Evidence based medicine and
clinical practice
Dr. J Tumbo
Evidence-based clinical
practice

Is
an
approach
decision-making
which
the
to
in
clinician
uses the best evidence
available,
in
consultation with the
patient, to decide upon
the option which suits
that patient best.
The Evidence-based Medicine Triad
Source: Florida State University, College of Medicine.
What is EBP
• The conscientious use of current best scientific research in making
decisions regarding care of a particular patient.
• It integrates current best knowledge with practitioner’s experience
and patient values.
• It is the link between research and patient care
• Options exist of using evidence from primary studies or preappraised publications e.g. The Cochrane, Evidence that matters
Clinical Questions/situations addressed in
EBP
 Therapeutic: questions about treatment that would
be given to a patient and the treatment outcomes of
the different options
 Diagnostic: questions about the degree to which a
particular test is reliable in picking the condition
 Prognostic: questions about a patient’s future
health, lifespan and quality of life in the event that
he chooses a particular treatment option or is
affected by a specific condition
5 steps
1.
Formulate an answerable question
2.
Track down the best evidence
3.
4.
5.
Critically appraise the evidence
for validity, clinical relevance and
applicability
Individualize,
based
clinical
expertise and patient concerns
Evaluate your own performance
(clinical audit)
Assess your
patient
Ask clinical
questions
Acquire the
best evidence
Appraise the
evidence
Apply evidence
to patient care
Characteristics of answerable
question (PICO)
1.
Patient or Problem or Population – Describes your patient,
problem or population: ask “how would I describe a group of
patients similar to mine?”
2.
Intervention – Activity or process related to the patient : ask
“which main intervention am I considering
3.
Comparison intervention (if appropriate) – ask “what is the
main alternative to compare with the intervention”
4.
Outcome (s) – End result of activity or intervention: ask
“what can I hope to accomplish?”
A.
Asking the question
 The creation of a question from the clinical scenario is
the first crucial step in searching for an answer.
 It arises from a comprehensive assessment of the clinical
situation.
 Guided by clinical tasks relevant to the scenario
Example of question
What is the risk of development
of Cancer of the Breast in a 52
year old woman using
estrogen-only pills as hormone
replacement therapy.
B. Acquiring the best evidence
• Tracking down the best evidence can be manual or
computerised.
• Computerised literature search needs skill in searching.
• Needs for reliable sites e.g. PubMed
• Use of key words (not the whole question) in the search
box
• Refine the search by filters to narrow down available
literature and getting full text articles
Refining the search
 Boolean operators: conjunction words that link or exclude the key words. Common Boolean
operators include AND, OR, NOT.
 Using LIMITS to narrow the search finding. One may limit the search on the various
attributes that include “Human or animal studies”, Gender, Age, Year of publication, research
type and even the specialty

Truncating mean the use of a asterix * as suffice to part of a word that may end in multiple
ways. For example, if Bacter* is entered as a key word, the computer will search for all words
starting with bacter that include Bacteria, Bacteriology, Bacterium etc.
 Use synonyms (words which has the same meaning as another e.g. Manager and
Executive, Woman and Female).
 Related links/citations
 MESH database
What is the best evidence
Hierrhachy of evidence in
epidemiological studies
1.
Systematic reviews/meta-analysis
2.
Randomized controlled trial
3.
Cohort studies
4.
Case control studies
5.
Cross sectional studies
6.
Case report
7.
Anecdotes
Causality
Association
Descriptive
Case report/series
 Descriptive study of an experience or occurrence in
one or many individuals
Individual patients
Patient notes
Combined notes
Case report
Cross sectional study
 Descriptive study of observation or
measurement of characteristics of a defined
population at a specific point in time. No
follow-up

