Transcript Systematic Searching of the Literature

Systematic Searching
of the Literature
Canadian Partnership Against Cancer:
Atlantic Clinical Practice Guideline
Workshop
October 16 and 17, 2008
Halifax, Nova Scotia
Seana Collins MA, MLIS
[email protected]
Librarian Educator
Capital District Health Authority
Systematic Searching
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The systematic identification of evidence is
an essential step in clinical guideline
development. (NICE Guidelines Manual, April 2008, p. 48)
Systematic Searching
There are several steps involved in developing and
executing a literature search:
1. Formulate an “answerable” question - PICO
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Identify key search concepts
3. Structure the search strategy using Boolean Logic
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Consider the question domain: therapy? diagnosis? prognosis? etiology?
5. Consider the type of information required to answer the question:
background information?
foreground information?
6. Consider the sources of evidence: (core databases, subject databases
etc.)
Systematic Searching
7. Run a preliminary or “scoping” search (What are the existing guidelines?)
8. Execute a comprehensive literature search (database searching, sources of
guidelines, subject specific databases)
9. Evaluate the search results: too broad? too narrow? relevant?
10. Refine the search results using appropriate LIMITERS: age group, gender,
publication date range, study design etc.
11. Document search results
12. Manage and capture search results (RefWorks, EndNote, ProCite,
Reference Manager, etc.)
1. Formulate the Question
Begin by composing a clear, well stated question.
Ambiguous questions will often lead to ambiguous
search results.
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Write down your research topic or question
Underline or circle the most important concepts
These will be your search terms
Example Question:
Use of marijuana for treating cancer.
Formulate the research topic into an “answerable”
question using PICO.
PICO
PICO is a tool used in evidence base research methods to help identify
key concepts and articulate an “answerable question”.
P - Population (patient)
What is the patient group or condition being assessed?
I - Intervention
What is (are) the interventions being considered?
C – Comparison Intervention
Is there a comparison being considered?
O - Outcome
What is the expected outcome?
PICO
Our Research Topic:
Use of marijuana for treating cancer.
Population = cancer patients
Who are the patients of interest?
 Is there a particular age group, gender or population?
 What is the health concern?
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Intervention = marijuana
What therapeutic, diagnostic, preventive or other health care interventions are you
interested in knowing more about?
 What health care management strategies are you interested in comparing?
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Comparison = none
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Is there a comparison to be evaluated against the intervention?
Only used if more than one intervention, or if no intervention is a factor.
Outcome = improved quality of life
What is the desired outcome to be evaluated?
 How will the patient or population be affected, or not affected, by the intervention?
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1. Formulate the Question
Our Question:
Use of marijuana for treating cancer.
“Answerable” Question:
Is marijuana an effective treatment in improving the
quality of life for cancer patients?
Using PICO to formulate a question can help to identify concepts that
can be used to structure your search strategy.
2. Identify Key Concepts
Identify each specific concept in the question to be searched:
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Using our example our search concepts would be:
treatment and cancer and marijuana
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One could simply enter these terms into a database and search:
treatment AND cancer AND marijuana;
however, this would mean:
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any papers where the term neoplasms is used in place of cancer
would be missed
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any papers where the the terms: treat or treatments or therapy is
used in place of treatment would be missed
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You would also retrieve papers that have a passing reference to the
topic and are not useful (not specific or relevant)
2. Identify Key Concepts
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Use appropriate thesauri or controlled vocabularies, such as
MeSH (PubMed/Cochrane) or other subject listings to translate
individual concepts into valid subject headings. (EMTREE
Headings, CINAHL Headings)
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Verify if any of your subject terms can be translated to MeSH
subheadings.
• If an appropriate subject heading can not be found, consider doing a
keyword search.
• When keyword searching, remember to use truncation, when
keyword searching for compound words or phrases use quotations
i.e. “health services”.
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Truncation: Symbols which instruct the database to find all
word variants and endings (*,$,#). Example: surg$ will retrieve:
surgery, surgeon and surgical.
3. Construct the Search Strategy
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Search terms or “search statements” are organized by concepts
or terms which are then combined using Boolean Operators:
AND, OR, NOT.
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It is very helpful to write out your search strategy with the relevant
Boolean Operators (OR, AND, NOT) before executing the search in
the database.
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Example: cancer OR neoplasms AND treatment OR therapy AND
marijuana
Identify similar terms or synonyms
• Connect search terms using Boolean Operators
• Consider phrase searching, some databases such as PubMed and
Cochrane Library will search for phrases. Put the terms in “quotation
marks” to indicate a phrase: example: “sleeping sickness”
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Boolean Logic
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‘Boolean Logic’ uses the logical relationships OR, AND,
NOT, to create relationships between concepts or
subject headings.
