How to Conduct a Literature Review (ISRAPM 2014)

Saeid Safari
MD, Anesthesiologist
Editorial Manager of Anesthesiology and Pain Medicine
drsafari.s@gmail.com
How to Conduct a Literature Review
Searching references in medical journalism

S a e i d S a f a r i
Objectives
 List four categories of information resources
 Apply selection criteria to identify appropriate
information resource
 List five databases to find primary studies
 Strategize and execute a systematic, explicit and
reproducible search of the biomedical literature

Searching for scientific problem
Review of literature
H y p o t h e s i s
Aims of research
M e t h o d s
Plan of research
Research
Results
Researchers work in graphic form
Aztec Pyramide

What’s a Research Lit Review?
A research literature review is a systematic, explicit and
reproducible method for identifying, evaluating, and synthesizing
the existing body of completed and recorded work produced by
researchers, scholars, and practitioners.*
*Fink, A. (2005). Conducting Research Literature Reviews. London: Sage.

Level of Evidence Pyramid
Qualitative Studies

Criteria for Selecting a Resource
1. Soundness of evidence-based approach
2. Comprehensiveness and specificity
3. Ease of use
4. Availability

Questions to Ask
 Bias? Conflict of interest?
 Evidence grading or ranking applied?
 Links?
 Discipline coverage?
 Consistent and quick to search?
 Cost?
 Available in my location?

A Comprehensive Search is...
 Systematic
 Explicit
 Reproducible

7 tasks in the Research Lit Review
1. Selecting research questions
2. Selecting your sources
3. Choosing search terms
4. Running your search
5. Applying practical screening criteria
6. Applying methodological screening criteria
7. Synthesizing the results

Why do you need a research question?

Scenario
You’re applying for a grant to support your research on
management of patients with atrial fibrillation.
Think of a question related to this topic...

Possible questions
Broad:
 What is the prevalence of atrial fibrillation?
Narrow:
 What costs are associated with hospitalization for atrial fibrillation?
Very Narrow:
 What strategies have been utilized in Iran to reduce length of stay for
patients with atrial fibrillation?

How questions influence search results
Relevancy
Retrieval
(# of search
results)
Broad
Questions
Narrow
Questions
High =
lots of
articles
Low =
very
few
articles
High = directly
relevant articles
Low = mostly
irrelevant articles

Sample Search Statements
 I am looking for articles about osteoarthritis of the knee.
 13,886 articles in PubMed
 I am looking for RCTs on arthroscopic surgery for
osteoarthritis of the knee that include placebo surgery as a
control.
 9 articles in PubMed
 I am looking for RCTs on arthroscopic surgery conducted
in latino females with type 1 diabetes mellitus.
 0 articles in PubMed

Stage In Searching
1. Define search topics
2. Choose appropriate search terms/keywords that represent the
topic
3. Decide where to search/which sources to use (e.g. library
catalog, online databases)
4. Develop search strategy by optimizing search tools
5. Observe search results
6. Revise the search as necessary

Turn your statement into a strategy
1. Break you question into concepts
2. Identify subject headings for each concept
3. Identify keywords for each concept
 Tips:
 Use a “target article” to help identify search terms
 Use a strategy worksheet to keep track of your terms:
http://www.lib.uwo.ca/files/taylor/grad/Search_Strategy_Worksheet.pdf

Does hand washing prevent MRSA? in the
ICU?
Hand washing MRSA ICU Prevention
Handwashing
[MeSH]
Methicillin-Resistant
Staphylococcus
aureus [MeSH]
Intensive care units
[MeSH] +
Handwash$.mp. Methicillin resistant
staphylococcus
aureus.mp.
Intensive care
unit$.mp.
Prevent$.mp.
Hand wash.mp. MRSA.mp. ICU.mp.
Hand disinfect.mp. Critical care
unit$.mp.
Surgical scrub$.mp.
Hand clean$.mp.

