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Critical appraisal: Randomized-controlled trials for Drug Therapy

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Critical appraisal: Randomized-controlled trials for Drug Therapy Nancy J. Lee, PharmD, BCPS Research fellow, Drug Effectiveness Review Project Oregon Evidence-based ... – PowerPoint PPT presentation

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Title: Critical appraisal: Randomized-controlled trials for Drug Therapy


1
Critical appraisalRandomized-controlled trials
for Drug Therapy
Nancy J. Lee, PharmD, BCPS Research fellow, Drug
Effectiveness Review Project Oregon
Evidence-based Practice Center Oregon Health and
Science University To receive 1.0 AMA PRA
Category 1 Credit you must review this section
and answer CME questions at the end. Release
date January 2009 Expiration date January
2012
2
Attachments
  • The attachments tab in the upper right hand
    corner contains documents that supplement the
    presentation
  • Handouts of slides and a glossary of terms can be
    found under this tab and are available to print
    out for your use
  • URL to online resources are also available

3
Program funding
This work was made possible by a grant from the
state Attorney General Consumer and Prescriber
Education Program which is funded by the
multi-state settlement of consumer fraud claims
regarding the marketing of the prescription drug
Neurontin.
4
Continuing education sponsors
The following activity is jointly sponsored
by The University of Texas Southwestern Medical
Center and the Federation of State Medical
Boards Research and Education Foundation.
5
CME information
Program Speaker/Author Nancy J. Lee, PharmD,
BCPS Research fellow, Oregon Health and
Science University, Oregon Evidence-base
Practice Center, Drug Effectiveness Review
Project Course Director Barbara S.
Schneidman, MD, MPH Federation of State
Medical Boards Research and Education Foundation,
Secretary Federation of State Medical
Boards, Interim President and Chief Executive
Officer Program Directors David Pass,
MD Director, Health Resources Commission,
Oregon Office for Health Policy and Research
Dean Haxby, PharmD Associate Professor
of Pharmacy Practice, Oregon State University
College of Pharmacy Daniel Hartung,
PharmD, MPH Assistant Professor of
Pharmacy Practice, Oregon State University
College of Pharmacy
Target Audience This educational activity is
intended for those that are involved with
committees involved with medication use policies
and for health care professionals who are
involved with medication prescribing. Educational
Objectives Upon completion of this activity,
participants should be able to recognize
differences between critical appraisal and
quality assessment /internal validity review the
general steps involved in critical appraisal
discuss various components of internal validity
to review important statistical concepts
important in critical appraisal recognize
importance of clinical insight and experience in
critical appraisal.
6
CME policies
Accreditation This activity has been planned and
implemented in accordance with the Essential
Areas Policies of the Accreditation Council for
Continuing Medical Education through the joint
sponsorship of The University of Texas
Southwestern Medical Center and the Federation of
State Medical Boards Research and Education
Foundation. The University of Texas Southwestern
Medical Center is accredited by the ACCME to
provide continuing medical education for
physicians. Credit Designation The University
of Texas Southwestern Medical Center designates
this educational activity for a maximum of 1.0
AMA PRA Category 1 Credit. Physicians should
only claim credit commensurate with the extent of
their participation in the activity. Conflict
of Interest It is the policy of UT Southwestern
Medical Center that participants in CME
activities should be made aware of any
affiliation or financial interest that may affect
the authors presentation. Each author has
completed and signed a conflict of interest
statement. The faculty members relationships
will be disclosed in the course
material. Discussion of Off-Label Use Because
this course is meant to educate physicians with
what is currently in use and what may be
available in the future, off-label use may be
discussed. Authors have been requested to inform
the audience when off-label use is discussed.

7
DISCLOSURE TO PARTICIPANTS
It is the policy of the CME Office at The
University of Texas Southwestern Medical Center
to ensure balance, independence, objectivity, and
scientific rigor in all directly or jointly
sponsored educational activities. Program
directors and speakers have completed and signed
a conflict of interest statement disclosing a
financial or other relationship with a commercial
interest related directly or indirectly to the
program. Information and opinion offered by the
speakers represent their viewpoints. Conclusions
drawn by the audience should be derived from
careful consideration of all available scientific
information. Products may be discussed in
treatment outside current approved
labeling. FINANCIAL RELATIONSHIP
DISCLOSURE Faculty
Type of
Relationship/Name of Commercial
Interest(s) David Pass, MD None Dean Haxby,
PharmD Employment/CareOregon Daniel Hartung,
PharmD, MPH None Nancy Lee, PharmD,
BCPS None Barbara S. Schneidman, MD,
MPH None
8
Learning objectives
  • Recognize difference between overall critical
    appraisal of evidence and quality assessment /
    internal validity
  • What is it and why is it necessary?
  • Review general steps involved in critical
    appraisal
  • Discuss various components of internal validity
  • Review important statistical concepts important
    in critical appraisal
  • Recognize importance of clinical insight and
    experience in critical appraisal