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Understanding and application of Boolean logic
correctly has become fundamental to all online
searching.
OR
AND
NOT
3. Construct the Search Strategy
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It is often very helpful to write out your concepts
using a table to assist in organizing your search:
Your Concept
marijuana
cancer
treatment
MeSH
cannabis
OR
neoplasms
OR
therapeutics
OR
weed
carcinoma*
therap*
keywords
Possible search strategy: (neoplasms OR carcinoma*) AND (therapeutics
OR therap*) AND (cannibis OR weed)
4. Consider Question Domain
Consider the question domain or the clinical study
category of your question, this will assist you in
assessing the results of your search (applicability).
therapy question?
 Clinical studies that discuss the treatment of diseases
diagnosis question?
 Clinical studies addressing disease diagnosis
prognosis question?
 Clinical studies addressing disease prognosis
etiology question?
 Clinical studies addressing causation/harm in disease and diagnostics
4. Consider Question Domain
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The consideration of question domain will assist you in
identifying the type of clinical studies that would best
answer your question. (RCT, meta-analysis, systematic
review, cohort study, practice guideline, etc.)
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In addition it will assist you to identify key appropriate
resources to search for literature on your question.
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Some information resources are stronger in terms of
therapeutics (Cochrane Systematic Reviews) others may
be stronger in diagnostic questions (Health Technology
Assessment Database).
5. Type of Information
Consider the type of information or evidence
you are looking for.
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Is it background information? If so, it is likely that you
will need to search/consult a textbook. (Harrison’s Principles
of Internal Medicine, MD Consult, 5 Minute Clinical Consult,
or a Library Catalogue)
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Is it foreground information? If so, you will need to
search the primary literature, it is likely that you will have to
conduct a literature search in a bibliographic database.
(PubMed, Cochrane, EMBASE etc.)
6. Resources
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What are considered to be the core resources for your subject area?
are these resources available to you?
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Identify the subject database most relevant to your research
question.
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What type of database is it? bibliographic? textual? (fulltext)
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Review how each database works, does it use controlled vocabulary?
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Consult a Librarian and/or your institution’s Library for a list of
resources
Guidelines:
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Are there established guidelines for specific resources that must be
consulted for the type of study you are conducting? i.e. Cochrane
Manual (systematic reviews), NICE Guidelines Manual, CMA
Guidelines Manual, ADAPTE Manual (guideline adaptation)
6. Sources of Evidence
Core Databases:
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Cochrane Database of Systematic Reviews – CDSR
(Cochrane reviews)
Database of Abstracts of Reviews of Effects – DARE (other
reviews)
Cochrane Central Register of Controlled Trials – CENTRAL
(clinical trials)
Health Technology Assessment (HTA) database
MEDLINE/MEDLINE In-Process (PubMed)
EMBASE
CINAHL (Cumulative Index to Nursing and Allied Health
Literature)
6. Sources of Evidence
Subject Specific Databases:
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PsycINFO
AMED
ERIC
PEDro
AGELine
Other Sources of Evidence:
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Guidelines: i.e. National Guidelines Clearinghouse
Controlled Trial Registries
UK Clinical Research Network
National Research Register (NRR) Archive
Web of Science / Scopus
Conference Papers and Dissertations Indices
7. Preliminary Search
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It is essential to run a preliminary search to determine if your topic is well
published and to determine the level of published evidence available on
your topic.
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If you are conducting a systematic review of RCTs for example, and only
one RCT has been published on your topic, it may impact on the validity of
your study.
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Run the preliminary search in the most comprehensive and relevant
database to your topic. (Within biomedicine, and for English speaking
researchers, this will likely be PubMed.)
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Most importantly a preliminary literature search will allow you to review
search results and determine whether or not your initial search strategy
needs to be adjusted.
7. Preliminary Search
Based on the preliminary or scoping search you may
decide to limit your search results to a specific
population group, or Intervention.
Consider:
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Checking the indexing of the relevant articles retrieved in your
search results for additional subject headings or terms that can be
incorporated into your search strategy.
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Scanning the abstracts of the results to determine whether you
have used the appropriate subject term(s) and relevant key words.
A preliminary search will also save you time and effort in terms of
sensitivity versus precision.
Sensitivity versus Precision
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It is important that searches for systematic reviews
attempt to identify all the relevant literature.
