Introduction to Evidence-Based Medicine (EBM)

1
Presented by
Marc Imhotep Cray, M.D.
Companion Article:
Masic I, Miokovic M, Muhamedagic B. Evidence
Based Medicine-New Approaches and Challenges.
Acta Informatica Medica. 2008;16(4):219-225.

Learning Objectives
2
By the end of this presentation the learner should:
 Understand the background, history, definition and
importance of evidence-based medicine.
 Know how to formulate clinically relevant,
answerable questions using the Patient
Intervention Comparison Outcome (PICO)
framework.
 Be able to systematically perform a literature
search to identify relevant evidence.
 Understand the importance of assessing the
quality and validity of evidence by critically
appraising the literature.
 Know that different study designs provide varying
types and levels of evidence.

Scope of Evidence-Based Medicine
3
 Term "evidence-based medicine" has
two main tributaries
 First is insistence on explicit evaluation of
evidence of effectiveness when issuing
clinical practice guidelines and other
population-level policies
 Second is introduction of epidemiological
methods into medical education and
individual patient-level decision-making
o This tributary had its foundations in clinical
epidemiology a discipline that teaches medical
students and physicians how to apply clinical and
epidemiological research studies to their practices

Graphic from: Guyatt G et al. (Eds). Users’ Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice 3rd Ed. New York: McGraw-Hill Education-JAMA Network, 2015.
Background, history and definition
EBM methods were published to a broad
physician audience in a series of 25 "Users’
Guides to the Medical Literature" published in
JAMA between 1993 and 2000 by the
Evidence-based Medicine Working Group at
McMaster University.

5
EBM
Clinical
Judgement
Relevant
Scientific
Evidence
Patients’ Values
and Preferences
What is Evidence-Based Medicine?
Redrawn after: Sackett DL, et al. BMJ. 1996; (7023): 71-72.
 Evidence-based medicine (practice) is a systematic process
primarily aimed at improving care of patients EBM Triad
includes:

What is EBM? (2)
6
Sackett and colleagues describe evidence-based
medicine (a.k.a. evidence-based practice[EBP])
as “the conscientious, explicit and judicious use
of current best evidence in making decisions
about the care of individual patients”
Sackett DL, et al. BMJ. 1996; (7023): 71-72.

What is EBM? (3)
7
“Evidence-based medicine (EBM) is the process
of systematically reviewing, appraising and using
clinical research findings to aid the delivery of
optimum clinical care to patients”
Rosenberg W, Donald A. Evidence based medicine: an approach to clinical
problem-solving. BMJ 1995; 310: 1122–1126.

What is EBM ? (4) Capsule
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EBM is an approach to medical practice
intended to optimize decision-making by
emphasizing use of evidence from well-
designed and well-conducted research
 Although all medicine based on science has some
degree of empirical support EBM goes further
classifying evidence by its scientific strength and
requiring that only strongest types evidence (i.e.,
meta-analyses, systematic reviews, randomized
controlled trials) can yield strong recommendations
o weaker types of evidence (such as from case-control
studies) can yield only weak recommendations

History of EBM
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 1940s-Formal assessment of medical interventions
using controlled trials well established
 1972-Prof. Archie Cochrane, director of Medical
Research Council Epidemiology Research Unit in
Cardiff expressed what later came to be known as
evidence-based medicine (EBM) in his book
Effectiveness and Efficiency: Random Reflections on
Health Services
 Late 1980s and early 1990s-EBM concepts were
developed into a practical methodology by groups at
Duke University in North Carolina (David Eddy) and
McMaster University in Toronto (Gordon Guyatt and
David Sackett)

History of EBM (2)
10
 1992- UK government funded establishment of
Cochrane Centre in Oxford  objective was to facilitate
preparation of systematic reviews of randomized
controlled trials of healthcare
 1993-Cochrane Centre expanded into an international
collaboration of centres, of which (as of 2009) there
were thirteen, whose role is to co-ordinate activities of
11,500 researchers
NB: Cochrane Collaboration considered as one of critical
factors in spreading concept of EBM worldwide

Main elements of EBM
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 EBM is part of multifaceted process of assuring
clinical effectiveness main elements are:
 Production of evidence through research and
scientific review
 Production and dissemination of evidence-based
clinical guidelines
 Implementation of evidence-based, cost effective
practice through education and management of
change
 Evaluation of compliance with agreed practice
guidance through clinical audit and outcomes-
focused incentives