Lit reviews depend on data from seven
sources
1. Online public bibliographic databases
2. Commercial bibliographic databases
3. Specialized bibliographic databases
4. Manual or “hand searches” of references lists
5. “Grey literature”
6. Web reports
7. Expert opinions

Where to search
Bibliographic Databases
 Medicine
 PubMed (or Ovid MEDLINE), EMBASE, Cochrane Library, PsycINFO
 Multidisciplinary
 Scopus
 Web of Science
 Nursing and Allied Health
 CINAHL
Websites
 Associations, Organizations & Government
 World Health Organization, Health Canada, Canadian Medical Association, etc.
Other
 “Grey Literature”
 Dissertations & Theses, SCOPUS (conference proceedings), Web search engines

Different databases have different subject
headings
 Tips:
 Select subject headings that are the closest match for your concept
 Pay attention to “explode” commands – some databases will search
related headings by default, others will not
Database Subject Headings
Medline MeSH
EMBASE EMTREE
CINAHL CINAHL Headings
Cochrane Library MeSH
PsycINFO Thesaurus of Psychological Index Terms
Scopus, Web of Science N/A

Which term explodes?
A. Bird Diseases B. Neutropenia

Identifying concepts & MeSH headings
Which concepts are contained in the question:
Does hydration decrease incidence of delirium
at the end of life?
Find the MeSH heading(s) for each concept & add them to your worksheet

AND AND
OR exp Fluid Therapy/ Delirium/ exp Terminal Care/
OR Palliative Care/
exp Terminally Ill/
OR
OR
OR
Concept #1
Ovid MEDLINE strategy
Concept #2 Concept #3
Subject
Headings
Text
Words
Blank worksheets: http://muhclibraries.mcgill.ca/SearchStrategyWorksheet.doc

Key Operators in Ovid
Operator Command Example
* Find alternate endings to this
word
nurs* [will find nurse, nursing,
nurses]
.tw. Search for this term in the Title
and Abstract fields
anxiety.tw.
adj Search for one term within x
number of terms from another
patient adj3 anxiety [will find
patient within three words of
anxiety]
AND Find articles where both terms
appear
smoking AND cessation
OR Find articles where either term
appears
smoking OR tobacco

AND AND
OR Palliative Care/
exp Terminally Ill/
OR
hydrat*.tw. deliri*.tw. (terminal* adj4 patient*).tw.
OR
fluid*.tw. palliative.tw.
OR
water.tw. end of life.tw.
Concept #1
Ovid MEDLINE strategy
Concept #2 Concept #3
Subject
Headings
Text
Words

Running your search(es)
 Start with your first concept
 Search for the subject headings first
 Then search text words
 Combine these synonymous searches with OR using your
search history
 Repeat for your second, third, and subsequent concepts
 Finally, combine large search results set with AND

Running your search(es)
Search #2 =
Search #3 =
Search #4 =
Search #5 = #1 OR #2 OR #3 OR #4
Search #1 =
Concept 1
Search #6 =
Search #7 =
Search #8 =
Search #9 =
Concept 2
Search #10 = #6 OR #7 OR #8 OR #9
Search #11 = #5 AND #10
Results

Please complete the following search in
Ovid Medline
AND AND
OR Palliative Care/
exp Terminally Ill/
OR
hydrat*.tw. deliri*.tw. (terminal* adj4 patient*).tw.
OR
fluid*.tw. palliative.tw.
OR
water.tw. end of life.tw.
Concept #1 Concept #2 Concept #3
Subject
Headings
Text
Words

APPLYING PRACTICAL SCREENING
CRITERIA

Screening
 Two kinds: practical and methodological
 Use practical screening to identify a broad range of
potentially useful studies
 Use methodological screening to identify the best available
studies

Practical Screening Criteria –examples
1. Date of publication
 only studies conducted between 2005 and 2010
2. Participants or subjects
 only children 6 to 12 years of age
3. Publication language
 only materials written in English or French
4. Research design
 only clinical trials

Apply Practical Screens
 Add the following screens (limits) to your combined search
result set:
 English Language
 Publication Year: 2001 – Current
 Humans

LIMITS/FILTERS
• Most databases offer limit functions to help users limit
search results that are too broad or too many
• Limits are commonly specified according to:
 - date of publication
 - type of publications (books, journals, news, etc)
 - age group
 - language
 - sex (male/female)
 - type of files

Working with your results
 Save or export search results into a citation manager (i.e.,
Endnote)
 Remove duplicates
 Remove inappropriate studies by applying methodological
screens

