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evidence-based medicine (EBM)*:
what it is & why its necessary
Rod Jackson 2013
* also called evidence-based
practice (EBP)
evidence-based medicine (EBM)*:
what it is?
‘its about how to better inform your
clinical decisions with the best up-todate epidemiological evidence’
core components of ‘traditional’
evidence based decision-making
patient’s
system:
values &
policy /
preference regulation /
s
resources
patient’s
clinical
status*
*relied on clinical knowledge or ‘mechanistic evidence’ mainly from:
anatomy, physiology, pathology, biochemistry, psychology, etc.
‘modern’ EBM explicitly emphasises ‘current’
best clinical epidemiological evidence about
outcomes directly relevant to people
values/prefer
ences
evidence
from
epidemiology
system issues
patient’s
clinical status
mechanistic
evidence
evidence from direct observation, what happens in practice
clinical epidemiological evidence*
• how accurate are diagnostic tests?
• how strong are prognostic markers?
• how effective are interventions?
– therapy
– Screening
– prevention
* study of the probability of outcomes in groups of patients
Aristotle (384 – 322 BCE): the first
evidence based practitioner?
None of the arts (i.e sciences) theorise about individual cases.
Medicine, for instance, does not theorise about what will help to
cure Socrates, but only about what will help to cure any or all of a
given class of patients. This alone is our business. Individual cases
are so infinitely various that no systematic knowledge of them is
possible.
Aristotle. Rhetoric. book I, chapter 2: 1356b
(clinical epidemiology is the science of investigating the
probability of outcomes in ‘groups ‘or classes’ of patients’)
evidence-based practice
‘informing decisions more explicitly with the best
up-to-date evidence, particularly from
epidemiology’
by using this evidence:
• more efficiently
• more critically
• more systematically
EBP: informing decisions with the best up-to-date evidence
why do we need to use evidence efficiently?
Articles
Per
Medical
Articles
perYear
Year
2500000
5,000?
per day
2000000
1500000
2,000
per day
1000000
75 per
day
500000
0
Biomedical
MEDLINE
Trials
Diagnostic?
EBP: informing decisions with the best up-to-date evidence
clinical evidence increasing so rapidly we need better skills
to keep up-to-date more efficiently than previous
generations of clinicians
more efficiently
Bastian, Glasziou, Chalmers PLoS 2010 Vol 7 | Issue 9 | e1000326
using evidence more critically
validity: most articles should be ignored
EBM Journal Process
• 140+ journals scanned
Number Needed to Read
to find 1 valid is 20+
– 60,000 articles
• Is it valid? (<5%)
– Intervention: RCT
– Prognosis: inception cohort
– Etc
• Is it relevant?
– 6-12 GPs & specialists asked:
Relevant? Newsworthy?
• < 0.5% selected
more critically
Number Needed to Read
to find 1 valid & relevant is 200+
EBP: informing decisions with the best up-to-date evidence
but many clinicians cannot tell good
from poor quality research
BMJ study of 607 reviewers
– 14 deliberate errors inserted
Detection rates
–
–
–
–
On average <3 of 9 major errors detected
Poor Randomisation (by name or day) - 47%
Not intention-to-treat analysis - 22%
Poor response rate - 41%
Schroter S et al, accepted for Clinical Trials
more critically
EBP: informing decisions with the best up-to-date evidence
using evidence more systematically
Total mortality from trials of βblockers in 2° prevention after
MI.
Black square & horizontal line
correspond to odds ratio (OR) &
95% confidence interval (CI) for
each trial. The size of the black
square reflects the weight of each
trial. The diamond represents the
combined OR & 95 CI, showing a
22% reduction in odds of death
Egger, M. et al. BMJ 1997;315:1533-1537
using evidence more systematically
Cumulative metaanalysis of total
mortality results from
trials of oral β-blockers
after MI.
Size of squares reflect
amount of statistical
information available at a
given point in time
Egger, M. et al. BMJ 1997;315:1371-1374
Gets worse with “duration in practice”
what skills will you need to keep
up to date with the best
evidence?
• to find the evidence more efficiently
• to appraise the quality of the evidence
more effectively
• to use good quality evidence more
systematically
the steps of practicing EBM
1. ask a focused question.
2. access (systematically search for) epidemiological
evidence to help answer question.
3. appraise evidence found for its validity, effect size,
precision (ideally all the relevant evidence)
4. apply the evidence in practice:
a. amalgamate the valid evidence with other relevant
information (values & preferences, clinical/health issues,
& system issues) and make an evidence-based decision;
and
b. act (implement) the decision in practice
explicitly improving practice with external evidence from literature
about 1/2 of ‘valid’
evidence today is out of
date in 5 years
about 1/2 of valid
evidence is not
implemented
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the 5th step of EBP = Quality Improvement
5. audit your practice:
compare your actual practice with best (evidencebased) practice
i.e. the gap between your evidence-based decisions
and your actions
explicitly improving practice with internal evidence from your practice
GATE: Graphic Approach To Evidence Based Practice
- a framework for learning the skills of EBP
1 picture, 2 formulas & 3 acronyms
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