How to do a literature search
Saharuddin Ahmad
Aida Jaffar
Department of Family Medicine
Outline
• The role of the literature review • Types of evidence• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching
How to do a literature search
• The role of the literature review• Types of evidence• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature search
The role of the literature review
• Exposes main gaps in knowledge and identifies principal areas of dispute and uncertainty (Mays et al, 2001).
• Identify findings from multiple examples of research in the same area.
• Explore explanations for discrepancies.
The role of the literature review
• Define terminology or identify variations in definitions used by researchers.
• Identify appropriate research
methodologies.
• Identify validated scales and instruments.
The role of the literature review
How to do a literature search
• The role of the literature review
• Types of evidence • Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature search
How to do a literature search
Types of evidence
• Prediction – Models, case studies ,documentary analysis
• Historical – documentary analysis, case studies, narratives
• Intervention – experimental studies• Exploration – literature review, theory building,
consensus processes• Attitudes – psychological research• Qualitative - using specific qualitative techniques • Causation – observational studies (e.g. case
control)
How to do a literature search
• The role of the literature review
• Types of evidence
• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching
How to do a literature search
Formulating answerable questions
• Translates “Aims” into achievable and focused tasks
• Helps to identify the likely research designs to answer the research question
• Helps in constructing the literature search
PICO
A method to formulate a precise question :
• Population
• Intervention
• Comparison
• Outcome
Problem : Would aspirin reduces CVD events in diabetics?
Final question :
For patients with diabetes mellitus, will aspirin prophylaxis produces fewer cardiovascular overall complications?
Item Description
Population Patients with diabetes
Intervention CVD events with aspirin
Comparison Compared to method of ‘no aspirin’
Outcome Fewer for all morbities and mortalities
PICO
Some types of question
• Prediction – What is the likely result of X?• Historical – How have we got from A to B?• Intervention – Is doing Y better than doing Z?• Exploration – What are the possible explanations for A?• Attitudes – How do people feel about B?• Causation – What are the likely causes of C?• Measurement – What is the size of X, how often does it
occur etc?• Characterisation – How can we understand and specify W?
How to do a literature search
• The role of the literature review
• Types of evidence
• Formulating answerable questions
• Sources of evidence • Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching
How to do a literature search
SOURCES
Referencelists
Databases
Contact withresearchers/practitioners
Greyliterature
Pharmaceuticalindustry
Research
Handsearching
Conferenceproceedings
Citationindexes
Generale.g.
ASSIA
Subject specific
e.g. MEDLINE
Evidence-based
Registers
Research Councils
Publishedcopies
Indexes
OPACs
Databases
InternetDirectcontact
How to do a literature search
• The role of the literature review
• Types of evidence
• Formulating answerable questions
• Sources of evidence
• Search techniques • Optimal search strategies• Online tools• Evaluating your literature searching
How to do a literature search
http://www.nlm.nih.gov/nichsr/ehta/chapter4.html
Search term / Key words
• Uses your own words and searches words & phrases to retrieve records ie diabetes, aspirin, ischaemic heart disease
• Some problems:– Plurals: e.g. child or children– Different spellings: e.g. esthetic or aesthetic– Different terminology: e.g. pavement or sidewalk – Prefixes: prenatal, pre natal, pre-natal – Different names : Type II diabetes, diabetes mellitus, diabetes
Database features to support natural language
• Truncation (e.g. *, $) used to search for different word stems and word endings– e.g. use comput* to find computer, computers,
computed, computing, etc.
• Wild cards (e.g. *, ?) used to search for spelling variants– e.g. use leuk*mia to find leukaemia or leukemia
• Proximity and adjacency operators (e.g. adj or near) – e.g. motor near2 accidents
Database features to support controlled vocabulary
• A Thesaurus e.g. MeSH – medical subject heading terms)
• Mapping
• Explode functions
• “See Under”, “Used For” and “See Also” references
Boolean - OR
DM OR ED
DM
ED
Use to combine like terms or terms within the same concept
Boolean - AND
DM
ED
DM AND ED
Use to combine together different concepts
Boolean - NOT
DM NOT ED
DM
ED
Use to exclude terms from your search
Other search techniques
• Reference chaining: Follow up references from reference lists of relevant articles
• Hand searching: Identify key journals in your field and browse them cover to cover
• Relevance feedback: Look at subject indexing for a key reference and use to modify your search terms (Also “See Related Records” features)
How to do a literature search
• The role of the literature review• Types of evidence• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching
How to do a literature search
What is an optimal search strategy?