Methodological Screening Criteria - some
questions to ask
 Is the study’s research design internally & externally valid?
 Are the data sources used in the study reliable & valid?
 Are the analytic methods appropriate?
 Are the results meaningful in practical & statistical terms?*

Moving to another source
 Retain as much of your original strategy as possible
 Recognize that subject headings will be different (or non-
existent)
 Keep track of your search terms using new worksheets

Hand searching and final steps
 Locate the reference lists for selected articles*
 Identify new articles that have cited your articles*
 Identify key journals and “hand search” their issues
 Test your search strategy by checking to see if a few “target
articles” appear in the results
* Use Web of Science or Scopus

Use your results to...
1. Describe current knowledge about your research topic
2. Support the need for and significance of new research
3. Explain research findings
4. Describe the quality of a body of research*

Tips For Effective Searches
1. Plan your search – identify the words that represent the topic of
your search
2. Avoid using too broad or general terms, use specific terms
instead to get limited but relevant results.
3. Use limit/filter functions as necessary
4. Create an account. Most online databases allow you to sign up
for an account/personal folder in their database that helps you
manage searches, search results or references, set up
preferences, alerts, and many others.

Research strategy guide for finding quality,
credible sources
1. Get organized
2. Articulate your topic
3. Locate background information
4. Identify your information needs
5. List keywords and concepts for search engines and
databases
6. Consider the scope of your topic
7. Conduct your searches
8. Evaluate the information sources you found
9. Analyze and adjust your research strategy

 Basic computer skill: More than
 Windows
 Word
 PowerPoint
 Excel
 SPSS
 Adobe photoshop
 Medline search
 Endnote
Basic skills for a scientist

 Paper reading
 Critically and actively
 Ability to recognize problems in the experimental
design
 Ability to recognize key sentences

 Understanding and use of the literature
 Ability to evaluate a paper critically and accurately
 Familiarity to a broad-based, relevant and current literature
 Ability to generate useful notes while reading the literature
 Ability to generate interesting and important questions
 Ability to generate original ideas on the literature

 Experimental design
 Ability to get techniques to work predictably and reproducibly
 Ability to generate high quality data with both positive and negative
controls that can give clear cut answer to a question
 Ability to find the best available information from the best sources
 Ability to interpret fully your data, generate next question or hypothesis
and design the next experiment
 Ability to troubleshoot and solve a technical problem
 Resistance to doing an incomplete experiment using whatever reagents
or cells that happen to be available ”to see what happens”

 Paper writing
 Ability to group data in a logical fashion into good figures
 Ability to make a good-looking figure
 Ability to interpret data in relation to existing literature and
come up with new ideas
 Ability to write a good and useful first draft
 Ability to use key sentence

Databases
All EBM Reviews (OVID) MD Consult
Biological Abstract Nursing Consult
CINAHL with Full text Nursing Index
Cochrane Library OVID Databases
Drug Information Full Text OVID Medline
EndNote Web Scopus
Essential Science Indicators (ESI) UpToDate
Journal Citation Reports (JCR) Ulrichsweb
Library, Information Science &
Technology Abstracts (LISTA)
Web of Science

Journals Collection
Ebsco MD Consult
Elsevier (Sciencedirect) MEDLIB
Emerald Oxford journals
Iran Medex OVID Journals
JAMA Journals Proquest
Wiley Springer
Magiran Thieme Medical Journals

MeSH (Medical Subject Headings)

Result, PMID, Related Articles!

Useful Sites
 CADTH. Grey Matters: a practical search tool for
evidence-based medicine -
http://cadth.ca/en/resources/grey-matters
 Cochrane Handbook for Systematic Reviews and
Interventions - http://www.cochrane-handbook.org/
 IOM (Institute of Medicine). Finding what works in health
care: standards for systematic reviews -
http://www.iom.edu/Reports/2011/Finding-What-Works-in-
Health-Care-Standards-for-Systematic-Reviews.aspx

Recap
 How would you describe a quality literature review?
 Synonymous searches are combined with ___
 Can you apply methodological screens with a database?
 Finally, please make your librarian happy by filling out your

EFFECTIVE MEDICAL
LITERATURE
SEARCHING

Objectives
1. Formulate your question
2. Understand basic database structure
3. Use of Boolean Logic
4. Use Field Searching
5. Use of Controlled Vocabulary
6. Specialty techniques (truncation, etc.)
7. Building your search strategy