Key principles of EBM
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EBM involves a number of key principles
discussed in turn during course of presentation:
 Formulate a clinically relevant question
 Identify relevant evidence
 Systematically review and appraise evidence
identified
 Extract most useful results and determine whether
they are important in your clinical practice
 Synthesize evidence to draw conclusions
 Use clinical research findings to generate guideline
recommendations which enable clinicians to deliver
optimal clinical care to patients
 Evaluate implementation of EBM

Core of Evidence-Based Medicine
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 At core of EBM is a care and respect for patients who
will suffer if clinicians fall prey to muddled clinical
reasoning and to neglect or misunderstanding of
research findings
 Practitioners of EBM strive for a clear & comprehensive
understanding of evidence underlying their clinical
care and  work w each pt. to ensure that chosen
courses of action are in that pt’s best interest
 Practicing EBM requires clinicians to understand how
uncertainty about clinical research evidence intersects
w an individual pt’s predicament, values & preferences

Logic behind EBM
14
 To make EBM more acceptable to clinicians
and to encourage its use best to turn a
specified problem into answerable questions
by examining:
 Person or population in question
 Intervention given
 Comparison (if appropriate)
 Outcomes considered
 Next, it is necessary to refine problem into
explicit questions then check to see
whether evidence exists
 But where can we find information to help us
make better decisions?

What is involved in identification, appraisal and
application of evidence summarized in reviews?
15
Framing questions
↓
Identifying relevant reviews
↓
Assessing quality of review and
its evidence
↓
Summarizing the evidence
↓
Interpreting finding

16
https://www.healthcatalyst.com/5-reasons-practice-evidence-based-medicine-is-hot-topic

Where can we find information?
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 Common sources include:
 Personal experience for example, a bad drug
reaction
 Reasoning and intuition
 Colleagues
 Published evidence
o meta-analyses, systematic reviews and
randomized controlled trials
NB: By becoming educated in strength of published
evidence (and critical appraisal ), in contrast to more
traditional--less rigorous--sources of information use of
ineffective, costly or potentially hazardous interventions
can be reduced

Formulating Clinical Questions
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 In order to practice evidence-based
medicine initial step = converting a clinical
encounter into a clinical question
 A useful approach to formatting a clinical (or
research) question  Patient Intervention
Comparison Outcome (PICO) framework

Formulating Clinical Questions (2)
Patient Intervention Comparison Outcome (PICO)
framework
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Question is divided into four key components:
1. Patient/Population: Which pts. or popul. group of
pts. are you interested in?
 Is it necessary to consider any subgroups?
2. Intervention: Which intervention/treatment is being
evaluated?
3. Comparison/Control: What is/are main alternative/s
compared to intervention?
4. Outcome: What is most important outcome for
patient?
 Outcomes can include short- or long-term measures,
intervention complications, social functioning or quality of
life, morbidity, mortality or costs

PICO Framework illustrated
20
Patient Children with congestive heart failure
Intervention Carvedilol (a β-blockers )
Comparison No carvedilol
Outcome Improvement of CHF symptoms
Clinical Encounter
Ali, 30 years old, was diagnosed with heart failure at 4
years old and prescribed a beta-blocker which
dramatically improved his symptoms. Ali’s 5- year-old
daughter, Leda, has been recently diagnosed with
chronic symptomatic CHF. Ali asks you, whether his
daughter should also be prescribed a beta-blocker.
Question: Is there a role for beta-blockers in the
management of heart failure in children?

