Literature search techniques

1. LITERATURE SEARCH
STRATEGIES
Hajer Elkout

2. Purpose of a Literature Search
• Broadens your knowledge on a topic.
• Shows your skill at finding relevant information.
• Allows for critical appraisal of research.

3. How to start?
• There are many ways to begin literature search, generally
we have:
• Keywords (most commonly used)
• Begin from a paper given by your mentor
• References from a given paper
• Journals in your interest of subject areas
• Authors, if you know some …
• In other words….Adapt a search strategy!!
• PLAN
• PLAN
• PLAN

6. 9. Appraise

8. Steps for effective search strategy
• Defining your topic.
• Turning our topic into a question.
• Choosing your search terms.
• keywords for each of the concepts in the question.
• Which databases should I search?
• Compiling the search and running it in a database.
• Evaluate.

9. Define the topic/the question
• What am I looking for exactly? Question before you
search!
• Test search to find out how much information is available.
• If you are finding little information - broaden the question.
• If you are finding lots of information - narrow the question.

10. Keywords for the concepts in the question
• Break the question down into the main concepts.
• Use all possible acronyms or synonyms.
• Keep in mind that names change (Mongolism or down's
syndrome).
• US/UK spelling variations.
• Databases will search for the term you have typed in,
including any spelling mistakes!

11. Break the question down into the main concepts
Which are the most effective ways to deliver maternity services to
rural populations in low-income countries?
Maternity Services
• Maternal health service(s)
• Maternal healthcare
• Maternal health care
• Maternal service(s)
• Maternity care
• Maternity service(s)
• Postpartum
care/service(s)
• Postnatal care/service(s)
• Prenatal care/service(s)
• Antenatal care/service(s)
Rural populations
• Rural community/ties
• Rural population(s)
• Remote population(s)
• Remote
community/ties
• Non-urban
• Villages
Low income
countries
• Developing
country/countries
• Developing nation(s)
• Developing world
• Low resource setting
• LMIC(s)
• Africa(n)
• South East Asia(n)
• South America(n)

12. Keywords…

13. Concepts and keywords
Concept Key words
Thrombosis Thrombosis, DVT, Leg thrombosis,
Thrombus, Thrombotic, Thrombolic
Thromboembolism, Thrombosis

17. Boolean example AND results

18. AND 3 terms results

19. You can run your search as one long search string,
using brackets/parenthesis to separate the concepts…
• ("maternity services" OR "maternal health services" OR
"postnatal care" OR "postpartum care") AND ("rural
populations" OR "remote populations" OR "rural
communities" OR "remote communities" OR non-urban
OR villages) AND ("developing country” OR "low income
country" OR Africa OR "south America" OR "south east
Asia")

20. Or you can search for each concept separately, and
then combine the individual searches together with
AND at the end.
1. (matern* OR postnatal OR postpartum OR prenatal)
and (care OR service*).
2. rural communit* OR remote communit* OR rural
population* OR remote population* OR village* OR
non-urban.
3. developing countr* OR low-income OR africa* OR
south america* OR south east asia*
4. 1 AND 2 AND 3.

21. Use Search History to combine your search
results
The total records
found

23. Internet Search tools
• Which search tools are needed?
– Gateways.
– Search Engines.
– Databases.

24. Gateway/web portal
• A webpage designed to attract visitors and search
engines to a website on a specific topic(s).
• Organize information in a structured way in general
or subject categories.
• Examples:
– WHO A-Z health topics list
www.who.int/topics/en/
– Essential Health Links
www.healthnet.org/essential-links/

25. Search results on Google
This is how Google presents the results
of your search. Follow the links to the
websites you wish to visit.

26. Search Engine
• A program that searches documents for
specified keywords and returns a list of
documents where the keywords were found.
• Examples
• Google www.google.com
• Google Scholar (more academic)
www.scholar.google.com
• Yahoo www.yahoo.com

27. When to use search engines
• For general information.
• When topic has many facets.
• For current information.
• For single article search.

28. Note the various options for refining
a search including Reading level,
Results per page, Language and
File Type.

29. Google Scholar provides a simple way to broadly
search for scholarly literature. You can search across
many disciplines and sources: peer-reviewed papers,
theses, books, abstracts and articles, from academic
publishers, professional societies, preprint repositories,
universities and other scholarly organisations.

