoSmithKline Clinical Trials Register
RehabTrials.org
Electronic journals
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Contents pages and abstracts on-line
Current awareness alerts
Selected free articles or issues
Full text (free or subscribed)
Download pdfs
Personal Communication and
The Internet
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Trialists and colleagues
Drug Companies
Equipment manufacturers
Websites: e.g. company press releases, research centre
bulletins, research funders
News alerts eg MEDSCAPE
http://www.medscape.com/neurology
News media (current awareness)
Conference abstracts on-line
Essential sources of unpublished and ongoing trials
Reference lists
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Trial reports from publications not indexed
in bibliographic databases
Early trial reports
References from grey literature
Conference abstracts
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books
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theses
Review-specific searches
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Electronic searches
Geographic, eg Chinese Biomedical Literature
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Subject specific, Engineering databases
Handsearching
specialist journals and conference proceedings
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Unpublished studies
Contacting pharmaceutical companies or
equipment manufacturers
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Key advantage of searching
bibliographic databases
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Can be searched electronically for:
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words in the title and abstract
Standardized indexing terms or controlled
vocabulary assigned to each record based
on the full report.
Limitations and challenges of
electronic searching for published
studies
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Selected journals and journal years indexed
Conference proceedings and books in selected databases
only
A complex tailor-made strategy required for each database
Poor indexing often limits retrieval
Titles and abstracts (when available) may be insufficiently
detailed for text word searching
Free-text searching for full-text electronic journals!
High sensitivity searches result in low precision
Handsearching
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Advantages
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All reports of trials in journal
Articles, editorials, letters, abstracts, news items
Journals, books and conference proceedings not in
electronic databases
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Recent issues
Limitations
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Time consuming and expensive
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Large numbers of healthcare journals
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Access to journals
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Non-English language journals
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Subject to human error
Is handsearching worthwhile?
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Complete retrospective search of 32 years of journal
STROKE
Compared with MEDLINE search of STROKE for same
publication years
MEDLINE search identified 44% of 803 stroke trial
reports identified by handsearching.
Conference abstracts and letters etc not indexed by
MEDLINE
Many of the trials published as conference abstracts
will not come to full publication
Stroke Group
general strategy
modified for each database
STROKE
specific
strategy
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Highly
sensitive
TRIALS
strategy
Screened for stroke trials
Review-specific
intervention-based strategy
STROKE
specific
strategy
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?
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Screened for
additional
relevant trials
Highly
sensitive
Cochrane
TRIALS
strategy
Review specific
INTERVENTION-based
strategy
New developments that
make life easier
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Increasing availability of electronic journals
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77% of relevant MEDLINE trial reports in 2006
Free open access journals and conference proceedings
More detailed reporting of study methods
Increasing numbers of ongoing trial registers
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Including drug company (eg GlaxoSmithKline, Novartis,
Roche)
International trial registration
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WHO International Clinical Trials Registry Platform
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Multiple Registers (ISRCTN, NCT, ANZCTR)
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Universal Trial Reference Number
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Easier to track trial reports and link to studies
Looking for Research Studies?
How to search like a professional!
Increasing numbers of
resources available
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Need a focused approach using high
quality information resources
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Increased use of electronic sources
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Efficient search strategies
Where do we start?
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Search question?
Purpose of search?
How much information do we need?
Where do we look?
How much time do we have?
How much money do we have (if any!)?
Sources of Bias
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Publication bias
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“Level of publication” bias
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Cited work is more likely to be positive
Electronic database bias?