Types of research questions (=Tx/ Etio/ Dx/ Px)
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Not all research questions ask whether an intervention
is better than existing interventions or no Tx at all
 From a clinical perspective EBM is relevant for three
other key domains:
1. Etiology: Is exposure a risk factor for developing a certain
condition?
2. Diagnosis: How good is diagnostic test (history taking,
physical examination, laboratory or pathological tests and
imaging) in determining if a pt. has a particular condition?
 Questions usually asked about clinical value or diagnostic
accuracy of test
3. Prognosis: Are there factors related to pt. that predict a
particular outcome (disease progression, survival time after
Dx of disease, etc.)?
 Px is based on characteristics of pt. (“prognostic factors”)

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Important that pt. experience is taken into
account when formulating clinical question
 (p)atient experience may vary depending on which
pt. population is being addressed
 Following pt. views should be determined:
o Acceptability of proposed (i)ntervention being evaluated
o Preferences for Tx options already available (c)
o What constitutes an appropriate, desired or acceptable
(o)utcome
 NB: Incorporating above pt. views will ensure clinical
question is patient-centered and therefore clinically
relevant

Identifying Relevant Evidence
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 Three Ways to Use the Medical Literature
 Staying Alert to Important New Evidence
 Problem Solving
 Asking Background & Foreground Questions
 Analyzing information
 In using evidence it is necessary to:
o Search for and locate it
o Appraise it
o Interpret it in context
o Implement it
o Store and retrieve it
o Ensure it is updated
o Communicate it

Ways to Use Medical Literature
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Medical student, in early training, seeing a
patient with newly diagnosed type 2 diabetes
mellitus She will ask questions such as:
 What is type 2 diabetes mellitus?
 Why does this patient have polyuria?
 Why does this pt. have numbness & pain in his legs?
 What treatment options are available?
 These questions address normal physiology and
pathophysiology assoc. w a medical condition
 Traditional medical textbooks that describe
underlying pathophysiology or epidemiology of a
disorder provide an excellent resource for addressing
these background questions

Ways to Use Medical Literature (2)
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 …In contrast, sorts of foreground questions
that experienced clinicians usually ask
require different resources, namely using
current medical literature for pt.-related
problem solving
 Formulating a question is first step and
critical skill for this evidence-based
practice (EBP)
 Ways to use medical literature that follow
provide an opportunity to start learning &
practicing the skill

26
“Clinicians do Problem Solving”
 Experienced clinicians managing a pt. w T2DM
will ask questions such as:
 In pts w new onset T2DM, which clinical features or
test results predict development of diabetic
complications?
 In pts with T2DM requiring drug therapy, does
starting w metformin Tx yield improved diabetes
control and reduce long-term complications better
than other initial treatments?
NB: Here, clinicians are defining specific questions
raised in caring for pts then consulting the
medical literature to resolve these questions

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Most valuable single free access point is The
Cochrane Library
 The Cochrane Library contains high-quality,
independent evidence to inform all healthcare
decision-making
 An alternative to alerting systems are
secondary evidence based journals
 For example, in internal and general medicine, ACP
Journal Club (http://acpjc.acponline.org) publishes
synopses of articles that meet criteria of both high
clinical relevance and methodologic quality
See: Haynes RB, Cotoi C, Holland J, et al; McMaster Premium Literature
Service (PLUS) Project. Second-order peer review of the medical literature
for clinical practitioners. JAMA. 2006;295(15):1801-1808

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Most efficient strategy for ensuring you are
aware of recent developments relevant to your
practice is to subscribe to e-mail alerting
systems, such as EvidenceAlerts
 A free service w research staff screening approx.
45, 000 articles per year in more than 125 clinical
journals for methodologic quality and a worldwide
panel of practicing physicians rating them for
clinical relevance and newsworthiness

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Asking Background & Foreground Questions
One can think of first set of
questions, those of medical
student, as background
questions and of browsing and
problem-solving sets as
foreground questions
 In most situations you
need to understand
background thoroughly
before it makes sense to
address foreground issues
Guyatt G et al. (Eds). Users’ Guides to the Medical Literature:
Essentials of Evidence-Based Clinical Practice 3rd Ed. New York:
McGraw-Hill Education-JAMA Network, 2015.

Marc Imhotep Cray, M.D. 30
 Five Types of Foreground Clinical Questions
 In addition to clarifying population,
intervention or exposure, and outcome, it
is productive to label nature of question
that you are asking
 Finding a Suitably Designed Study for Your
Question Type
 You need to correctly identify category of
study b/c to answer your question, you
must find an appropriately designed
study
o For example, if you look for a randomized
trial to inform properties of a diagnostic test,
you will not find answer you seek

There are 5 fundamental types of
clinical questions
31
1. Therapy: determining effect of interventions on patient
important outcomes (symptoms, function, morbidity,
mortality, and costs)
2. Harm: ascertaining effects of potentially harmful agents
(including therapies from first type of question) on
patient-important outcomes
3. Differential diagnosis: in patients with a particular
clinical presentation, establishing the frequency of the
underlying disorders
4. Diagnosis: establishing power of a test to differentiate
Betw. those with and without a target condition or disease
5. Prognosis: estimating a patient’s future course
 We will now review study designs associated with 5
major types of questions.

