This document provides guidance on searching the medical literature. It discusses four categories of information resources, criteria for selecting resources, and five databases for finding primary studies. It outlines how to develop a search strategy, including turning a question into search concepts and keywords. It also covers running searches, applying screening criteria to search results, and synthesizing findings. The goal is to perform a systematic, explicit and reproducible search of the biomedical literature.

1. Searching the Medical Literature
Robin Featherstone
Clinical Medicine Librarian
UWO
rfeathe@uwo.ca
http://www.slideshare.net/featherr
Selinda Berg
Clinical Medicine Librarian
Windsor
sberg@uwindsor.ca

2. 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

3. Level of Evidence Pyramid
Qualitative Studies

4. Systems, Synopses & Summaries
Systems Synopses Summaries
Few exist Number in the thousands Fewer than 50,000
Textbook-like; integrate
clinical evidence with other
types of info; directed at
clinical practice decisions
Summaries of studies and
systematic reviews;
includes guides or advice
from expert clinicians
Systematic reviews of
articles and guidelines; you
assess and make decisions
Very easy to use Easy to use May require searching

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

6. 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?

7. Studies
• Number in the millions
• No processing of evidence – must individually
assess
• Require searching large databases

8. Available from Western Libraries (or for free)
Systems Synopses Syntheses Studies
• ACP PIER
• DynaMed
• Clinical Evidence
• UpToDate
• Micromedex
• ACP Journal Club
• InfoPOEMS
(Essential Evidence
Plus)
• DARE (Database of
Reviews of Effects)
Centre for
Reviews and
Dissemination
• Cochrane
Database of
Systematic Reviews
 Cochrane
Library
• US National
Guidelines
Clearinghouse
• MEDLINE
 PubMed
 Ovid
 Pubget
• EMBASE
• SCOPUS
• Cochrane
Controlled Trials
Registry (CCTR)
 Cochrane
Library
• CINAHL
• PsycINFO
• Web of Science
•TRIP Database
Find at: www.lib.uwo.ca/programs/undergraduatemedicaleducation/

9. HOW TO SEARCH STUDIES

10. A Comprehensive Search is...
• Systematic
• Explicit
• Reproducible

11. 7 tasks in a comprehensive search
1. Develop a search statement or question
2. Select a source
3. Choose search terms
4. Run the search
5. Apply practical screens (limits)
6. Apply methodological screens
7. Synthesize the results

12. 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

13. 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

14. 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.pd
f

15. 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.

16. Different databases have different
subject headings
• Tips:
– Complete a concept map for each database that you search
– Select subject headings that are the closest match for your
concept (remember: systematic, explicit and reproducible)
– 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
Web of Science N/A
Scopus N/A

17. Some key operators in Ovid
Operator Command
$ Truncation (finds alternate endings)
? Wildcard (finds alternate spellings)
.mp. Mapping Alias (tells Ovid to search for your term in the Title,
Abstract, Subject Headings, Table of Contents and Key Phrase
Identifier fields) – useful for lit. reviews because it is broad
() Parentheses control the order of search operations
Adj Adjacency operator (can be followed by a number) tells Ovid
terms must appear adjacent to one another
AND all terms must appear in results
OR any terms will appear in results
Note: These are recommended operators for research lit reviews. There
are many, many more operators... Use Ovid‘s Help menu to locate them.
Or see:
http://content.library.utoronto.ca/gerstein/subjectguides/ovidmedline_shortcuts.pdf

18. How does patient adherence to medication
regimens influence outcomes following surgery
for myocardial infarction?
Source:
Practical Screens:

19. Running your search

20. Running your search(es)
• Start with your first concept
– Search for the subject headings first
– Then search keywords
– 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

21. 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

22. Applying practical & methodological
screening criteria

23. Screening
• Two kinds: practical and methodological
• Why?
– Use practical screening to identify a broad range
of potentially useful studies
– Use methodological screening to identify the best
available studies

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

25. 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?*
*Fink, A. (2005). Conducting Research Literature Reviews. London: Sage.

26. Applying Screens (or limits)
• Apply practical screens by using “limits” (may
also be called “search options”)
• Apply methodological screens by reading
through the articles

27. Next steps

28. 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 a new
concept map

29. Working with your results
• Export search results from each database or
website into a citation manager (i.e.,
RefWorks)
• Remove duplicates
• Remove inappropriate studies by applying
methodological screens

30. Synthesizing the results

31. Look for Patterns
• What conclusions did these studies reach?
• Which studies agreed/disagreed with the
consensus?
• Consider using a synthesis matrix:
www.ncsu.edu/tutorial_center/writespeak/download/Synthesis.pdf

32. 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*
*Fink, A. (2005). Conducting Research Literature Reviews. London: Sage.

33. Recap
1. What is a quality search?
2. Develop a research question that’s ________
3. Which boolean operator do you use to
combine synonymous search terms?
4. What screens should you apply to your
results?

34. Questions
Robin Featherstone
Clinical Medicine Librarian
UWO
rfeathe@uwo.ca
Selinda Berg
Clinical Medicine Librarian
Windsor
sberg@uwindsor.ca