However, there needs to be a trade-off between
conducting an exhaustive search that will require
additional resources versus undertaking a more
modest search that may miss some studies.
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The preliminary / scoping search can help to
identify key studies for a review question that can
assist in balancing the search sensitivity.
8. Execute Full Search
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Start by executing a search using broad subject terms.
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Use key words, including all relevant synonymous terms
and word variants in combination with your subject
terms. The goal is to be as comprehensive as possible.
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You can refine and focus the search after you have a set
of broad results to limit.
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Use limiters and inclusion / exclusion criteria to focus
and refine your search.
Refine the Search
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To decrease search result numbers, consider the use of
limiters.
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Most databases allow users to limit or refine search
results to specific criteria. Some examples include:
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Publication date(s) range
Language
Publication type (i.e. Review, Letter, Comment etc.)
Age group
Gender (i.e. Male / Female)
Study-design (i.e. systematic review, guideline, randomised controlled trial)
Using limiters to refine your search can provide you with a method
to review a manageable number of abstracts, especially if you are
searching a very large database such as PubMed.
9. Evaluate Search Results
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Evaluate your search results, are the results what you expected
based on your research question?
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Is the evidence reliable? valid?
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Are the results applicable to your patient population?
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If your search results are satisfactory utilize the same concepts to
expand and build on your search results using other subject specific
databases.
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Basic literature searching skills are transferable from one resource
to another. The basic principles are the same it is the controlled
vocabulary and the resource search interface that may differ from
database to database.
9. Evaluate Search Results
If your search results are not satisfactory consider the following:
Re-assess your search question:
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Have you used the best subject terms to represent the search concepts?
For example: perhaps a broader subject term should be used to capture
more results?
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Have you used a keyword search in combination with your subject
search to represent concepts?
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Are your results too narrow? Are your limiters appropriate? For example,
have you excluded useful search results by applying too restrictive limits:
publication date range? age group? study-design? etc.
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Are your results too broad? for example should you exclude similar subject
terms that are often associated with one another. For example:
glucosamine NOT condroitin
dementia NOT Alzheimer’s Disease
9. Evaluate Search Results
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Have you used the most appropriate databases or
resources for your search?
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Have you searched all available sources of guidelines?
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Consult an expert, ask a Librarian or members of
your Guidelines Group to review your search strategy.
10. Document the Search
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Literature searches must be thorough, transparent and
reproducible.
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It is essential that literature search methods be
documented.
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Provide the search strategies used for each database so
that they can be replicated.
10. Document the Search
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Provide details of which databases you searched (e.g.
MEDLINE, EMBASE, CENTRAL, etc.)
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Ensure that you record when you searched the
database this might include:
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The name of the database searched
The name of the host/system/vendor/interface used
The date when the search was run
The years covered by the search (all Limiters used)
Filename for search strategy (e.g. Embasestrategy.txt)
Filename for search results (e.g. Embaseresults.txt)
11. Manage Search Results
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Once you have completed the literature search, ensure that all
of your search results have been saved, emailed, printed, or
exported. Each resource will provide this functionality.
Note:
• If the databases you have used provide user accounts or
registration, it is a good practice to take advantage of this
option. It will allow you to save search strategies
and results for future use,
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This will also allow you to view your search results at any time
to refine, adjust, or update and your search.
11. Managing Search Results
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Capture your research results using bibliographic
management software such as RefWorks,
EndNote, ProCite, Reference Manager.
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This will allow you to archive your references,
produce a formatted bibliography or list of
references in any citation style you may require.
11. Managing Search Results
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In addition to archiving references, reference
management software can be used for:
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Coding the references with additional information
Providing links to the full text of articles
Tracking the ordering and/or receipt of documents
Linking to word processing software output styles to
automatically cite while writing.
It is essential to document and manage all search
results in order to maintain transparency and the ability
to replicate search results.
Exercise #2:
Clinical Scenario:
A middle aged woman presents in family clinic
complaining of severe joint pain, stiffness,
and swollen hands and feet. She has a
family history of osteoarthritis and wants to
know if taking glucosamine supplements will
improve her pain and stiffness.
What is the question?
PICO:
Patient / population: middle aged woman
(condition) osteoarthritis
Intervention (s): glucosamine
Comparison (s): no glucosamine
Outcome: improve mobility and pain
“Answerable” Question:
In adult patients with osteoarthritis, is glucosamine
effective in reducing pain and improving function?
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Exclusion Criteria: NOT chondroitin
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Possible Limiters: middle aged women (age
group), systematic review, guideline, RCTs