Evidence Based Medicine Lecture
Sandra A. Martin, M.L.I.S.
Health Sciences Resource Coordinator
Instructor of Library Services
John Vaughan Library Room 305B
marti004@nsuok.edu – 918-444-3263
Existing knowledge can prevent…
•Waste
•Errors
•Poor quality clinical care
•Poor patient experience
•Adoption of interventions of low value
•Failure to adopt interventions of high value
Source: Sir Muir Gray, Chief Knowledge Officer of Britain’s National Health
Service. Quoted on http://www.nks.nhs.uk/.
Harmful practices once supported by expert opinion
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Time period
Accepted practice
Shown to
be harmful
Impact on clinical
practice
From 500 bc
Blood Letting
1820
Ceased in 1910
1957
Thalidomide for
morning sickness in
early pregnancy
1960
Withdrawn when first
case report of severe
malformations
appeared
From 1900
Bed rest for acute
low back pain
1986
Still advised by some
doctors
1960s
Benzodiazepines
for mild anxiety
1975
“Diazepam”
prescribing fell in
1990s due to severe
dependence and
withdrawal symptoms
Late 1990s
Cox-2 inhibitors to
treat arthritis
2004
Withdrawn following
legal cases in the US
Source: Adapted from How to read a paper: the basics of evidence-based medicine. 4th edition. By
Trisha Greenhalgh. 2010 Blackwell Publishing
Information Retrieval for Evidence
Based Patient Care
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Using research findings versus conducting research
Retrieving and evaluating information that has direct
application to specific patient care problems
Selecting resources that are current, valid and available
at point-of-care
Developing search strategies that are feasible within
time constraints of clinical practice
Learning Objectives
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At the end of the presentation, you will be able to:
• Define evidence-based medicine (EBM)
• Understand the Five Steps to practice EBM
• Use the 6S hierarchy to conduct an efficient search for
the best evidence
• Access online pre-appraised resources
• Locate print and online tools to assist in critical
appraisal of individual studies
• Practice the Five Steps in clinical settings
What is EBM?
www.cebm.net
“Evidence-based medicine is the integration of best
research evidence with clinical expertise and patient
values”
Patient
Concerns
EBMClinical
Best research
evidence Expertise
Sackett DL, Rosenberg WMC, Gray JAM, Haynes RB, Richardson WS: Evidence based medicine: what it is and what it
isn’t. BMJ 1996;312:71-2.
Evolution of EBM in the Literature
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Term first appeared in the literature in a 1991 editorial in
ACP Journal Club Volume 114, Mar-April 1991, pp A-16
Seminal article by the Evidence-Based Medicine
Working Group published in JAMA Volume 268, No. 17,
1992, pp 2420-2425
Fundamentally new approach
becomes widely recognized
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JAMA published a series of Users’ Guides to the Medical
Literature that served as the first learning tools
Courses were developed in residency training and
medical school curricula
The first handbook, Evidence-Based Medicine: How to
practice and teach EBM, by Sackett, et al, was published
in 1996. Fourth edition published in 2010.
New York Times listed EBM as one of its ideas of the
year in 2001
BMJ listed EBM as one of the 15 greatest medical
milestones since 1840
Integration of EBM into medical school
curricula patient-doctor courses
EBM Process – 5 Steps
1.
2.
3.
4.
5.
ASK: Convert need for information into answerable
question
ACQUIRE: Find best evidence to answer the question
APPRAISE: Critically appraise evidence for validity,
impact, and applicability
APPLY: Integrate evidence with clinical expertise and
patient values
ASSESS: Evaluate own effectiveness
New Approach Requires New Skills
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Clinical question formulation
Search and retrieval of best evidence
Critical appraisal of study methods to determine validity
of results
Background v Foreground Knowledge
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Both types of knowledge needed
Varies over time
Depends on experience with condition
Point A: Student – limited experience
Point B: Resident – growing clinical experience
Point C: Attending – extensive experience
Note: Diagonal line shows “we’re never too green to
learn foreground knowledge, nor too experienced to
outlive the need for background knowledge”
Source: Evidence-based medicine: how to practice and teach it. 4th edition. By Straus, et. al.
