Evidence-Based Medicine
MD. Chia-Chen Hsu
The Steps in the EBM Process
The patient
1. Start with the patient -- a clinical problem or question arises out of
the care of the patient
The question
2. Construct a well built clinical question derived from the case
The resource
3. Select the appropriate resource(s) and conduct a search
The evaluation
4. Appraise that evidence for its validity (closeness to the truth) and
applicability (usefulness in clinical practice)
The patient
5. Return to the patient -- integrate that evidence with clinical
expertise, patient preferences and apply it to practice
Self-evaluation
6. Evaluate your performance with this patient
Step 1
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Start with the patient -- a clinical problem or
question arises out of the care of the patient
A 65 y/o female patient visited our clinic with major
complaint of right anterior knee pain for six months.
She had received right TKA for 3 years.
Non-resurfacing patella was found by radiololgical
examination.
Should we resurface the patella in every TKA ?
Step 2
Construct a well built clinical question derived from the case
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Formulating Answerable Questions
形成可回答的問題
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Question components: PICO
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What types of
problem
What types of
What types of
What types of
P articipants ?
 Patient and their
I nterventions ?
C omparison ?
O utcomes ?
 Intervention
 Comparison
 Outcome
PICO
Patient or
problem
Description of
the patient or
the target
disorder of
interest
Intervention
Exposure
Diagnostic
Prognostic
factor
Therapy
Patient
perception
test
Comparison
Relevant most
often when
looking at
therapy
questions
Outcome
Clinical
outcome of
interest to
you're your
patient
Type of Question
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EBM starts with a clear clinical question
Well defined in order to be answerable
Clinical questions generally fall into
1.
2.
3.
4.
Causation / Etiology / Harm
Diagnosis / Screening
Therapy / Prevention
Prognosis / Nature history
The well-formulated question: Therapy
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People – Exposure – Comparison – Outcomes
My Question
In a 65 y/o woman with a end-stage degenerative
OA knee, could the patella resurfacing decrease
the risk of anterior knee pain after total knee
replacement ?
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In a 65 y/o woman with a OA knee, can patellar
resurfacing in TKA surgery decrease the risk of
anterior knee pain compared with non-resurfacing of
patella ?
Step 3
The resource
Select the appropriate resource(s) and conduct a search
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What is the ideal resource?
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Located in the clinical setting
Easy to use
Fast, reliable connection
Comprehensive /Full Text
Effective search engine
Provides primary data
Resources
• Colleagues
• Textbooks
– Burn your (traditional) textbooks
• Summaries of the primary evidence
– ACP Journal Club | Clinical Evidence | eMedicine | POEMs and
InfoRetriever | UpToDate
• Databases
– MEDLINE | Cochrane Library
• Electronic textbooks and libraries
– Harrisons | MD Consult | Scientific American Medicine Online |
Stat!Ref
• Meta-Search Engines
– SUMSearch | TRIP: Turning Research into Practice
Limits
Types of Studies
Patellar Resurfacing in Total Knee Arthroplasty.
A Meta-Analysis
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87:1438-1445, 2005.
J Bone Joint Surg Am.
Emilios E. Pakos, Evangelia E. Ntzani and Thomas A. Trikalinos
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Investigation performed at the Clinical Trials and Evidence-Based Medicine Unit,
Department of Hygiene and Epidemiology,University of Ioannina School of
Medicine, Ioannina, Greece, and the Institute for Clinical Research and Health
Policy Studies,Tufts-New England Medical Center, Tufts University School of
Medicine, Boston, Massachusetts
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Level of Evidence: Therapeutic Level I.
If the sole evidence you have about a treatment is
from non-randomized studies, you have five options:
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Doing another literature search
See whether the treatment effect is so huge, unethical
to randomize
Trial concluded that the treatment was useless or
harmful
“n-of-1” trial
Try to find evidence for some other treatment or simply
provide supportive care.
Randomized Trials
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A Randomized Trial is most effective in experimental studies to make
generalizations about a population because:
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Advantages:
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Randomization decreases bias from confounding factors
Blinding both the investigators and patients decreases bias.
Strong Evidence for cause and effect
Can be faster and cheaper than observational study
Disadvantages:
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Can be costly and of long duration
Ethical issues may prevent experimentation
Disease may be too rare
Study intervention may be too different from common practice
Tend to restrict scope and narrow the study question
Patellar Resurfacing in Total Knee Arthroplasty
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Background:
Patellar resurfacing during total knee arthroplasty remains
controversial. We aimed to evaluate the effectiveness of this
technique through an evaluation of the current literature.
Methods:
We performed a meta-analysis of randomized controlled trials
comparing total knee arthroplasties performed with and without
patellar resurfacing. Outcomes of interest included the number of
reoperations, the prevalence of postoperative anterior knee pain,
and the improvement in various knee scores.
Materials and Methods
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Searched MEDLINE, EMBASE, and the Cochrane
Central Register of Controlled Trials for randomized
trials comparing total knee arthroplasties performed
with and without patellar resurfacing;
References of retrieved articles were also screened.
no language restrictions.
regardless of the indication for total knee arthroplasty,
the surgical technique, or the specific type of
prosthesis used.
the risk of reoperation in knees with resurfaced and nonresurfaced
patellae
the risk of reoperation according to the duration of
follow-up
The risk of postoperative anterior knee pain
Patellar Resurfacing in Total Knee Arthroplasty
Results1:
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Ten trials assessing 1223 knees were eligible.
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The absolute risk of reoperation was reduced by 4.6% (95% confidence
interval, 1.9% to 7.3%) in the patellar resurfacing arm (between-study
heterogeneity, p < 0.01; I2 = 60%),implying that one would have to
resurface twenty-two patellae (95% confidence interval, fourteen to fiftytwo patellae) in order to prevent one reoperation.
(NNT= 1/ARR = 1/ 4.6% = 21.7)
Patellar Resurfacing in Total Knee Arthroplasty
Results 2:
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Patellar resurfacing reduced the absolute risk of postoperative anterior
knee pain by 13.8% (95% confidence interval, 6.4% to 21.2%), implying
that one would have to resurface seven patellae (95% confidence
interval, five to sixteen patellae) in order to prevent one case of
postoperative anterior knee pain.
(NNT= 1/ 13.8% = 7.24)
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Only four trials provided adequate data for a quantitative synthesis of the
changes in the various knee scores; on the basis of those four trials,
there was no difference in the mean improvement in the knee scores
(standardized mean difference, 0.03; 95% confidence interval, −0.50 to 0.56).
Conclusions
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The available evidence indicates that patellar resurfacing
reduces the risks of reoperation and anterior knee pain after
total knee arthroplasty.
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The observed effects are clinically important despite their
modest magnitude.
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Additional, carefully designed randomized trials are required
to strengthen this claim.