Structure of Randomized Trials
 To answer questions about a therapeutic issue, we seek a
randomized trial (group assignment analogous to flipping a coin)
 Once investigators allocate participants to treatment or control
groups they follow them forward in time to determine whether
they have, for instance, a stroke or myocardial infarction what
we call outcome of interest
Guyatt G et al. (Eds). Users’ Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice
3rd Ed. New York: McGraw-Hill Education-JAMA Network, 2015.

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Structure of Observational Cohort Studies
 Ideally, we would also look to randomized trials to address issues of harm
 For most potentially harmful exposures, however, randomly allocating patients is
neither practical nor ethical
o For example , one cannot suggest to potential study participants that an
investigator will decide by the flip of a coin whether or not they smoke during
next 20 years
 For exposures such as smoking, best one can do is identify observational
studies (subclassified as cohort or case-control studies)  provide less
trustworthy evidence than randomized trials

Structure of Studies of Differential
Diagnosis
34
 For sorting out differential diagnosis investigators collect a
group of patients with a similar presentation (eg, painless jaundice,
syncope, or headache), conduct an extensive battery of tests,
and if necessary follow patients forward in time
 Ultimately, for each pt. investigators hope to establish underlying
cause of symptoms and signs with which pt. presented

Structure of Studies of Diagnostic
Test Properties
35
 In diagnostic test studies, investigators identify a group of patients
among whom they suspect a disease or condition of interest exists
(such as tuberculosis, lung cancer, or iron deficiency anemia)
which we call the target condition
 Pts. undergo new diagnostic test and a reference standard (also
referred to as gold standard or criterion standard)
 Investigators evaluate diagnostic test by comparing its classification
of pts. w that of reference standard

36
Structure of Studies of Prognosis
 Final type of study examines a patient’s prognosis and may identify factors
that modify that prognosis
 Here, investigators identify pts who belong to a particular group (such as
pregnant women, pts. undergoing surgery, or pts w cancer) with or without
factors that may modify their prognosis (such as age or comorbidity)
 The exposure here is time investigators follow up pts to determine if they
experience the target outcome such as an adverse obstetric or neonatal event
at end of a pregnancy, a myocardial infarction after surgery, or survival in cancer

37
https://www.healthcatalyst.com/5-reasons-practice-evidence-based-medicine-is-hot-topic

Finding Current Best Evidence
38
 Searching for Evidence is a Clinical Skill
 Searching for current best evidence in
medical literature has become a central skill
in clinical practice
 On average, clinicians have 5 to 8 questions
about individual patients per daily shift and
regularly use online evidence-based medicine
(EBM) resources to answer them
See: Chapter 4, Finding Current Best Evidence. In: Guyatt G et al.
(Eds). Users’ Guides to the Medical Literature: Essentials of
Evidence-Based Clinical Practice 3rd Ed. New York: McGraw-Hill-
JAMA Network, 2015.

Categories of EBM Resources
39
Summaries and guidelines
 UpToDate
 DynaMed
 Clinical Evidence
 Best Practice
 US National Guidelines
Clearinghouse
Preappraised research
 ACP Journal Club
 McMaster PLUS
 DARE
 Cochrane
 Evidence Updates
Nonpreappraised research
 PubMed (MEDLINE)
 CINAHL
 CENTRAL
 Filters:
 Clinical Queries in PubMed
Federated searches (engines)
 ACCESSSS
 Trip
 SumSearch
 Epistimonikos
Abbreviations: ACCESSSS, ACCess to Evidence-based Summaries, Synopses,
Systematic Reviews and Studies; CENTRAL, Cochrane Central Register of Controlled
Trials; CINAHL, Cumulative Index to Nursing and Allied Health Literature; DARE,
Database of Abstracts of Reviews of Effects.

