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EVIDENCE BASED
MEDICINE
for Beginners
Maria Fidelis Manalo, MD, Msc Epidemiology
Department of Community & Family Medicine
FEU-NRMF Medical Center
Philippines
Evidence-Based Medicine
Definition
“the conscientious,
explicit and judicious
use of current best
evidence in making
decisions about the care
of the individual patient”
David Sackett
EBM
Historical Evolution
 Has
roots going back to 19th c.
 Recently
broadened interest due to
information explosion that increased
dramatically in the last decade.
 Has
become more formalized that have
enabled practitioners to approach medical
problems and evaluate medical literature
with greater consistency and to deal with
massive amounts of medical information
via a qualitative approach.
EBM
Usefulness
 Instead
of routinely
reviewing the contents of
dozens of journals for
interesting articles, EBM
suggests that you target
your reading to issues
related to specific patient
problems as encountered.
 This makes EBM a life-long
self-directed and problembased learning process.
Misapprehensions &
Misinterpretations about EBM
X 1) Evidence-based medicine ignores
clinical experience and clinical intuition.
X 2) Understanding of basic investigation
and pathophysiology plays no part in
evidence-based medicine.
X 3) Evidence-based medicine ignores
standard aspects of clinical training such
as the physical examination.
Types of
Questions
(1) Background Questions
 Asked
for general knowledge about
a disorder
 Has two essentials components:
– a question root ( who, what, where,
how, why) with a verb
– a disorder
Background Questions
 Textbooks
answer background questions,
they contain collected & synthesized
wisdom for topics that do not change
often.
 Not all topics are covered, easy to use,
relatively inexpensive and can be opinionbased rather than evidence-based, written
by experts in their fields.
(2) Foreground Questions
 Asked
for specific knowledge about
managing patients with a disorder
 It has 4 components (PICO analysis):
P - Patient/Population
I - Intervention
C - Comparison
O - Outcome
 Basis
of Evidence-based care
involves the integration of the best
research evidence with clinical
expertise and patient values.
Best Clinical Evidence
Clinical
Experience
Patient’s Needs/
Preferences
Foreground
Information
Background
Information
Novice
Searcher
 At
Expert
Searcher
all stages you ask both kinds of
questions, but as experience increases
the foreground questions increase.
 It is essential that you understand the
background question before attempting to
answer the foreground ones.
EBM Principles
1. Construct a well-built clinical question
and classify it into one category (therapy,
diagnosis, etiology or prognosis)
2. Find the evidence in health care literature
3. Critically appraise or formally evaluate
for validity and usefulness
4. Integrate the evidence with patient
factors to carry out the decision
5. Evaluate the whole process
PICO ANALYSIS
 Before
attempting to
search for the
evidence in the
literature, construct a
well-built or clearly
structured question
that could be broken
into the following four
parts
(1) Patient /Population
 What
is the primary problem, disease or
co-existing conditions?
 On what groups do you want
information?
 How would you describe a group of
patients similar to the one in question?
 Sometimes age or sex of a patient may be
relevant and should be included.
– Example: post-menopausal women with
hypertension
(2) Intervention
 What
medical event do you want to study
the effect of?
 Which main intervention are you
considering, prescribing a drug, ordering
a test, ordering surgery?. . . .
– Example: ERT
(3) Comparison
 Compared
to what?
 Better or worse than no intervention at all
or than another intervention?
 What is the main alternative to compare
with the intervention, are you trying to
decide between two drugs, a drug and a
placebo, or two diagnostic tests?
 Sometimes there is no comparison.
- Example: no ERT
(4) Outcome
 What
is the effect of the intervention?
 What do you hope to accomplish,
measure, improve, or affect with this
intervention?
 What are you trying to do for the patient,
relieve or eliminate the symptoms, reduce
side effects, reduce cost? .. .
– Example: improve quality of life
What makes a clinical
question well built?
 Question
should be directly
relevant to the problem at
hand.

Question should be phrased
to facilitate searching for a
precise answer.
 Asking
a well-built question,
like many clinical skills,
needs practice.
Categories of EBM
Questions
 After
constructing the PICO analysis,
determine the category of the
question.
 There are the four categories of EBM
questions
1) Therapy
Solves questions about which treatment
to administer, and what might be the
outcome of different treatment options.
 For most therapy questions one may want
to look for the best evidence namely a
randomized controlled study, and if the
study can be a double blind, so much the
better.

- Example: find the evidence for the use of
anticoagulants in patients with atrial fibrillation
2) Diagnosis
 Solves
questions about degree to which a
test is reliable and clinically useful, to decide
whether the patient would benefit from it
 Most
articles compare result of a certain
diagnostic test with that of a standard test
regarded as being a "gold standard".
- Example: search for the best diagnostic test for
Alzheimer's disease
3) Etiology
 Solves
problems about the
relationship between a disease and
a possible cause
- Example: find out if a diet rich in saturated fats
increases the risk of heart disease, and if so by
how much
4) Prognosis

Answers questions about a patient's
future health, life span and quality of life in
the event one chooses a particular
treatment option
- Example: find how would the quality of life
change for a patient who undergoes surgery for
prostate cancer
The next step would be to determine the best study
design needed to answer the clinical question.
Types of Research Studies
 Certain
study designs are superior to others
when answering particular questions.
– RCT are considered the best for addressing
questions about therapy.
– Etiology questions may be addressed by casecontrol & cohort studies.
 Other
aspects relevant to study design include
placebo comparison group and follow-up.
1) Randomized Controlled
Trial (RCT)

Answers therapy, prevention
questions
 Randomization
selection bias
avoids
2) Cohort study
 Answers
prognosis, etiology, prevention
questions
 Cohorts are defined populations that, as a
whole, are followed in an attempt to
determine distinguishing subgroup
characteristics.
 Researchers identify and compare two
groups over a period of time.
2) Cohort study
 At
the start of the study, one of the
groups has a particular condition
or receives a particular treatment,
and the other does not.
 At the end of a certain amount of
time, researchers compare the two
groups to see how they did.
3) Case Control study
 Answers
prognosis, etiology,
prevention questions
 Identifies patients who already have
the outcome of interest and control
patients without that outcome, and
look back to see if they had the
exposure of interest or not.
4) Case series &
Case Reports
Answers prognosis, etiology,
prevention questions
 Consist either of collections of
reports on the treatment of individual
patients, or of reports on a single
patient.
