How to do a literature search

Saharuddin Ahmad

Aida Jaffar

Department of Family Medicine

Outline

• Formulating answerable questions• Search techniques• Optimal search strategies• Evaluating your literature searching

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

Search techniques

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

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”

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

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 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

THANK YOU