30. Title links to
abstract and
possible source
of full text
“Find it with
OLinks” links to
full text version
Link to articles
that cited the
work
Link to related
articles

31. Note the various options for refining a
search and also that you can change
the number of results per page.

32. Google
Advantages
• Searches articles,
books and webpages.
• Has advanced search
options.
• Can limit search by
dates, document types,
language, domain and
more…
Disadvantages
• No indexing terms
• Huge retrieval of almost any
topic.
• No ability to select citations for
downloading or printing.
• Built in relevancy ranking
based on times cited.
• Cannot limit to journal articles.

33. Google Scholar (search engine)
Advantages
• Searches journals, books
and more academic
sources.
• Can download individual
citations into bibliographic
managers.
• Contains citing information
with links to sources citing a
specific term.
Disadvantages
• No indexing terms.
• Huge retrieval of almost any
topic.
• No ability to select citations
for downloading or printing.
• Built in relevancy ranking
based on times cited…
• May result in bias toward
older literature.

34. Database
• A collection of information organised in such a way that a
computer can quickly select desired pieces of data.
• An electronic filing system.
• Traditional databases are organised by fields, records
and files.

35. • Cochrane Library (Systematic reviews and review protocols)
• http://www.cochrane.org/
• TRIP (Turning Research Into Practice- Evidence based healthcare
database)
• http://www.tripdatabase.com/index.htm
• NIHS (National Institute for Health Research)
• http://public.ukcrn.org.uk/search/.
• PubMed (biomedical literature from MEDLINE and other life science
journals)
• http://www.ncbi.nlm.nih.gov/pubmed/
• Bandolier (Evidence based healthcare database)
• http://www.medicine.ox.ac.uk/bandolier/
• National Guideline Clearing House (resource for evidence-based
clinical practice guidelines)
• http://www.guideline.gov/
• Effective Health Care
• http://www.york.ac.uk/inst/crd/ehcb.htm

36. • The following databases are accessed through institutions
(they have to purchase licenses to have access to these),
and contain evidence based healthcare articles from a
variety of health professions.
• MEDLINE
• http://www.ebscohost.com/nursing/products/medline-databases
• CINAHL
• http://www.ebscohost.com/cinahl/
• Embase
• http://www.elsevier.com/online-tools/embase

37. Medline Medical LiteratureAnalysis and Retrieval
System Online
• Medline is the electronic database of indexed citations and
abstracts of the US National Library of Medicine (NLM).
• It includes bibliographic information for articles and
abstracts covering medicine, nursing, pharmacy, dentistry,
veterinary medicine, and health care, and preclinical
sciences journal articles.
• It contains >21 million records from approximately 5,000
selected publications from 1950 to the present.

38. EMBASE Excerpta Medica Database
• Produced by Elsevier science.
• > 24 million indexed records and > 7,600 indexed peer-
reviewed journals.
• 1974 to present.
• Includes ≈ 30% of Medline records.
• > European emphasis vs Pubmed.
• Useful to search for non English language publications.

39. EMBASE Excerpta Medica Database
• Core strengths:
• Coverage and in-depth indexing of the drug-related clinical
literature, with a particular focus on adverse drug reactions.
• Emphasis on evidence based medicine (EBM) indexing including
systematic reviews.
• Coverage and indexing of journals and articles relevant to the
development and use of medical devices.

40. WEB OF SCIENCE
• Online academic citation index provided by Thomson
Reuters®.
• Provides access to 6 electronic databases.
• Has indexing coverage from the year 1900 to present.
• Encompasses 11,261 journals selected on the basis of
impact evaluations and 46.1 million records (incl. conference
proceedings).
• All titles are translated in English.

41. Cochrane library
• Important for clinical searches and especially for clinical
trials or systematic reviews.
• The core is the database of systematic reviews.
• Includes also the Cochrane central register of controlled
Trials and the Cochrane methodology register.

42. CINAHL Cumulative Index to Nursing and
Allied Health Literature
• Most important database for nursing sciences.
• includes more than 5000 journals dating back to the
1930s and has more than 3.2 million citations.
• Includes book chapters, audiovisuals, softwares,
dissertations and conference proceedings.
•
• Emphasis also on biomedicine, behavioral sciences,
education, etc...
• No free version.

43. CINAHL
Advantages
• Well indexed and can
'explode' terms.
• Very current.
• Many ways of sorting
retrieval.
• Can select citations to
download or print.
Disadvantages
• Access limited to nursing
and allied health
materials that are
indexed in the database.
• Does not search full-text
for most items.

