Transcript Workshop on Evidence-based Health Care and the Cochrane

Evidence-based
Practice (EBP)
The What, the Why and the How
J. Irlam, Prof J. Volmink
Primary Health Care Directorate
UCT Faculty of Health Sciences
April 2005
Adapted from a presentation by the South African
Cochrane Centre, MRC
Outline of lecture
Definition of EBP
 Four Lessons from History
 Challenges of the Information Age
 How can EBP help?
 Concluding comments

Intro to EBP 2005
Evidence-based
Practice is..
“..the conscientious, explicit and
judicious use of the current best
evidence in making health care
decisions”
Sackett DL, Richardson WS, Rosenberg W, Haynes RB.
Evidence-based Medicine. 1997
Intro to EBP 2005
Why do we need to
learn this stuff?

To be able to identify, appraise and apply
best evidence in making health care
decisions

To be able to continually appraise and
assimilate new scientific evidence so as
to remain up-to-date with new
developments in medical knowledge and
practice
(UCT MBChB Graduate profile: Core Competencies)
Intro to EBP 2005
The need for EBP
“Perhaps the most important issue facing
the health care service is not how it
should be organised or financed, but
whether the care it provides actually
works.”
Bandolier, 1997
Intro to EBP 2005
Four Lessons
from History..
Intro to EBP 2005
Lesson 1
Distinguish between medical
ritual and evidence-based
practice
e.g. Optimal number of antenatal visits
Intro to EBP 2005
Lesson 2
What’s good in theory MUST be
tested by sound research
e.g. DES hormone to prevent
complications of pregnancy
Intro to EBP 2005
Lesson 3
Clinical experience is necessary
but not sufficient for making good
clinical decisions
e.g. anti-arrhythmic drugs after heart attack
Intro to EBP 2005
Lesson 4
Focus on outcomes that are
important to patients rather than
on surrogate endpoints
e.g. anti-arrhythmic drugs after heart attack
Intro to EBP 2005
Challenges of
the Information
Age..
Intro to EBP 2005
The Information
Explosion

Journals
– over 30 000 biomedical journals
– over 2 million articles per year

Textbooks

Grey literature

MEDLINE: over 14 million citations (Dec. 03)

Worldwide Web
Intro to EBP 2005
Intro to EBP 2005
Recent health news


“Too much sleep makes you fat,
say scientists”
“Some flab is fab, says new
obesity study”
 “Daycare may ward off leukaemia”
Intro to EBP 2005
Who do you believe?
Intro to EBP 2005
How can EvidenceBased Practice
help?
Intro to EBP 2005
Steps towards EvidenceBased Practice
The Five A’s
1. Ask the right question
2. Access the relevant evidence
3. Appraise the evidence
– valid? clinically important?
4. Apply the evidence to patient care
– feasible? acceptable?
5. Assess clinical practice regularly
Intro to EBP 2005
1. Ask the right
question
DEFINE:
Population
Intervention/ Exposure
Comparison group
Outcomes
Intro to EBP 2005
Case scenario 1:
to immunise or not to immunise?
John is an infant. His parents seek
your advice about the risk of severe
adverse reactions to the pertussis
vaccine.
Intro to EBP 2005
Case scenario 1
What is the clinical question?

POPULATION: Infants

INTERVENTION: Pertussis vaccine

COMPARISON: Non-pertussis/ placebo vaccine

OUTCOME: Severe adverse reactions

Does the pertussis vaccine increase the
risk of severe adverse reactions in infants
compared to no or other vaccines?
Intro to EBP 2005
Case scenario 2
Vasectomy and testicular cancer
George has come to discuss the possibility
of getting a vasectomy. He says he has
heard something about vasectomy causing
an increase in testicular cancer later in life.
You know that the risk of this is low but want
to give him a more precise answer.
Intro to EBP 2005
Case scenario 2
What is the clinical question?
Population
=
adult males
Intervention
=
vasectomy
Comparison
=
no vasectomy
Outcome
=
testicular cancer

Does vasectomy increase the risk of
testicular cancer in adult males compared
to no vasectomy?
Intro to EBP 2005
2. Access the evidence