Reasons for Searching the Medical
Literature
 To answer a specific patient case-related
question (clinical practice)
 To learn more about a medical topic
(education)
 To determine current best practice (guideline)
To give the best possible care to patients using
evidence-based medicine

Information Overload
PubMed (Medline)
contains over 18
million journal
citations going
back to ~1950
Year # new
citations
added*
2005 606,000
2006 623,089
2007 670,943
2008 671,904
*statistics from http://www.nlm.nih.gov/bsd/bsd_key.html

Asking the Question: PICO
 Patient, Population or Problem
 What are the characteristics of the patient or population?
 What is the condition or disease you are interested in?
 Intervention or exposure
 What do you want to do with this patient (e.g. treat, diagnose,
observe)?
 Comparison
 What is the alternative to the intervention (e.g. placebo,
different drug, surgery)?
 Outcome
 What are the relevant outcomes (e.g. morbidity, death,
complications)?
http://healthlinks.washington.edu/ebp/pico.html

Parsing the Question
 What are the main concepts in your question?
Sample question:
Does nutrition therapy improve decubitus
(pressure) ulcer healing in an elderly patient?
Concepts:
Nutrition therapy Decubitus/pressure ulcers
Ulcer healing Elderly patients
Treatment
efficacy

A database is an organized
collection of data.
 Bibliographic databases are searched through
many of the same techniques as any other
database
 Focus will be on PubMed, but these techniques
apply to ANY literature database

Examples of Records and Fields
Record # Author Title Publisher Date of
Publication
1 Jones KM Infectious
Diseases
Wiley 2001
2 Smith BR Medicine Cambridge
Univ. Press
2004
3 Johnson
AS
Cancer Elsevier 2005
4 Bradley PL Asthma Synergy 2003

Examples of Records and Fields
Record # Author Title Publisher Date of
Publication
1 Jones KM Infectious
Diseases
Wiley 2001
2 Smith BR Medicine Cambridge
Univ. Press
2004
3 Johnson
AS
Cancer Elsevier 2005
4 Bradley PL Asthma Synergy 2003
RED=RECORD BLUE=FIELD PURPLE = ONE PIECE OF DATA

Searching a Database
Different search interfaces do the same things in slightly different ways
Good search interfaces should provide
 Ability to search for a specific item
 Ability to search for related items to a known item
 Ability to search in a specific field or fields
 Ability to combine search terms using Boolean
Logic
 Ability to retrieve search results in a useful way

Boolean Logic
A British mathematician named George Boole
(1815-1864) developed an algebraic system of
logic that is now widely used in computer and
electronic systems including database
searching.
While Boole’s algebraic system can be complex, a
very simple form of Boolean Logic is used for
searching most bibliographic databases.

Boolean Operators
Standard Boolean Logic for database searching
uses 3 relationships among search terms.
AND
OR
NOT
It is both simple and powerful.

AND
BOTH terms included in any
results.
If a record has only one of
the two terms, it will not be
retrieved.
If the record has neither term,
it will not be retrieved.
What does this do to the
amount of records
retrieved?

OR
Only one (NOT both) of
the terms are in the
results
‘OR’ will retrieve the
record if both are
included.
What does OR do to the
amount of records
retrieved?

NOT
Excludes any results
containing the term
Records containing
both will not be
retrieved.
What does NOT do to
the amount of
records retrieved?

Using OR
“OR” groupings contain terms for the same
idea/concept and are usually put in parenthesis
(term OR term OR term)
where all terms are difference ways of
representing the same concept
(faculty OR teachers OR professors)
(students OR learners OR pupils)

Using AND
“AND” groupings contain terms for different
ideas/concepts and can combine OR groupings
Term AND (Term OR Term) where each
represents a different concept
heart attack AND smoking
Diabetes AND exercise
Cancer AND (treatment OR therapy)

Using NOT
“NOT” statements are usually put last and can
contain an “OR” grouping; they are often used
to get rid of a common subgroup
Students NOT dental
Diabetes NOT juvenile