44. OVID
• Commercial organization (Ovid Technologies) that
provide access to several bibliographic databases,
including Medline and Embase.
• The database is available to you depends on the
subscriber.
• Less user friendly than Pubmed, but allows complex
searches.

45. PubMed
• PubMed is a service of the US National Library of Medicine
(NLM) at the National Institute of Health (NIH).
• It was developed in 1996 by the National Center for
Biotechnology Information (NCBI) at the National Library of
Medicine.
• 22 million citations from more than 5400 journals dating back
to the 1940s.
• Provides free access to MEDLINE.
• Includes additional selected life sciences journals not in
MEDLINE.

46. PubMed
Advantages
• Well indexed using Medical
Subject Headings (MeSH).
• Includes citations of e-journals
prior to publication.
• Can download info to
bibliographic managers.
• Can select citations to
download or print.
Disadvantages
• Access limited almost
exclusively to basic and
health sciences journals
that are indexed in the
database.
• Does not search full-text of
articles.

47. Beyond databases
• References in good articles.
• Hand searching journals.
• Clinical trials (clinicaltrials.gov).
• Contact authors to identify additional unpublished work.

48. Search: Asthma in Pregnancy
(performed 03 December 2009)
• Google: 11,800,000
citations; first citation
– October 2005;
www.emedicine.com
• Google Scholar:
79,000 citations; first
citation – December
2000; American
Journal of Medicine
(first 2009 citation is
18th)
• PubMed: 2076; first
citation – December
2009; Obstetrics and
Gynecology
• CINAHL: 567 in basic
search; 467 in
advanced search; first
citation – November
2009; Journal of
Pediatrics
Judkins, So You Want to use Google… MLANEWS, February 2010

49. Example (Steps 1-4)
1. Ask: What health problems are associated with water pollution?
2. Main Concepts: health, water, pollution
3. Need: scholarly primary research
4. Select terms:
– Broader terms: ‘health’, environmental degradation’,
‘agricultural management’,
– Synonyms:
health, illness, disease, etc.
water, rivers, lakes, sea, domestic water, etc.
pollution, ‘oil spills’, chemical, biological, toxicity, etc
– Alternative spellings: none
– Plurals: river(s), lake(s), disease(s)
– Capitals: e.g. name of a specific lake, disease, region

50. Conduct the search
• Use your key words and Boolean Operators.
• Use truncation symbols.
• typing learn* into the Cochrane Library database would find learn,
learns, learner, learners, learning
• Wildcard may be used to search for alternative spellings
or forms (?, #. !)
• typing organi?ation into the Cochrane Library database would find
both organisation and organization
• typing wom?n into the Cochrane Library database would find both
women or woman

51. Truncation and wildcards
• Truncation allows you to search for variant forms of a
word as a single search concept.
• By adding/replacing characters at the end, beginning, or
middle of the word with a truncation symbol, also known
as a ‘wildcard.’
• Common truncation symbols include the *, #, $, and ?.

52. Beware of early truncation…

53. Utilise database features
• Search fields:

54. • Apply filters:

55. • Limits:

56. Other Features
• Search within results.
• Related articles and links.
• Check Search tips or search help in different databases…
• Basic search.
• Advanced search (multiple search terms in multiple fields).
• Search history.

57. How to use PubMed?
Interactive tutorials for training

58. PubMed Basic subject search
Use Boolean operators (AND – OR – NOT)

59. • Use MeSH headings
• MeSH headings are Medical Subject Headings
How to improve the accuracy of your
Pubmed search

60. The MeSH controlled vocabulary is a distinctive feature. Of Pub Med
It imposes uniformity and consistency to the indexing of biomedical literature.
MeSH terms are arranged in a hierarchical categorised manner called MeSH
Tree Structures and are updated annually
 25000
MeSH
headings

61. Set up your limits/filters

62. Set up your limits/filters

63. Use PubMed advanced search builder

64. When you are happy with your search…

65. When you are happy with your search…
• Save this file as a .txt file to your hard drive
• This allows for future editing

66. The clipboard will hold the articles on your PC for 8 hours.
At the end, click on Clipboard to collect your articles
Save your searches on the CLIPBOARD

67. Save searches on the My NCBI Save search feature

68. PubMed creates this set by comparing words
from the title, abstract, and MeSH terms using a
powerful word-weighted algorithm.
Citations are displayed in rank order from most
to least relevant.
Use the RELATED ARTICLES feature

