Introduction to
Evidence-Based Medicine
Bill Cayley Jr MD MDiv
UW Health Augusta Family Medicine
Objectives
1. Describe the use of evidence in making
medical decisions
2. Demonstrate searching for an evidencebased answer to a medical question
What is
“evidence-based
medicine?”
Two fundamental questions…
• What is the purpose of medicine?
• How do I decide what to do?
You have to know where you’re going before
deciding how to get there…
What is the purpose of medicine?
• Patient care
• Public health
• Research
 Improving the quality of
patients’ lives…
What is evidence-based medicine?
Evidence based medicine is the conscientious,
explicit, and judicious use of current best
evidence in making decisions about the care of
individual patients.
Sackett, et al. BMJ 1996;312:71-72
What is “EBM” NOT?
• What we have always
done
• “Cookbook medicine”
• Only a cost-cutting trick
• Only randomized trials
Evidence based medicine IS…
 Tracking down the best
external evidence with which
to answer our clinical
questions…
EBM – a short history…
• JAMA 1992
“EBM: a new approach…”
• JAMA 1993 – 2000
“Users' Guides to the
Medical Literature”
• 1990s – 3 trends
– Systematic reviews
– Search engines
– Knowledge distillation
and “push” services
Classification of evidence
How do I decide what to do?
How do I make decisions?
• Dogma: “Natural is best”
• Tradition: “We’ve always done it that way”
• Convention: “Everyone does it this way”
• Evidence-Based: “Evidence supports this way”
How do I decide what to do?
 The answer from EBM…
“…use of current best
evidence…”
Evidence: systematic observation
Meta-Analysis
Randomized Controlled Trial
Uncontrolled Trial
Case Series
Anecdote
Meta-Analysis
Randomized Controlled Trial
Uncontrolled Trial
Case Series
Anecdote
More systematic observation ► better evidence
Integrating evidence & practice
What type of outcome measures?
• Surrogate markers of disease:
– Hb A1c, cholesterol, blood pressure
• Stage or extent of disease:
– Diabetic ulcers, angiographic CAD, stroke
• Patient-oriented outcomes:
– Mobility, suffering, longevity
– Morbidity and mortality
Patient or disease oriented?
• Disease-Oriented Outcomes.
– Intermediate, histopathologic, physiologic, or surrogate
results
– Examples: blood sugar, blood pressure, flow rate, coronary
plaque thickness
– May or may not reflect improvement in patient outcomes.
• Patient-Oriented Outcomes.
– Outcomes that matter to patients and help them live
longer or better lives
– Examples: including reduced morbidity, reduced mortality,
symptom improvement, improved quality of life, or lower
cost
Which outcomes????
• Topical antibiotics for bacterial conjunctivitis may improve
early and late resolution rates, but nearly all cases ultimately
have complete remission.
• Br J Gen Pract. 55: 962-4.
• Digoxin for symptomatic heart failure provides no significant
difference in mortality but is associated with lower rates of
hospitalization and of clinical deterioration.
• J Card Fail. 10:155-64.
• Long-acting beta-2 agonists for asthma are effective in
reducing symptoms but may increase mortality or
exacerbations.
• Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD006363.
SORT
When guidelines conflict…
Questions of evidence
• Were the clinical questions
different?
• Were different studies
considered?
• Were the results analyzed
differently?
• Was the quality of evidence
assessed differently?
Questions of outcomes
• Did the effect estimates for
important outcomes differ?
• Did judgments about
evidence quality differ?
• Were health consequences
weighed differently?
• Were economic
consequences considered
differently?
Systems applications
Clinical Questions
• Background - “What is it?”
– General information on a condition or disease
• Foreground – “What do I do for this patient?”
– Patient
– Intervention/Investigation
– Comparison Intervention/Investigation
– Outcome (Patient-Oriented)
Clinical Questions - “PICO”
Example:
• In a 5 year old child with conjunctivitis (patient) will
topical antibiotics (intervention) compared to no
treatment (comparison) lead to quicker symptom relief
(outcome)?
• In a 5 year old child with conjunctivitis (patient) will
topical antibiotics (intervention) compared to no
treatment (comparison) lead to improved cure rates
(outcome)?
Finding Evidence-based Answers
• Trip Database (http://www.tripdatabase.com/)
• Database of Abstracts of Reviews of Effectiveness
(http://www.crd.york.ac.uk/crdweb/)
• DynaMed (http://www.dynamicmedical.com/)
– *Subscription required.
• Essential Evidence Plus (http://www.essentialevidenceplus.com/)
– *Subscription required.
• Cochrane Library (http://www.cochrane.org/)
– *Subscription for full access, abstracts free.
• FPIN (http://www.fpin.org/)
– *Subscription required.
• Clinical Evidence (www.clinicalevidence.com/)
– *Subscription required.
For further reading…
• Woolever DR. The art and science of clinical decision making. Fam Pract
Manag. 2008 May;15(5):31-6. PMID: 18546805
(http://www.aafp.org/fpm/20080500/31thea.html)
• Krumholz H, Lee T. Redefining Quality -- Implications of Recent Clinical
Trials. N Engl J Med 2008 358: 2537-2539
(http://content.nejm.org/cgi/content/full/358/24/2537)
• Ebell MH. How to find answers to clinical questions. Am Fam Physician.
2009 Feb 15;79(4):293-6. PubMed PMID: 19235495.
(http://www.aafp.org/afp/2009/0215/p293.html)
In short…
 EBM is the conscientious,
explicit, and judicious use of
current best evidence in
making decisions about the
care of individual patients.
Patient-oriented evidence
preferable to
Stage of disease
preferable to
 Evidence
Systematic observation =
high-quality evidence
Surrogate markers