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Evidence-Based Medicine
(EBM)
Arnuparp Lekhakula
Department of Internal Medicine
Faculty of Medicine
Prince of Songkla University
Scope of Presentation
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Why EBM?
What is EBM?
How to use and practise EMB
Application of EBM
Limitations of EBM
Why EBM?
Negative correlation between knowledge of
hypertension and the years since graduation
from the medical school
Why EBM?
• Paradigm shift
• Evidences create frequent, major changes
in the way of patient care
• Both our up-to-date knowledge and our
clinical performance deteriorate with time
• Quality of health care
• Second opinion
• Patient education
• Cost of health care
• Third party
Why EBM?
• Eyepatches for corneal abrasion
No benefit
• Anti-arrhythmic agent :
Encainide and flecainide - suppress
ventricular arrhythmia
Higher mortality rate than control
?Outcome
• Steroids in prematurity
Beneficial effect
What is
Evidence-Based Medicine?
Evidence-Based Medicine
The practice of EBM is the integration of
 individual clinical expertise
with the
 best available external clinical evidence
from systematic research
and
 patient’s values and expectations
Assumption of the Old Paradigm
• Clinical experiences are a valid way for
clinical practice
• Pathophysiologic principles are adequate
guides for clinical practice
• Assessment of evidence is adequate
through thorough traditional medical
training plus the use of common sense
• Experts are authority who should be
consulted in solving clinical problems
Solving Problems
under Old Paradigm
• Reflect on own clinical experiences
• Reflect on underlying pathophysiology
• Consult an updated textbook
• Ask content experts
• Read introduction and discussions of
journals
Assumption of the New Paradigm
• Clinical experiences are of limited values
in decisions about clinical practices
• Pathophysiologic principles can lead to
inaccurate judgement about clinical
practices because of incomplete
understandings of all related principles
Assumption of the New Paradigm
• Assessment of evidence requires
knowledge of rules of evidences in
addition to training and common sense
• Experts should be challenged to produce
evidence on which their recommendations
are based
Solving Problems with EBM
• Define a patient problem
• Convert the problem into answerable
questions
• Search literature for the best evidence
• Critically appraise that evidence for its
validity (closed to the truth) and
usefulness (clinical applicability)
• Apply the results back to the patient
• Evaluate our performance
Evidence-Based Medicine
Clinical problem
Building a good question
Applying the evidence
to the patient
Critically appraising
the evidence
Carrying out an
efficient, thoughtful
search of evidence
Choosing the best
evidence from the
search output
How to use and
practise EBM?
Clinical Questions Arise from :
• Clinical findings
• Etiology
• Differential diagnosis
• Diagnostic test
• Prognosis
• Clinical prediction
• Therapy
• Prevention
• Economics
Building a Good Question
‘PICO’
P atient
I ntervention
C omparison
O utcome
Weighing the Evidence
• Validity (Is it good and true?)
• Importance (Is it worth attention?)
• Relevance
(Is it worth putting in practice?)
Two Key Components of EMB
• Hierarchy of evidences
Clinical research
Physiological studies involving
animals & non-clinical outcomes
Clinical experiences
• Decision making
Application of evidences
Determinants of actions
Nature of Evidences
• Clinical Experiences
Unsystematic observations
Varying degree of bias
• Physiologic Evidences
Highly systematic & strict scientific rules
Limited generalization and inference
Different from clinical outcomes
• Clinical Research
Systematic clinical observation
Strategies to deal with bias
Systematic
Review
Meta-Analysis
RCT
Cohort
Case-Control
Cross-sectional
Case Reports
Hierarchy of Evidence
Three EBM Strategies for
Keeping Up-to-date
• Learning how to practise EBM
• Seeking and applying evidence-based
summaries generated by others
• Accepting evidence-based practice
protocols developed by colleagues
3 Different Modes of Practice
“Searching & appraising”
 provides
E-B care, but is expensive in time
and resources
“Searching only”
 much,
quicker, and if carried out among E-B
resources, can provide E-B care
“Replicating” the practice of experts
 quickest,
but may not distinguish evidencebased from ego-based recommendations
Patients can benefit
 Even if <10% of clinicians are capable of
practicing in the “searching & appraising”
mode (5% of GPs)
 As long as most of them practice in a
“searching” mode within high-quality
evidence sources (70-80% of GPs):
 Cochrane
Library, E-B Journals, E-B
Guidelines, etc
Cochrane Systematic Reviews (522; another 500 in preparation)
Database of Abstracts of Reviews of Effectiveness (1895)
Registry of Randomised Controlled Trials (218,355)
EBM in Medical Training
• Encourage learning
• Challenging
• Decreased the knowledge gap between
trainee and their teachers
• Increased the trainees’ confidence and
fostering life-long self-directed learning
Limitation of
Evidence-Based Medicine
The Limits of Evidence
• RCT gives average probability and not
the possible ranges of outcomes
• Patient’s choices informed by facts but
influenced by personality and preference
• Bias in research in posing questions and
getting answers
• Bias in publication
The Limits of EBM
• Incomplete and contradictory evidence
• Population effectiveness versus
individual effectiveness
• Difficulty of searching evidence in
emergency
• Force feeding by EBM may antagonize
many
Misapprehensions about EBM
• EBM ignores clinical experience and
clinical intuition
• Understanding of basic investigation
and pathophysiology plays no part in
EBM
• EBM ignores standard aspects of
clinical training, such as history taking
and physical examination
Evidence-Based Medicine
• is not “everybody already is doing it”
• is not subject matter in the textbook
• will not produce new findings
• will not produce better evidence
• is not “cook-book” medicine
• is not restricted to randomized trials and
meta-analysis
Filter of EBM
Clinical knowledge,
experience and guts
Patient’s
preference
Best Evidence
Clinical decision
“Absence of evidence”
is not
“Evidence of absence”