69. Store your bibliography in a Reference Manager
software
EndNote ®
Reference manager ®

70. Free Full Text
Look for FREE FULL TEXTARTICLES
1
3
2

71. Example*
• Case 1
A 50-year old male with new onset type II diabetes consults you for lipid
management. Patient has an LDL Cholesterol of 96 mg/dl with HDL
Cholesterol of 48 mg/ dl. He recently heard that diabetic patients with
even low LDL cholesterol might derive benefit from the use of statin
.
• Your question is:
Do patients with diabetes and low LDL cholesterol (P) have better
outcomes (O) if they are treated with a statin medication (I)
compared to no treatment (C)?
* Sood and Ghosh. Literature Search Using PubMed: An Essential Tool for
Practicing Evidence- Based Medicine. JAPI. 2006:54:303-308

72. Literature search, PubMed
• Type in the search term, “diabetes AND low LDL AND
treatment”.
• Look at the search results.
• You retrieve over one thousand citations.
• Select ‘Limits’ and make the following selections:
• Publication types - Randomized controlled trials
• Ages – All Adult: 18+ years
• Publication Date – From 2002 To 2004
• Subsets – Core clinical journals (Core Clinical Journals is a list of
120 clinical journals that are likely to be available at most medical
school libraries).
• You have much fewer articles that are more relevant.

73. Example 2
• In patients with sepsis (P), does treatment with steroids (I),
compared with no steroids (C), alter mortality (O)?
• adult human or any patients.
• septic shock or severe sepsis.
• Steroids or Methylprednisolone.
• Modifications of the concepts leads to a different question:
• In patients with septic shock, does treatment with steroids,
compared with no steroids, alter outcome as reflected by mortality?
• In adult human patients with severe sepsis, does treatment with
methlyprednisolone, compared with no methlyprednisolone, alter
outcome as reflected by mortality?

74. A different example*
• CASE 5
You are an expert on the drug therapy of pulmonary tuberculosis.
You would like to remain current with the literature on this topic.
• Select the ‘Cubby’ feature from the ‘Side bar’.
• Set up your own ‘Cubby’ account.
• Now go back to PubMed homepage and enter the search
term “pulmonary tuberculosis AND drug treatment” in the
‘Query box’.
* Sood and Ghosh. Literature Search Using PubMed: An Essential Tool for
Practicing Evidence- Based Medicine. JAPI. 2006:54:303-308

75. • Log on to your ‘Cubby’ account. Your search term is
present in the ‘Cubby Search Name’ box.
• Select ‘Store in Cubby’.
• The search is stored in your ‘Cubby’ account. The date
and time the search was performed is also stored.
• Re-access your ‘Cubby’ account a few days from your first
search.
• Select the search by checking the box to the left of it.
• Now select the option ‘What’s New for Selected’.
• The output would comprise of citations added to PubMed since
your last search.

76. Evaluate/Revise
Review and refine you search
• Be prepared to review/revise your search.
• Keep your search terms in concept.
• Sets/zones but remember to explore subtopics.
• Try new sources of information.
• Save the search and citations for future use.
• Promote use of high-quality resources.

77. Manage Results
• Download, print, save, e-mail results and search
History.
• Cite using a biomedical citation style.
• Save search, set up alerts.

78. Evaluate-Who? What? When? Where? Why?
• Does the paper cover the correct topic? Is it relevant to my
patient(s)?
• You are guaranteed to find at least one totally irrelevant paper in every
search you do.
• Is the information recent enough?
• did you specify a date range?
• Does it match the type of information you wanted
• Qualitative, quantitative, research design?
• Is the study significant?
• Strengths and weaknesses.
• If you found relevant articles – congratulations!

79. Finally…
Apply–Answer the question.

81. Issues…
• Problem 1 – I can’t find any papers
• Check your spelling
• Are you searching the most relevant database?
• Have you tried using truncation or wildcards to capture all forms of
your keyword?
• Problem 2 – I have too many irrelevant papers
• Check your search terms, are they specific to the information you
want to find?
• Add limits to your search, i.e.: limit to a particular language, years
of publication or peer reviewed only.

82. Important notes
1. You need to accept your search and be realistic.
your “ideal” search, even if conducted correctly, may miss a few papers
that will be relevant to the topic.
2. Pre-defined criteria and specific research question.
decide on research design, populations, outcomes, timeframes,
comparators etc. before you start to search for papers.
make sure you have a very clear question you want to answer.
3. There is no magic number to make a ‘manageable’
result list.
each search will be different, some topics will have huge amounts of
articles relating to them, others not.