http://www.cochranelibrary.com/
Free EBM alerting system

Databases included in The Cochrane Library
41
Belsey J. What is evidence-based medicine? Hayward Medical Communications, 2009.

https://plus.mcmaster.ca/EvidenceAlerts/
Free EBM alerting system

https://www.nlm.nih.gov/bsd/pmresources.html
Free Medical Literature Research Portal

http://www.medscape.com/
http://jama.jamanetwork.com/journal.aspx
Peer-Reviewed Publications, News, Alerts and CME

Critically Appraising the Evidence
45
Once all possible studies have been identified
w literature search each study needs to be
assessed for eligibility against objective criteria
for inclusion or exclusion
Having identified those studies that meet
inclusion criteria they are subsequently
assessed for methodological quality using a
critical appraisal framework
 Despite satisfying inclusion criteria, studies
appraised as being poor in quality should also be
excluded

Critical appraisal (2)
46
Critical appraisal is process of systematically
examining available evidence to judge its
validity, and relevance in a particular context
Appraiser should make an objective
assessment of study quality and potential for
bias
Note: Methodological checklists for critically appraising
study designs will be covered in a subsequent lecture

Critical appraisal (3)
47
Important to determine both internal validity
and external validity of study:
 External validity: extent to which study findings are
generalizable beyond limits of study to study’s
target population.
 Internal validity: Ensuring that study was run
carefully (research design, how variables were
measured, etc.) and extent to which observed
effect(s) were produced solely by intervention being
assessed (and not by another factor)
 Three main threats to internal validity (confounding,
bias and causality) for each of the key study designs are
discussed in subsequent lectures

Evaluating the Literature: Capsule
48
Theodore J Gaeta et al. Evaluating the Literature.
Accessed 07-08-17
Available at http://emedicine.medscape.com/article/773527
…reviewing medical literature poses a challenge to busy
physicians. A willingness and ability to do so enhance
quality of practice they bring to each of their patients.
To save time, a brief primary survey of article of interest
informs reader as to potential value of findings and to
whether a more in-depth review is indicated. If so, this
detailed analysis (secondary survey) allows reader to
determine whether article's conclusion is supported by its
results and whether these results are believable.
Knowledge of standard anatomy of an article and
idiosyncrasies of various types of studies will assist reader
to intelligently review medical literature efficiently…

Conclusion: Using the Medical Literature
Provides for Optimal Patient Care.
49
Guyatt G et al. (Eds). Users’ Guides to the Medical Literature: Essentials of Evidence-
Based Clinical Practice 3rd Ed. New York: McGraw-Hill Education-JAMA Network, 2015.

50See next slide for links to tools and resources for further study.

Sources and further study:
51
Textbooks
 Kaura A. Evidence-Based Medicine: Reading and Writing Medical
Papers (Crash Course Series). Philadelphia: Mosby- Elsevier,
2012.
 Guyatt G et al. (Eds). Users’ Guides to the Medical Literature:
Essentials of Evidence-Based Clinical Practice 3rd Ed. New York:
McGraw-Hill Education-JAMA Network, 2015.
 Swiger KJ et al. (Eds). 50 studies every internist should know.
New York: Oxford University Press, 2015.
Cloud Folders
 EBM (Evidence Based Medicine), Reading the Medical Literature
and Medical Writing

External Links
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Lefebvre, C., Manheimer, E., Glanville, J., 2011. Searching for studies. In:
Higgins, J.P.T., Green, S. (Eds.), Cochrane Handbook for Systematic Reviews of
Interventions. Version 5.1.0 (updated March 2011). The Cochrane
Collaboration. National Institute for Health and Clinical Excellence, March
2012. The Guidelines Manual. National Institute for Health and Clinical
Excellence, London. Available from: http:// www.nice.org.uk
Sackett, D.L., Rosenberg, W.M.C., 1995. The need for evidence based
medicine. J. R. Soc. Med. 88, 620–624.
Sackett, D.L., Rosenberg, W.M.C., Gray, J.A.M., Haynes, R.B., Richardson, W.S.,
1996. Evidence based medicine: What it is and what it isn’t. BMJ 312, 71–72.
Straus, S.E., McAlister, F.A., 2000. Evidence-based medicine: A commentary on
common criticisms. CMAJ 163, 837–841.

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