Cochrane Library
– Database of Systematic Reviews (CDSR)
– Database of Abstracts of Reviews of Effects
(DARE)
– Central Register of Controlled Trials
(CENTRAL)

MEDLINE (PubMed Clinical Queries)
– Systematic Reviews
– Clinical Queries using Research Methodology Filters
Intro to EBP 2005
Intro to EBP 2005
3. Appraise the evidence - 1
Best
Worst

Systematic reviews

Randomised controlled trials (RCT)

Observational studies (cohort, casecontrol, cross-sectional)

“Expert” opinions, based on clinical
evidence, descriptive studies, or
reports of expert committees

Anecdote: ”Someone once told
me…”
Intro to EBP 2005
3. Appraise the evidence - 2
Is the study design appropriate to the question?

What are the risk factors for this condition?
 Cohort Study or Case-Control Study

Is the diagnostic / screening test valid?
 Cross sectional (validation) studies

What is the best intervention?
 Randomised controlled trials (RCTs)

What is the prognosis ?
 Cohort Study or Case-Control Study
Intro to EBP 2005
3. Appraise the evidence - 3
I. Are the results of the study valid?

Could the results be due to bias?

Could the results be due to
confounding?

Could the results be due to chance?
Intro to EBP 2005
Critical appraisal and
causal inference
NO
Could it be due to selection
or measurement bias?
Could it be due
to confounding?
NO
Observed association
Apply guidelines and
make judgment
Could it be the
result of chance?
NO
NO
Could it be causal?
Intro to EBP 2005
3. Appraise the evidence - 4
II. What are the results?
Are they large enough ..
(As measured by the relative risk, absolute risk,
or odds ratio)
and precise enough ..
(As measured by the confidence interval or pvalue)
and clinically relevant?
(As measured by the Number Needed to Treat
(NNT)
Intro to EBP 2005
Which screening programme would
you fund?

Programme A reduced the risk of breast cancer
deaths by 34%

Programme B produced an absolute reduction in
breast cancer deaths of 0.06%

Programme C meant that 1592 women needed to
be screened to prevent 1 death from breast cancer

Programme D increased the proportion of patients
surviving breast cancer from 99.82% to 99.88%
Intro to EBP 2005
4. Apply the evidence
III. How relevant are the results to my
patient?

Were the study participants sufficiently different
from my patient that the results don’t apply?

Is the treatment feasible in my setting?

What are the potential benefits and harms to my
patient from the intervention?

Are my patient’s values and preferences satisfied
by the intervention and its consequences?
Intro to EBP 2005
5. Assess your clinical
practice regularly
• How good am I in asking answerable
clinical questions?
• How successful am I in getting answers
to these questions?
• Do I critically appraise the evidence?
• How well am I applying the evidence in
my practice?
Intro to EBP 2005
In Conclusion..
Intro to EBP 2005
EBP is a systematic approach to using
evidence for better patient care
1. Asking the right questions
2. Accessing the relevant evidence
3. Appraising the evidence
–
valid? clinically important?
4. Applying evidence to patient care
–
feasible? acceptable?
5. Assessing clinical practice regularly
Intro to EBP 2005
EBP is about integrating
evidence with clinical expertise
“The practice of evidence based
medicine means integrating individual
clinical expertise with the best available
external clinical evidence from
systematic research.”
BMJ 1996;312:71-72
Intro to EBP 2005
The potential of EBP

Improves continuity and uniformity of care

Provides a structure for effective teamwork

Provides a common structure for problemsolving and communication

Promotes better use of resources
Rosenberg, Donald. BMJ 1995; 310:17-25
Intro to EBP 2005
The difficulties of EBP
“The notion that right-minded people will naturally
make decisions on the basis of the best available
scientific evidence is a misleading and dangerous
idea”
Erve Chambers, 1985
“The presumption is made that the practice of medicine
was previously based on a direct communication with
God or by tossing a coin.”
Fowler, Lancet 1995;346:823
Intro to EBP 2005
For the best
quality
health care,
use of the
best
available
evidence is
essential
Intro to EBP 2005