83. • The overall goal is to locate all published studies relevant to
key questions.
• A balance must be achieved between recall and precision:
• Recall = how much of the relevant literature is retrieved.
• Precision = how much of the retrieved literature is relevant.
• An optimal balance depends on the context. The target is to
conduct a comprehensive and thorough search while
minimising the resources needed to review retrieved
citations.

84. Last note to take …
• Effective literature search really depends on many
factors, some of which are:
• How much you have known a subject.
• Your research experience.
• Guidance from mentors.
• Your library resources … access to the right literature, etc
And …

85. The literature searching process
“is not an exact science but an art.”
Samuel Butler
Try to think of the process as a
“journey not a destination”
Hearst

86. Research with the
Internet

87. How To Tell the Good from the Bad
• Web site evaluation criteria:
• Who runs the site?
• Who pays for the site?
• What is the purpose of the site?
• Where does the information come from?
• What is the basis of the information?
• How is the information selected?
• How current is the information?
• How does the site choose links to other sites?
• What information about you does the site collect, and why?
• How does the site manage interactions with visitors?
”Ten Things to Know about Evaluating Medical Resources on the Web,” National Cancer
Institute, http://www.cancer.gov/cancerinfo/ten-things-to-know

88. The Criteria
1. Who runs the site?
• Eg. – MEDLINEplus - http://medlineplus.gov
• Header on all MEDLINEplus pages
• “A service of the U.S. National Library of Medicine and the National
Institutes of Health.”
• Footer
• Links to both organisations are located at the bottom of each page.

89. The Criteria
2. Who pays for the site?
• The URL ends in .gov which indicates that the site is
sponsored by the government.
• Some other kinds of sites:
.com indicates a corporate site, e.g. http://www.merck.com
.edu indicates a site affiliated with an educational institution,
e.g. http://www.harvard.edu
.org indicates a non-profit organisation’s website,
e.g. http://www.americanheart.org

90. The Criteria
3. What is the purpose of the site?
• “MEDLINEplus is designed to help you find appropriate,
authoritative health information.”
http://www.nlm.nih.gov/medlineplus/criteria.html

91. The Criteria
4. Where does the information come from?
• NLM
• NIH
• ADAM (Encyclopedia)
• Merriam-Webster (Dictionary)
• News (Reuters)
• Various health organisations & their websites

92. The Criteria
5. What is the basis of the information?
• Varies by link
• Research links sections tend to have more evidence based
links
• e.g. of evidence:
• http://cis.nci.nih.gov/fact/5_6.htm
• http://www.marchofdimes.com/professionals/681_1189.asp

93. The Criteria
6. How is the information selected?
http://www.nlm.nih.gov/medlineplus/criteria.html
• The site mainly uses full-text publications produced by the NIH
and other federal government organizations
• External links are also chosen based on criteria listed under
“selection criteria” (see criteria #8).

94. The Criteria
7. How current is the information?
• MEDLINEplus pages list last updated date at bottom.
• Most pages have been reviewed or updated within the last 2-3
years.
• e.g. http://www.nlm.nih.gov/medlineplus/antioxidants.html

95. The Criteria
8. How does the site choose links to other sites?
• MEDLINEplus -
http://www.nlm.nih.gov/medlineplus/criteria.html
• Their criteria:
• Quality, authority and accuracy of content.
• Purpose of site is educational, not selling a product and offers information free
of charge.
• Availability and maintenance of the web page.
• Special features.

96. The Criteria
9. What information about you does the site collect,
and why?
• e.g. MEDLINEplus -
http://www.nlm.nih.gov/medlineplus/privacy.html
• Privacy Statement located in the Privacy link at the bottom of
each page. It states that they collect the following information:
• IP address from which you access the Internet
• Date and time you viewed their page or pages
• Internet address of the Web site from which you linked
directly to their site
• Name of the file or the words you searched
• Browser used to access their site.
• Any information you personally provide to them.

97. The Criteria
10. How does the site manage interactions with
visitors?
• e.g. MEDLINEplus - http://medlineplus.gov
• “Contact Us” button top of pages in the header.
• Email form to be filled out by the user.
• No personal information is required.
• Only ask for an email address if you want a reply.
• The direct email address is also provided in case the form does
not work.