How to do a literature search

Andrew Booth (University of Sheffield) and Mary Dixon-

Woods (University of Leicester)

This course will cover:

• The role of the literature review [10 mins]• Types of evidence [5 mins]• Formulating answerable questions [10 mins]• Sources of evidence [12 mins]• Search techniques [30 mins]• Optimal search strategies [10 mins]• Evaluating your literature searching [10 mins]• Evaluation [3 mins]

How to do a literature search

• The role of the literature review

The role of the literature review - 1

1. Exposes main gaps in knowledge [and] identifies principal areas of dispute and uncertainty (Mays et al, 2001).

2. Helps identify general patterns to findings from multiple examples of research in the same area.

3. Juxtaposing studies with apparently conflicting findings helps explore explanations for discrepancies.

The role of the literature review - 2

4. Helps define your terminology or identify variations in definitions used by researchers or practitioners.

5. Helps to identify appropriate

research methodologies.

6. You can also identify validated scales and instruments.

Case study: Attitudes of different professions to handwashing in a delivery

suite - 1

• A midwife is researching attitudes of different staff to handwashing. She firstly searches the literature to focus the scope of the original question.

• Although the literature on handwashing is vast she needs to discover whether published research has been conducted specifically in obstetrics and gynaecology settings. Has anyone researched the topic specifically in a delivery suite?

Case study: Attitudes of different professions to handwashing in a delivery

suite - 2

• “Handwashing” has many more definitions than she had envisaged.

• Does handwashing include the use of a handrub? Does it constitute use of water only? What is the minimum duration of the procedure before it is classed as "handwashing"?

• The literature search enables her to explore different definitions of her main concepts.

Case study: Attitudes of different professions to handwashing in a delivery

suite - 3• Are there validated instruments to

measure attitudes to handwashing (or towards routine hospital hygiene)?

• The literature review may inform selection of appropriate outcomes - those employed in previous studies (literary warrant) or those considered appropriate by the relevant clinical community (user warrant).

• Will she focus singly on attitudes or will she investigate knowledge and/or behaviour?

Q: Any other roles or uses for literature review that you have

identified?

How to do a literature search

• The role of the literature review [10 mins]

• Types of evidence

Some types of evidence

• Prediction – Models, case studies (single and multiple), 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)

Exercise: What types of “evidence” are relevant to your

question?

How to do a literature search

• The role of the literature review [10 mins]

• Types of evidence [5 mins]

• Formulating answerable questions

Formulating answerable questions

• Translates “Aims” into achievable and focused tasks

• Helps to distinguish main from subsidiary questions

• Helps to identify the likely research designs to answer the research question

• Helps in constructing the literature search

Why?

• "Ask a poor question and you will get a poor review. A clear question also helps the reader rapidly assess whether the review is relevant to his or her own…practice". (Counsell, 1997)

• Clearly framed questions "guide much of the review process including strategies for locating and selecting studies or data, for critically appraising their relevance and validity, and for analysing variation among their results". (Cochrane Handbook)

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?

Q: What type of question is your PhD question?

A structure for formulated questions

Health services research uses PATIENT-

INTERVENTION-COMPARISON-OUTCOME (PICO) structure

Within social sciences research the following may be more appropriate:SETTING

POPULATION

INTERVENTION

COMPARISON

EVALUATION

An example of SPICE [Actual PhD example]

• SETTING – UK Marine Conservation

• POPULATION – public, private and voluntary sector organisations

• INTERVENTION - partnership approaches

• COMPARISON – [Unilateral approaches or other countries’ approaches]

• EVALUATION – achievement of strategic marine conservation objectives

An example of SPICE [Actual PhD example]

• SETTING – UK Television Industry

• POPULATION – Women

• INTERVENTION – None

• COMPARISON – [With men or with other industries]

• EVALUATION – historical, political, organisational and practical issues

Try one!

• What is the effect of secondary school headteachers’ leadership and management strategies on student achievement, attitudes, behaviour and recruitment?

Exercise: Now you try! Use the SPICE framework to formulate

your own research question

Scenario – A fistful of doulas?

• You are working on an ESRC funded project looking at the benefits of a doula (a woman experienced in childbirth who provides continuous physical, emotional, and informational support to the mother before, during and just after childbirth) for low-income mothers.

Our example of SPICE

• SETTING – the Developed World (with comparable health systems to the UK)

• POPULATION – Low-income mothers • INTERVENTION – Doula (Lay support)• COMPARISON – Professional support [or

No Support] • EVALUATION – Perceived levels of social

support, birth outcomes, levels of breastfeeding etc.

How to do a literature search

• The role of the literature review [10 mins]

• Types of evidence [5 mins]

• Formulating answerable questions [10 mins]

• Sources of evidence

Stages in the literature search process

• Focus your question• Decide on the most appropriate sources• Perform a scoping search by:

– Dividing your search into a series of ‘concepts’– Thinking of alternative terms for each concept– Searching each concept separately– Combining concepts using Boolean logic– Limiting your search

• Revise your search, as necessary, and replicate in other sources

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

Sources

• Electronic databases:

– Evidence-based• The Cochrane Library, Clinical Evidence, etc.

– Subject specific• ERIC, EconLit, Medline, PsycLit, Cinahl, British

Nursing Index, AgeInfo, Biological Abstracts, etc.

– Related disciplines• LISA, ASSIA, British Humanities Index, Web of

Science (Science, Social Sciences, Arts & Humanities Citation Indexes), etc.