Population
observation
describe results
Case control study
Before exposure
disease
Hx of past exposure
Cases/controls with/out
Exposure relative to outcome
Compare histories
Draw conclusion
Cohort study
Study of group or groups with no disease in the
beginning. Exposure and follow-up is done
prospectively then measurement of outcome
Cohorts start
Outcomes
Exposure/Followup
cohort at end
Compare outcome e.g.
CANCER OF BRONCHUS
Randomised controlled trial
 Analytical study in which study participants
are randomly assigned to exposure by
researcher then followed up to identify
outcome
 Population
outcome
randomisation
exposure
followup
Compare results
Systematic review/Metanalysis
Study 1
Study 2
Combined results
Study 3
Study 4
What Is a Systematic Review?
• Systematic reviews are scientific investigations in
themselves, with an a priori protocol(pre-planned
methods) and an assembly of original studies as
their "subjects."
• They synthesize the results of multiple primary
investigations by using strategies that limit bias and
random error
What is a meta-analysis
• Enhance precision by pooling smaller studies (to
artificially create one large study)
• to arrive at a common estimate with a certain
level of certainty
Perform a search on PubMed
Subject searching
www.pubmed.gov
You are challenged by the
huge number of
pregnant women
presenting with PET.
You recall that APRIRIN
could be used to
prevent PET. However
there are differing
opinions on this. How
will you proceed
Search the Cochrane Library
International Cochrane Collaboration
>90 countries
effects of interventions
Includes:
Full-text Systematic Reviews
Abstracts to further SRs and RCTs
Available at:
http://www.thecochranelibrary.com
C. Appraisal
 Refers to the assessment of evidence by systematically
reviewing its relevance, validity and results to specific
situations.
Chambers, R. (1998). Clinical effectiveness made easy: first
thoughts on clinical governance. Oxford, Radcliffe Medical Press.
 When you search Medline, the references that you retrieve have
been published in recognised medical journals, some of which
will have been peer reviewed. The peer review process means
that the articles have been assessed by an expert in the field.
This should help to prevent poor or inaccurate research being
published. However, this does not mean that the research is
always accurate or valid. Not all research is good research.
 One of the key messages of evidence based medicine is: "Don't
believe everything you read."
Why is it important
Critical appraisal is important because it:
• ensures a comprehensive assessment of the whole paper
• allows you to identify the strengths and weaknesses of a
piece of research
• develops an improved understanding of the research
methodology used to conduct the research
• allows you to relate the published research to your local
situation
• enables you to identify any bias in the research
• facilitates the implementation of effective interventions in
your clinical practice
Process of critical appraisal
 The process of critical appraisal can be very time consuming. It
requires you to carefully read the whole article, especially the research
methodology and statistical analysis - not just the "easy" bits like the
introduction, results and conclusion sections!
 When reading an article you need to consider the following:
• Who has written the article? Are they a recognised author. Are they
affiliated to a recognised institution?
• Why? What are the aims and objectives?
• How? Has the right research methodology been used?
• When? Is it recent or seminal research?
• Where? Has it been published in a recognised journal? Is it a peer
reviewed journal?
• Do the results seem valid?
• Does the statistical evidence seem valid?
• Is there any obvious bias or conflict of interests?
• Do the conclusions stack up?
READER
Relevance
Education
Is the study relevant to answer
my Question?
Does it challenge my knowledge?
Applicability
Does it apply to my situation?
Discrimination
What is the scientific quality of the
paper?
Evaluation
What is my evaluation based on
above?
Reaction
How can I use the information?
Three questions of critical
appraisal: VIA
1. Is the study Valid?
 Discrimination & Evaluation
2. Is it Important?
 Relevance & Education
3. Is it Applicable to my patient?
 Applicability & Reaction
Question 1: Is the study valid?
 Type of study – strength of evidence
 Is the study methodology appropriate to answer the
research question?
 Was the study done properly?
Levels of evidence
What type of study would give the best evidence for each type
of question?
 Level 1a: Systematic reviews; Level 1b: Individual RCTs
with narrow confidence interval
 Level 2a & b: Cohort studies; Level 2c: Outcomes research
 Level 3a & b: Case-control studies
 Level 4: Case series & poor quality cohort /case control
studies)
 Level 5: Expert opinion
Was the study done properly?
 Sample
 Representative and appropriate
 Case-control:
 Are cases and controls
comparable
 Cohort:
 Was patients followed long
enough
 Was loss to follow-up not too
much?
 Randomised Controlled Trial:
 Double-blind
 Was randomisation done properly
 Systemic Review:
 Are all primary studies of high
quality eg randomised controlled
trials?
 Were results consistent
 Is the process explicit?
 Is synthesis accurate?
Are findings important?
 Impact/Prognosis
 P-value
 Confidence interval
 Outcome over time
 Aetiology
 Relative risk
 Odds ratio
 Significance
 Diagnosis/evaluate tests
 Compare pre- and post-test probability
 Sensitivity
 Specificity
 Predictive value
 Treatment/harm
 Numbers needed to treat/harm
 Absolute risk reduction
Is it applicable?
 Is your setting comparable to that of the study?
 Will the application of the evidence have a positive
impact on your patients?
 What are your patients preferences?
 Would it be affordable in your setting?
 What alternatives are available in your setting?
Integration into practice
• Is your patient different from those in study
• How much effect do you expect in your patients
• Are there alternatives
• Wat does the patient think?
Other sources of evidence
 WHO CHOICE (Choosing
interventions that are
cost-effective)
 WHO initiative developed
in 1998
 Reports the costs and
effects of a wide range of
health interventions in
the 14 epidemiological
sub-regions
Ten best health buys
1.
Vaccination of children against major childhood illnesses
including measles, polio, tetanus, whooping cough, and
diphtheria
2.
Monitor children’s health to prevent or, if necessary, treat
childhood pneumonia, diarrhoea, and malaria
3.
Tax tobacco products to increase consumers’ costs by at least
one-third to curb smoking and reduce the prevalence of
cardiovascular disease, cancer, and respiratory disease.
4.
Attack the spread of HIV through a coordinated approach that
includes:
 promoting 100 percent condom use among populations at high
risk
 treating other sexually transmitted infections
 providing antiretroviral medications, especially for pregnant
women
 offering voluntary HIV counselling and testing.
5. Give children and pregnant women essential nutrients including
vitamin A, iron and iodine to prevent maternal anaemia, infant
deaths, and long-term health problems
6. Provide insecticide-treated bed nets in malariaendemic areas to drastically reduce malaria
7. Enforce traffic regulations and install speed bumps at
dangerous intersections to reduce traffic-related
injuries
8. Treat TB patients with short-course chemotherapy to
cure infected people and prevent new infections
9. Teach mothers and train birth attendants to keep
newborns warm and clean to reduce illness and death
10. Promote use of aspirin and other inexpensive drugs to
treat and prevent heart attack and stroke
Resources
Cochrane Library
www.thecochranelibrary.com
PubMed
www.pubmed.gov
TRIP
www.tripdatabase.com
Other sources – CEBM web-site – EBM tools
www.cebm.net