Evidence Based Medicine

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Transcript Evidence Based Medicine

Existing knowledge can prevent…
•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/.
Learning Objectives
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 4S approach to organizing clinical research
• Conduct an efficient online search to track down best
• Access online and print tools to critically appraise the
• Use the Five Steps for research and clinical care
What is EBM?
“Evidence-based medicine is the integration of best
research evidence with clinical expertise and patient
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
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
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
New Approach Required New Skills
Clinical question formulation
Search and retrieval of best evidence
Critical appraisal of study methods to ascertain validity of
Integration of EBM into medical school
curricula patient-doctor courses
Key developments that streamlined the
practice of EBM
Advances in ease of accessing and understanding
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
EBM Process – 5 Steps
ASSESS: Recognize and prioritize important patient
ASK: Construct clinical questions that facilitate an
efficient search
ACQUIRE: Track down the best evidence to answer the
APPRAISE: Systematically evaluate best available
evidence for validity, importance, and usefulness
APPLY: Interpret the applicability of evidence to
specific problems, given patient preferences and values
4S Hierarchy
6S Hierarchy
Point of Care Summaries:
Uptodate, Dynamed,
DARE (synopses of syntheses)
ACP Journal Club (synopses of
Cochrane and other Systematic
Clinical Key Searches Limited to
Study Types, MEDLINE Searches
limited to 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
Critically Appraised Content
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
2. Requires search terms plus best study design
for question plus highest level of evidence
Extract search terms from question
Therapy/Prevention Question in PICO
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]?
Possible Search Terms
Ocular hypertension, OHT, intraocular
pressure, IOP, primary open angle
glaucoma, POAG, medical treatment,
medical intervention, visual fields, VF
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.
Best Study Design for Type of Question
Type of Question
Study Design
Randomized controlled
Prospective cohort, blind
comparison to a gold
Cohort, Case Control, Case
Cohort, Case Control, Case
• 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
• UptoDate
– Evidence based summaries of over 9,500
topics in over 20 specialties
– Ophthalmology not one of the specialties
– Good for information on systemic conditions
– Available through individual subscription.
Online access plus Mobile app for iPhone and
iPad. Cost: $199 per year in training; $499
per year in practice
• 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
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
Levels of Evidence
Grade the quality of evidence based on the
design of the clinical study
Variety of hierarchies in use
Levels of Evidence in Ovid based on AAFP SORT
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
Level C
 Evidence-based consensus statements and expert guidelines
Appraisal Required by User
Primary (Original) Studies
Articles that report results of original
research investigations
Conclusions supported by data and
reproducible methodology
Require time to acquire and appraise
Good Sources: MEDLINE and Clinical
When to search for original studies
If the other “S’s” don’t provide the answer,
search for original studies
Appraise best available evidence or find
analysis in evidence based resource
Use “clinical queries” limit in Ovid
Limit to “Study Type” in Clinical Key
Least efficient (in terms of time)
Take Home Points
Focused clinical question (PICO) reveals
your search terms
Start your search at top of 4S 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
Practice makes perfect
Evidence Based Medicine Lecture
Sandra A. Martin, M.L.I.S.
Health Sciences Resource Coordinator
Instructor of Library Services
John Vaughan Library Room 305B
[email protected] – 918-444-3263