Reflective Exercise

• Which of the listed databases might be of relevance to this topic?

[N.B. We are going to search Web of Science and Ovid Medline/CINAHL]

How to do a literature search

• The role of the literature review [10 mins]

• Types of evidence [5 mins]

• Formulating answerable questions [10 mins]

• Sources of evidence [12 mins]

• Search techniques

From: Etext on Health Technology Assessment (HTA) Information Resources. Chapter 4: Searching MEDLINE/PubMed for Health Technology Assessment Information by Viveka Alton and Ione Auston. http://www.nlm.nih.gov/nichsr/ehta/chapter4.html

Take Home Message – 1An optimal search will combine natural language and controlled

vocabulary approaches

Natural language

• Uses your own words and searches words & phrases (typically from the title, abstract & keyword fields) to retrieve records

• Potentially can search any field of a database• Can be very precise (but there can be ambiguities e.g.

Moderation [exam process] and Moderation [within reasonable limits] )

• 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

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. (But comp* would find compost!)

• 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

Controlled vocabulary

• Maps variations in terminology to a single “approved” word or phrase (e.g. Toyota, Rolls Royce, Mini, Ferrari etc. all mapped to “Automobiles”)

• Can demonstrate hierarchical or conceptual relationships (e.g. Europe-UK-England-Hampshire-Southampton)

• May not exist for new terms (e.g. “single currency”)

• May not map to a precise term (e.g. “teaching techniques” for “problem based learning”)

Database features to support controlled vocabulary

• A Thesaurus (e.g. MeSH, ERIC) [NB. Opposite direction to Roget’s Thesaurus – Many-to-One]

• Mapping

• Explode functions

• “See Under”, “Used For” and “See Also” references

Mapping

Vocabulary mapping uses statistical analysis to determine which subject headings (index terms) occur most frequently in documents

containing your free text query.

Thesaurus

A controlled vocabulary arranged in a known (e.g. alphabetical or hierarchical) order containing:– Preferred terms (keywords) – non - preferred terms (synonyms ...) – Semantic Relations (Broad Term,

Narrow Term, Related Term) – Scope notes

What practical problems would you encounter if you used the following

search terms?• Postqualifying (2 problems)

• Labour support (3)

• PMT (2)

• Stroke (2)

• Public school (3)

• Aids (2)

• Adolecent (2)

Take Home Message – 2Getting unexpectedly few results

can be worse than getting no results at all – “satisfied but

inept”!

ExplosionsPregnancy    

Childbirth      Childbirth, Premature     Vaginal Birth       

Vaginal Birth After Cesarean    Labor      

Cervix Dilatation and Effacement      Labor Pain     Labor Presentation     Labor Stages      Uterine Contraction

broad search

specificsearch

exploded

Boolean - OR

DOULAS OR LABOUR SUPPORT

DOULAS

LABOUR SUPPORT

Use to combine like terms or terms within the same concept

Boolean - AND

CHILDBIRTH

CONTINUOUS SUPPORT

CHILDBIRTH AND CONTINUOUS SUPPORT

Use to combine together different concepts

Boolean - NOT

DOULA NOT MIDWIFE

DOULA

MIDWIFE

Use to exclude terms from your search

Using Boolean in your strategy

POPULATION INTERVENTION

EVALUATION

CHILDBIRTH

OR

LABOUR

DOULAS OR LAY

SUPPORT

ATTITUDES, VIEWS,

OPINIONS AND AND

x

x

Citation searching (Web of Science feature)

Find a key reference from (at least) last 5-10 years and follow

all references that cite it

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)

Related records

EITHER on the basis of frequency of common subject headings (MEDLINE)

OR on the basis of frequency of common citations (Web of Science)

How to do a literature search

• The role of the literature review [10 mins]

• Types of evidence [5 mins]

• Formulating answerable questions [10 mins]

• Sources of evidence [12 mins]

• Search techniques [30 mins]

• Optimal search strategies

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 (and usually tested) for use with particular databases and/or search interfaces to retrieve specific types of evidence, study design or …information more effectively”

Example 1 – Qualitative Research

Qualitative Research/ ORQuestionnaires/ ORexp Attitude/

findings ORinterview$ ORInterviews/ ORqualitative

Example 2 – User Views

Exp Attitude/

Attitude$ OR

(user$ adj view$) OR

opinion$

How to do a literature search

• The role of the literature review [10 mins]• Types of evidence [5 mins]• Formulating answerable questions [10 mins] • Sources of evidence [12 mins]• Search techniques [30 mins]• Optimal search strategies [10 mins]• Evaluating your literature searching • Evaluation [3 mins]

Evaluating your search strategy

Relevant Not Relevant

Retrieved Use to generate additional search terms

Eliminate terms with poor yield

Not Retrieved Use reference lists from key articles to identify these

No further action required

Take Home Message 3: Judge not by what you have retrieved

but by what you may have missed!

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, etc.

Sources of help

• Your local University library

• Database help pages• Web-based teaching

materials• Reading List

How to do a literature search

• The role of the literature review [10 mins]• Formulating answerable questions [5 mins] • Types of evidence [10 mins]• Sources of evidence [12 mins]• Search techniques [30 mins]• Optimal search strategies [10 mins]• Evaluating your literature searching [10 mins]• Evaluation

Evaluation

• Identify one thing that you will do when you get back to work as a result of today’s workshop

• Identify one aspect of today’s workshop that you will need to explore further.