Churchill Livingstone Elsevier
Answerable Questions
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Arise in patient care setting and are:
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Important to the patient’s well being
Fill gaps in your clinical knowledge
Feasible to answer in time available
Clinical Questions
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Four Common Types
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Therapy/prevention
Diagnosis
Etiology
Prognosis
Therapy Question Example
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In patients with primary open angle
glaucoma or ocular hypertension
[Patient/Population], do topical
medications to reduce intraocular
pressure [Intervention] versus no
treatment [Comparison Intervention],
delay visual field defect progression
[Outcome]?
PICO Model
PICO-
Patient or population
Intervention
Comparison Intervention
Outcome
Possible Search Terms

Primary open angle glaucoma, POAG,
Ocular hypertension, OHT, topical
medications, intraocular pressure, IOP,
visual fields, VF
Evidence Based Retrieval
1. Find the answer that is supported by valid
studies appropriate to the type of
question and that is available in a timely
manner.
2. Requires search terms plus best study design
for question plus highest level of evidence
Best Study Design for Type of Question
Type of Question
Study Design
Therapy/prevention
Randomized controlled
trials
Diagnosis
Prospective cohort, blind
comparison to a gold
standard
Prognosis
Cohort, Case Control, Case
Series
Etiology/Harm
Cohort, Case Control, Case
Series
Is All Evidence Created Equal?
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Small portion of medical literature is immediately useful
to answer clinical questions
Understanding “wedge or pyramid of evidence” is
helpful in finding highest level of evidence
High levels of evidence may not exist for all questions
due to nature of medical problems and research
limitations
As you move up the pyramid the amount of available literature decreases, but it increases in its relevance to the
clinical setting.
Source: Sackett, D.L., Richardson, W.S., Rosenberg, W.M.C., & Haynes, R.B. (1996). Evidence-Based Medicine: How to practice and teach EBM. London:
Churchill-Livingstone.
Levels of Evidence
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Grade the quality of evidence based on the
design of the clinical study
Variety of hierarchies in use
American Academy of Family Physicians SORT
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Level A
 Systematic reviews of randomized controlled trials including metaanalyses
 Good-quality randomized controlled trials
Level B
 Good-quality nonrandomized clinical trials
 Systematic reviews not in Level A
 Lower-quality randomized controlled trials not in Level A
 Other types of study: case control studies, clinical cohort studies,
cross sectional studies, retrospective studies, and uncontrolled
studies
Level C
 Evidence-based consensus statements and expert guidelines
DynaMed and FirstConsult
Hierarchy of Published Evidence for
Intervention Studies
Level of Evidence
Description
Study Example
1
Randomized clinical trial with
low study errors or a metaanalysis
Optic neuritis treatment trial N
Engl J Med. 1992; 326:581-588
2
Randomized clinical trial with
high study errors
Scatter laser photocoagulation
for occult choroidal
neovascularization Arch
Ophthalmol. 1996; 114:14561464
3
Clinical trial with a control group,
with nonrandom treatment
allocation
Thrombolytic therapy for acute
retinal arterial occlusion Am J
Ophthalmol. 1992; 113:429-434
4
Intervention case series
Macular translocation surgery
for the treatment of CNVM and
AMD Am J Ophthalmol. 1968;
66:597-603
5
Interventional case report
Removal of a choroidal
neovascular membrane Retina.