Putting Them Together
1. Identify the concepts (Parse the question)
2. List specific terms for each concept
3. Put the terms for each concept in an OR
statements within parentheses
4. Combine OR statements with AND
5. Add any NOT statements to the end

Creating a Boolean Search
Concept 1
Influenza
Concept 2
Vitamin C
Concept 3
Treatment
Concept 4
helpfulness
Influenza Vitamin C Treatment Outcome
Flu Ascorbic acid Therapy Recovery
Orange Juice Management Success
QUESTION: Is Vitamin C helpful in treating the flu?
1. Identify concepts and list terms

Step 2
2. Make your OR statements, one per concept
 (influenza OR flu OR orthomyxovirus)
 (vitamin C OR ascorbic acid OR ascorbate)
 (treatment OR therapy OR management)
 (outcome OR recovery OR success)

Steps 3 and 4
3. Put “AND” between each of the OR statements
(influenza OR flu) AND (vitamin C OR ascorbic
acid OR orange juice) AND (treatment OR
therapy OR management) AND (outcome OR
recovery OR success)
4. Consider any NOT statements you might want
to add.
Note: NOT isn’t used very often

Parsing a Boolean Search
(emergency OR acute OR critical) AND
(treatment OR therapy OR management OR
care) AND (motor vehicle accident OR car
crash) NOT (pedestrian OR walking)
What are the four concepts?
What terms are used for each concept?
Which three concepts must be included in all records
found?
Which concept must not be included in any record found?

Beyond Basic Boolean
 Field Searching
 Controlled Vocabulary
 Subject vs. Keyword Searching
 Specialty Features
 Truncation
 Phrase searching

Field Searching
Almost all databases will provide you with some
ability to search a specific field or fields.
 Allows faster searching
 Allows more accurate searching
Not all databases may make all fields searchable.
Each search system will require a specific format.

All Field vs. Specific Field
Searches
I would like to find articles by John Smith.
 Search all fields: John Smith
 Search Author Field only: John Smith
I would like to find an article published in 1997.
 Search all fields: 1997
 Search Publication Date Field: 1997
Why waste time searching for a date in the author field or
an author in the volume field?

Formats for Field Searching
Different databases provide different formats for
specifying fields.
Most use field names or nicknames
 Field ‘tags’ OR ‘labels’
which may follow a period or be placed in brackets
or parentheses.
Some databases offer forms or drop-down menus.

PubMed
Field tags go in [] and follow term
Field tags can be used within Boolean queries

PubMed Field Tags
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hel
ppubmed.section.pubmedhelp.Search_Field_D
escrip
[au] = author
[ti] = title
[tw] = textword
[tiab] = title and abstract
[mh] = medical subject
heading
[dp] = date of publication
[la] = language
[gr] = grant number
[ta] = journal name
[ad] = affiliation

OVID databases require field tags to follow the
term separated by a period.
Meharry.in and 2005.yr

Some databases, such as the ISI’s Web of
Science (Science Citation Index Expanded)
provide forms to fill out.
Select Field
from drop-
down menuSelect
Boolean
Operator

Combining Field Searches
Multiple field searches can be combined using
Boolean logic.
Find a 2005 article by an author named Hubble
about ankle fractures.
Combine with AND:
 2005 in date/year field
 Hubble in author field
 Ankle fractures in title field
2005[dp] AND Hubble[au] AND ankle fractures[ti]

Final Notes on Fields
 Each database provides its own specific fields
 Each database requires a specific format to
designate field searching
 When searching a new database, take a
moment to read the help documentation; most
will provide a list of fields and how to search
them.

Controlled Vocabulary
A controlled vocabulary is a set of established
terms where
 every term represents a single concept
 only one term is used for that concept

Another example
 How many words could you think of for the idea
of “cancer”?
 Cancer, tumor, malignancy, neoplasm, sarcoma…
 Articles in a database
 Article one: “Breast tumors in young women”
 Article two: “Surgery for prostrate cancer.”
 Article three: “Diagnosing Melanoma.”
All three articles are about types of cancer but
different terms are used in titles.