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abstracts and letters may more often report
negative results
Reference/citation bias
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negative results are often not published
Need to search multiple databases
Language bias
Aim to minimize bias
Bibliographic Databases
MEDLINE
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Major general medical database
Indexes articles from >5000 journals (2100 not EMBASE)
37 languages
>16 million citations from 1950
All articles indexed using Medical Subject Headings (MeSH) to
describe each article
Available on Ovid SP through University or NHS e-Library
Bibliographic Databases
EMBASE
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Major general medical database
Indexes articles from 4800 journals (1700 not MEDLINE)
30 languages
>11 million citations from 1974
All articles indexed using Emtree Headings to describe each
article (Different from MeSH)
Pharmacological studies indexed in greater depth than
MEDLINE
Available on Ovid SP through University or NHS e-Library
Both databases required for a comprehensive search
MEDLINE Record
searchable fields
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Authors
Title
Journal title
MeSH Subject Headings
Abstract
Publication Type
Language
MEDLINE
Developing a Search Strategy
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Use a combination of MeSH terms and free text for:
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Disease under investigation
Intervention
Study design (methodological filters)
Use “Publication Type” field to focus the type of research (eg
randomised controlled trial)
Apply other logical limiters (eg age group, human, time period)
Ask your local medical librarian for help!
Stem Cell Transplantation for ischemic stroke
MEDLINE (Ovid)
1. cerebrovascular disorders/ or basal ganglia cerebrovascular disease/ or exp brain ischemia/ or carotid
artery diseases/ or carotid artery thrombosis/ or intracranial arterial diseases/ or cerebral arterial diseases/ or
exp "intracranial embolism and thrombosis"/ or exp stroke/
2. (isch?emi$ adj6 (stroke$ or apoplex$ or cerebral vasc$ or cerebrovasc$ or cva or attack$)).tw.
3. ((brain or cerebr$ or cerebell$ or vertebrobasil$ or hemispher$ or intracran$ or intracerebral or
infratentorial or supratentorial or middle cerebr$ or mca$ or anterior circulation) adj5 (isch?emi$ or infarct$ or
thrombo$ or emboli$ or occlus$ or hypoxi$)).tw.
4. 1 or 2 or 3
5. cell transplantation/ or stem cell transplantation/ or cord blood stem cell transplantation/ or hematopoietic
stem cell transplantation/ or mesenchymal stem cell transplantation/ or peripheral blood stem cell
transplantation/
6. stem cells/ or adult stem cells/ or embryonic stem cells/ or fetal stem cells/ or fibroblasts/ or hematopoietic
stem cells/ or myeloid progenitor cells/ or erythroid progenitor cells/ or mesenchymal stem cells/ or
multipotent stem cells/ or exp myoblasts/ or pluripotent stem cells/ or totipotent stem cells/ or tumor stem
cells/
7. exp cells/tr
8. ((stem or progenitor or embryo$ or fetal or foetal or umbilical or bone marrow or cord blood) adj5 (cell or
cells)).tw.
9. (cell adj5 (transplant$ or graft$)).tw.
10. (fibroblast$ or myoblast$).tw.
11. cell transplantation.jn.
12. 5 or 6 or 7 or 8 or 9 or 10 or 11
13. 4 and 12
14. limit 13 to humans
Search results
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Review retrieved citations
Modify search strategy
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New text word terms
Synonyms, related terms, variant spellings
Check MeSH headings
Check that search strategy identified known
references
Gradually build a comprehensive strategy
Features of reference
management software
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Personal reference database
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organise references
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create bibliographies
Imports references from various databases
Automatic formatting of papers and bibliographies
Reference Manager, EndNote
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Locally installed or networked
EUCS provides half-day courses on Reference Manager and
EndNote in almost every month of the year
Conclusions
Be systematic but realistic!
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Clearly define search question
Identify relevant available sources
Prepare search strategy(ies)
Conduct and modify search
Consider reference management software
Translation?
Correctly document and report the search methods
Essential Reading
Cochrane Handbook for Systematic Reviews of
Interventions
Chapter 6 Searching for studies
•Main sources of potential studies
•Planning the search process
•Designing and carrying out the search strategies
•Managing references
•Correctly documenting and reporting the search
process
http://www.cochrane.org/resources/handbook/