“optimal permutations of search terms found in the titles, abstracts or the subject indexing of relevant articles that have been demonstrated to have a high correlation with study quality”
“pre-prepared search strategies, previously referred to as ‘search filters’, ‘quality filters’, ‘hedges’ or ‘optimal search strategies’ developed for use with particular databases to retrieve specific types of evidence more effectively”
How to do a literature search
• The role of the literature review• Types of evidence• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online Tools• Evaluating your literature searching
How to do a literature search
Online Tools
• Google Scholar
• Portal Perpustakaan PPUKM
• Pubmed
• Ovid
• Science direct
• Scopus
• Springer links
Google Scholar
• Using Boolean ExpressionsNOT (minus sign)
• ED –DM • Search for ED while excluding DM from results
• Exact strings“Diabetes mellitus”, “erectile dysfunction”
If results is too large, use the “Search within results” option
• Wildcards ‘*’/’?’ - Replace wildcard with any combination
of characters
DM* or T2DM* - DM? or T2DM?
• Site search – Restrict your search to a particular site– site:domain.com– Example: cluster computing site:*.edu
Google Scholar
library.oakland.edu/coursePages/handouts/wildcards.pdf
Wildcards
The National Library of Medicine
• Part of the National Institutes of Health (NIH)• The world’s largest biomedical library; it
produces:
– PubMed = Index to world’s biomedical literature
– MedlinePlus = Patient education & consumer health information
– ClinicalTrials.gov = Database of clinical trials
MEDLINE
• The world’s largest biomedical database
• Over 5,000 journals indexed, with worldwide coverage
• Covers all aspects of biosciences and healthcare
• Database of 16+ million journal citations, 1950 to the present
• 90% are in English ; 79% have abstracts
• The primary component of PubMed
PubMed
• PubMed is a tool to search:
– MEDLINE (1950 to present)– In-process & publisher-supplied citations (some before they are published in
hard copy)– Citations from some older materials not yet upgraded with MEDLINE
indexing, some out-of-scope articles from MEDLINE journals, and some life sciences journals that submit full text to PubMedCentral
• Produced by NCBI– National Center for Biotechnology Information, part
of NLM
• Accessible worldwide on the Web at no charge
How to do a literature search
• The role of the literature review• Types of evidence• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching
How to do a literature search
Evaluating your search strategy
No further action required
Use reference lists from key articles to identify these
Not Retrieved
Eliminate terms with poor yield
Use to generate additional search terms
Retrieved
Not RelevantRelevant
And finally …
• Documenting a search– Helps to avoid duplication,
allows replication in future– e.g. date of search, sources
searched, no. of hits, details of strategy, etc.
• Reference management– Reference Manager,
EndNote, wizfolio etc.
Managing data
No First author
Year Prevalence Objective Remarks
1 2
1 Awang 2011 60% Significanthypothesis
Not sigreason
Important pointsSuggestions etc
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HOW TO USE OVIDPRACTICAL SESSION
1. Log in
2. Klik
Scroll down
Klik Ovid
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1. Keywords/Boolean
2. Limit
Task
• To perform literature search on.....
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HOW TO USE PUBMEDPractical session
• Let’s use this search:
What’s the evidence for the use of montelukast in the management of childhood asthma
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HOW TO USE PUBMEDPractical session
1. Create new folder
2. Create ‘asthma’ file
1. Search topic
1. Click,drag and drop at the ‘asthma’ file
2. Drop here
1. Click,drag and drop at the ‘asthma’ file
1. Locate PDF :Wizfolio will locate the article
End of the beginning….