1994; 14:125-129
Key developments that streamlined the
practice of EBM
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Advances in ease of accessing and understanding
information
Development of preprocessed (preappraised) tools
Improvements in search interfaces to MEDLINE
Collaboration between EBM Working Group and
National Library of Medicine in development of hedges,
“clinical queries” tool, that filters search results to
specific study types and levels of evidence
Dissemination of systematic reviews of primary studies
and growth of the Cochrane Collaboration
4S Hierarchy
Highest Level of Evidence - Critically Appraised Content
Evidence Based Summaries
Dynamed, Clinical Key, First
Consult, UptoDate
ACP Journal Club, DARE
Cochrane Database of
Systematic Reviews
Clinical Key & Ovid MEDLINE
limited to Study Types and
Clinical Queries
SOURCE: Haynes, R. B. (2001). Of studies, syntheses, synopses, and systems: the “4S” evolution of services for
finding current best evidence. Evidence-Based Medicine, 6 (2), 36-38. Retrieved 2-07-07 from
http://ebm.bmj.com/cgi/reprint/6/2/36
6S Hierarchy
• Summaries:
•
•
•
Clinical Key
First
Consult
Dynamed
New Resource – Clinical Key
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Full text access to 1,000 books and 500 journals in every
medical and surgical specialty
Ophthalmology – Over 60 full text books
Includes 12 Content Types
Access to information at all levels from topic overview to
evidence-based data in one search
Smart search engine matches first few letters of search
word/words to relevant clinical content
No complicated search strategies or Boolean connectors
Easier than Google – but with reliable, evidence-based
results
Clinical Key includes 3 Levels Plus
Books and Overviews
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Summaries,
Synthesis,
Studies
Summaries
• FirstConsult
– Available through NSU subscription to Clinical
Key for iPhone or iPad only
– Create a personal account in Clinical Key
– Download the app from the Apple app store
– Login with your Clinical Key username and
password
– Summaries are detailed and include sections
on Differential Diagnosis
– Eyes and Vision topics well covered
Summaries
• DynaMed
– Summaries for more than 3,000 topics
– Monitors >500 medical journals and
systematic review databases
– Updated daily
– Each article evaluated for clinical relevance
and scientific validity
– Includes “graded evidence”
Glaucoma Summary
Evidence-based answer found in 1 minute, 39 seconds
Summaries
• UptoDate
– Evidence based summaries of over 9,500
topics in over 20 specialties, over 250,000
references, and drug database
– Ophthalmology not one of the specialties
– Good for information on systemic conditions
– Updated continuously
Clinical Question
“In hypertensive patients older than 75 with
atrial fibrillation (P), does the use of
warfarin (I), compared to aspirin (C), result
in fewer strokes (O)?”
1:54
Syntheses
• Cochrane Database of Systematic
Reviews (DSR)
– Part of the Cochrane Library (1996)
– 916 completed reviews, 1905 protocols
– Among the highest level of evidence upon
which to base treatment decisions
– Includes Dx since 2008
– Eyes & Vision Research Group
• Contains over 165 reviews
Systematic Review
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Analyzes data from several primary studies to
answer a specific clinical question
Provides search strategies and resources used
to locate studies
Includes specific inclusion and exclusion criteria
(results in less bias)
Meta-Analysis (subclass) statistically
summarizes results of several individual studies
Access full text of Cochrane reviews in OVID
Cochrane DSR
Review found in 15 seconds
Copyright: The Cochrane Library, Copyright 2009, The Cochrane Collaboration
Appraisal Required by User
Primary (Original) Studies
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Articles that report results of original
research investigations
Conclusions supported by data and
reproducible methodology
Require time to acquire and appraise
Good Sources: Ovid MEDLINE and
Clinical Key
When to search for original studies
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If the other “S’s” don’t provide the answer,
search for original studies
“Do it yourself” appraisal territory
You must appraise quality of the study or
find analysis in evidence based summary
Limit to “Study Type” in Clinical Key or
“Clinical Queries” in Ovid MEDLINE
Databases
• MEDLINE
– Premiere biomedical database from the NLM
(National Library of Medicine)
– Covers 1946-present
– Indexes >4000 international biomedical
journals
– Full text available for many articles
– Access through Ovid
MEDLINE Indexing
Search Query
Boolean Connectors
MEDLINE Search Limits
• Limit search results to study type
– Randomized controlled trials
– Clinical trials
• In OVID, limit by “Clinical Queries”
• Appraise study for validity and relevance
Ovid MEDLINE Clinical Queries
Levels of Evidence in Ovid based on AAFP SORT
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Level A = “Specificity” in Ovid Clinical Queries
 Systematic reviews of randomized controlled trials including metaanalyses
 Good-quality randomized controlled trials
Level B = “Sensitivity” in Ovid Clinical Queries
 Good-quality nonrandomized clinical trials
 Systematic reviews not in Level A
 Lower-quality randomized controlled trials not in Level A
 Other types of study: case control studies, clinical cohort studies,
cross sectional studies, retrospective studies, and uncontrolled
studies
Level C
 Evidence-based consensus statements and expert guidelines
Take Home Points
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Focused clinical question (PICO) reveals your
search terms
Start your search at top of 6S hierarchy and
work down
Be aware of the filter, i.e., levels of evidence,
speed of updating
Look at more than one resource in the
hierarchy. Findings may differ
Apply in clinical settings; Assess your progress
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