In a controlled vocabulary ONE word (i.e., cancer) is
chosen and placed in a special field, usually called a
subject field.
For all three articles
 Article one: “Breast tumors in young women”
 Article two: “Surgery for prostrate cancer.”
 Article three: “Diagnosing Melanoma.”
The subject term (concept term) “cancer” is placed in the
subject field by database indexers.
Now, Searching the database for cancer in the subject field
will identify all records about the concept of cancer even
if a different word for cancer is used.
 Search ‘cancer-in-subject-field’ finds all three articles
 How many articles would the search ‘cancer-in-title-field’
find?

Structure of Controlled Vocabulary
Broader
Concepts
Narrower
Concepts

More on Controlled Vocabulary
 “Expanding” = Search includes all narrower
terms beneath the searched term
 Some databases do it automatically, others don’t
 “Focusing” or “Majoring” = For a given item,
some subject terms are considered the major
focus; you can select to return only those
articles.
 Hip fracture[majr] = only give me articles where hip
fracture is an important concept

Subject vs. Keyword Searching
Controlled vocabulary
searching
 Matches terms against a
specific field in the record.
 You need to consult a
thesaurus (paper or online)
to find out what the
controlled vocabulary term
is for each concept.
Free-text (keyword)
searching
 Some concepts have many
synonyms. A free-text search
statement would mean
"OR"ing all those terms
together
 Matches terms against words
anywhere in record (abstract,
title, etc.).

Advantages to Controlled
Vocabularies
 Using the controlled vocabulary can make your search
more precise and easier.
 Increases the relevancy of results (fewer false drops)
 The indexers have already done much of the work for
you.
 Searchable tree structures of terms can help you find
new terms to use.

Problems with Controlled
Vocabularies
 NOT all databases use a controlled vocabulary
 New concepts take time to be added
 There is often a lag phase during which the
newest articles aren’t indexed
 Controlled vocabularies can contain some very
strange things and some concepts may not be
handled well
 The controlled vocabulary must be easily
searchable
Trying to understand what is and isn’t in a
particular controlled vocabulary can give you a
big headache!

Combining Subject and Keyword
Searching
To be comprehensive, it is often helpful to combine
subject and keyword searching
(diabetes mellitus[mh] OR diabetes[tw])
(sickle cell anemia[mh] OR sickle cell anaemia[ti])

Don’t forget…
 Boolean logic to combine terms
 Use of other search fields in combination with
subject terms
A Complex Search:
(head[mh] OR head[tw]) AND (wound and
injuries[mh] OR trauma[ti] OR injury[ti]) AND
2005[dp] AND English[la]

Some Specialty Features
 Truncation
 Phrase searching
 Neighboring and other rarer Boolean operators

Truncation
What about including the singular and plural versions of words
as well as other word variations?
For example: therapy, therapies, therapeutics,
You could combine them all in an OR relationship:
(therapy OR therapies OR therapeutics OR therapeutic)
But an easier way is by the use of truncation.
therap*
Each database handles truncation in a unique way.
The ‘*’ and ‘$’ are the most common wildcard symbols.

More on Truncation
Some examples:
Bacter$
Proc*
Vir?
Staph?
Be cautious when truncating!
If the word stem is too short, there may be too many
possible variations and you might pick up unrelated
terms.
For example, using proc* for finding procaine-like drugs will
also include words like proceedings and process.

Phrase Searching
 Sometimes you want to force the database to
search for a set of words in exact order
“fever of unknown origin”
Most databases will accept a phrase in quotes.
BUT…some do not handle phrases well and will
automatically break them up – usually ‘AND’-ing
the terms
Check how the database handles phrase
searching before doing it!

Limits Options
 Many databases provide “limits” pages that
make it easier for you to select common
options such as language, article type,
publication dates, human or animal, gender,
age groups, etc.
 Each database’s limits options are unique
 Most limits can be done ‘by hand’ using field
tags, but sometimes limit pages save time

Step-By-Step Search Construction
1. State the question
2. Identify the concepts in the question
3. For each concept, determine keywords and subject
terms
4. Specify field tags after terms if needed
5. Combine terms for the same concept with “OR” in
parenthesis
6. Combine “OR” statements with AND
7. Put any NOT terms at the end
Keep track of your searches, how many articles were
found total, and how many you selected as relevant

Example
 Question: What is the appropriate ED medical
management of adult patients with intracranial
hemorrhage (either trauma or spontaneous)?

How to Conduct a Literature Review (ISRAPM 2014)

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