How to do a literature search

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


• 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.


• 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

• Types of evidence • Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your 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)



• Types of evidence

• Formulating answerable questions• Sources of evidence• Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching


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?




• Formulating answerable questions

• Sources of evidence • Search techniques• Optimal search strategies• Online tools• Evaluating your literature searching


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




• Formulating answerable questions

• Sources of evidence

• Search techniques • Optimal search strategies• Online tools• Evaluating your literature searching


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)


• 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


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”


• 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


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

Google

• 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


• 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


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

2

HOW TO USE OVIDPRACTICAL SESSION

1. Log in

2. Klik

Scroll down

Klik Ovid

1

2

3

1. Keywords/Boolean

2. Limit

Task

• To perform literature search on.....

1

2

3

1

2

34

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

1

1

1

2

1

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….

Documents

How to do a literature search