Transcript CRITICAL APPARAISAL OF A PAPER ON THERAPY.ppt

EVIDENCE BASED MEDICINE
(EBM)
CRITICAL APPARAISAL OF A PAPER
ON THERAPY
421 CORSE
WHAT IS EBM ?
‫”قل هاتوا برهانكم إن كنتم‬
‫صادقين“‬
Clinical expertise
Research evidence
Patient preferences
EBM: THE PRACTICE
THE STEPS IN THE EBM

THE PATIENT
1. Start with the patient – a clinical
problem/question arises out of
the care of the patient.

THE QUESTION
2. Construct a well built clinical question
derived from the case.

THE SOURCE
3. Select the appropriate resource(s) and
conduct a search.

THE EVALUATION
4. Appraise that evidence for its validity
and applicability
THE STEPS IN THE EBM
(CONT….)

THE PATIENT
5. Return to the patient,
integrate that evidence
with clinical expertise,
patient preference, and
apply it in practice.

SELF EVALUATION
6. Evaluate your
performance with the
process
A WELLBUILT CLINICAL QUESTION
P
PATIENT / PROBLEM
I
INTERVENTION
C
COMPARISON
O
OUTCOME
TYPES OF STUDY
TYPES OF STUDY

EXPERIMENTAL

NONEXPERIMENTAL
THERAPUETIC STUDY

WHAT STUDY DESIGN ?
CLINICAL TRIAL
What is critical
apparaisal ?
WHAT DO WE LOOK FOR?

VALIDITY

IMPORTANCE

APPLICATION
A. Are the results Valid?
1. Was the assignment of patients to treatment Randomized?
2. Was the randomisation list concealed ?
3. Were all patients who entered the trial properly accounted
for and attributed at its conclusion? (FOLLWO UP)
A distinction:
Withdrawal: A participant in a clinical trial discontinues prescribed
treatment programe (deviates from protocol).
Dropout: A failure to measure the outcome of interest for a trial
participant at this and subsequent visits.
(80% response is accepted (less than that, should be
justified, why?)
4.Were patients analyzed in the groups to which
they were randomized ?
Intention to Treat Analysis?
The basic ITT principle is that participants in the
trials should be analysed in the groups to which
they were randomized, regardless of whether they
received or adhered to the allocated intervention

4. Were patients, their clinicians and study personnel 'blind' to
treatment?
5. Were the groups similar at the start of the trial?
Baseline prognostic factors (demographics, co-morbidity, disease
severity, other known confounders) balanced?
If different, were these adjusted for?
6. Aside from the experimental intervention, were the groups treated
equally?
Co-intervention?
Contamination?
Compliance?
B. WHAT ARE THE RESULTS?
What are the results?
1. How large is the treatment effect?
Absolute risk reduction?
Relative risk reduction?
NUMBER NEED TO TREAT?
NUMBER NEED TO HARM?
2. How precise is the estimate of the treatment effect?
Confidence intervals?
OUTCOME EVENT
TOTAL
YES
NO
EXPERIMNTAL
GROUP
a
b
a+b
CONTROL
GROUP
c
d
C+d
B.WHAT ARE THE RESULTS?
Experimental group: a b
Control group:
cd
a+b
c+d
Experimental event rate = risk of outcome event in experimental group
= EER = a/(a+b)
Control event rate = risk of outcome event in control group = CER =
c/(c+d)
Absolute risk reduction (ARR) = CER – EER
Number needed to treat (NNT) = 1/ARR = 1/(CER - EER)
Outcome
(symptomatic
Nitrofuran
cure or
tion
improvement at
day 7)
+VE
20
placebo
Total
11
31
-VE
5
14
19
Total
25
25
50
ARR= CER-EER= 11/25 - 20/25
=0.44-0.8 = 0.36
NNT= 1/ARR= 1/0.36 =2.78
===3
Will the results help me in patient care?
1. Can the results be applied to my patients?
Patients similar for demographics, severity, co-morbidity and other
prognostic factors?
Compelling reason why they should not be applied?
2. Were all clinically relevant outcomes considered?
Are surrogate endpoints valid?
3. Are the benefits worth the harms and costs?
NNT for different outcomes?
According the secondary end point of long term of
Continuous abstinence (weeks 9-26)
Stopped chewing
Didn’t stop
Total
varenicline
placebo
95
73
118
145
213
218
Total
168
263
431
Experimental event rate EER = 95/213 =
0.446
Control event rate CER = 73/218 = 0.335
Absolute risk reduction ARR = EER – CER
Absolute risk reduction ARR = 0.446  0.335
= 0.111
Number need to treat NNT = 1/ARR
Number need to treat NNT = 1/0.111
Number need to treat NNT = 9.01 ≈ 9
Results

We need to treat 9 tobacco users for 12
weeks with varenicline and follow them
up for another 14 weeks to make 1
more patient stop chewing tobacco
compared to placebo.
THANK YOU
‫بالتوفيق‬