9
What is critical appraisal?
  • Process of examining research evidence to
    evaluate its validity, results, and relevance
    before making an informed decision
  • Its not an exact science and it wont give us
    the right answers
  • Foundation to practicing thoughtful
    evidence-based or evidence-informed medicine

10
Why is it necessary?
  • Not all publications are equally convincing or
    reliable (even if published in a reputable
    journal).
  • Incorrect interpretation
  • Fraud and misrepresentation of results
  • Data dredging
  • Data dumping
  • Sometimes clinical experience and theory based on
    pathophysiology can be misleading.
  • Systematically examining the literature increases
    our confidence in our strengths and shed light on
    areas of weakness

11
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12
Benefits and challenges
  • Benefits
  • Encourages objective assessment of the literature
  • Recognize breadth and depth of evidence base in a
    particular topic area
  • Challenges
  • Time intensive at first
  • Generates more questions than answers
  • Potential to highlight lack of good evidence
    making decision making challenging

13
Critical appraisal requires that you ask yourself
  1. Is this relevant?
  2. Is this valid?
  3. Is this reliable?
  4. Is this important and meaningful?
  5. Is this applicable or generalizable?

14
1. Is this article even relevant?
  • Should I read it?
  • Title
  • Abstract
  • Introduction
  • Does this study identify a gap in the evidence?
  • Were the objectives clear and focused?
  • Should I continue?
  • Methods
  • Were inclusion and exclusion criteria clearly
    stated?
  • Are the outcomes patient-oriented or surrogate
    markers for long-term health outcomes?
  • How long was the study? (study duration)

15
2. Is this valid?
  • INTERNAL validity or study quality
  • Was the design, methods, and conduct of a study
    likely to have prevented or minimized bias in
    such a way that I can trust the findings?
  • With the information provided, could I reproduce
    this study and observe similar findings?

Trust no one unless you have eaten much salt
with him. -Cicero Skepticism is the
chastity of the intellect -George Santayana
16
A few words about quality
  • Means different things to different people
  • In the context of this module, quality refers
    to methodologic quality or
  • Study quality quality assessment internal
    validity
  • NOT the same as quality of reporting
  • Remember not reported ? not performed
  • Sometimes difficult to differentiate between the
    two
  • Subjective processmay use dual review

17
Threats toINTERNAL validity
Selection bias,
Performance bias,
Detection bias,
Attrition bias
  • Randomization
  • Allocation concealment
  • Blinding
  • Attrition
  • Statistical analysis
  • Other
  • Post-randomization exclusions
  • Crossovers
  • Contamination

18
Is this valid? INTERNAL validity
  • Randomization
  • Adequate (unbiased) computerized random number
    generator, random number table
  • Inadequate (biased) by hospital number, date of
    birth, alternate assignment
  • Allocation concealment
  • Adequate (unbiased) interactive voice response
    system, sealed, opaque envelopes that are coded
    and handled by a third party (centralized or
    pharmacy-controlled)
  • Inadequate (biased) serially numbered envelopes
    (even sealed opaque envelopes can be subject to
    manipulation), open lists

Were both treatment groups fairly balanced?
19
Example
Primary outcome cardiovascular events or deaths
Tolbutamide N 204 ( of subjects) Placebo N 205 ( of subjects)
Age gt55 50 41
Digitalis use 8 5
Angina 7 5
ECG abnormality 4 3
Total chol gt300 mg/dL 15 9
Fasting glucose gt110 mg/dL 72 64
Hypertension 30 37
20
Is this valid? INTERNAL validity
  • Blinding
  • Single-blind, double-blind, triple-blind,
    open-label, double-dummy
  • Who was blinded?
  • Was blinding maintained?
  • Is blinding essential or possible in every
    situation?
  • Important when outcome measures involve some
    subjectivity
  • May be less important when outcome measure is
    death

Therapy administered in the comparator arm should
be as identical to the therapy administered in
the treatment arm
21
Examples
  • Aspirin 1 gram vs. placebo post-MI
  • Double-blind
  • Risk of bleeding?
  • Ascorbic acid 1 gram vs. placebo for the common
    cold
  • Double-blind
  • Taste difference?
  • Esomeprazole vs. Omeprazole for erosive
    esophagitis
  • Double-dummy
  • Appearance?

22
Is this valid? INTERNAL validity
  • D. Attrition
  • Was the total number of participants who withdrew
    reported for each group?
  • Were reasons for withdrawal provided?
  • Includes adverse events, lost to follow-up,
    protocol violation, or lack of efficacy

23
Is this valid? INTERNAL validity
  • Commonly reported methods of analysis
  • Intention-to-treat
  • Always verify the numbers yourself
  • Practical issue depending on the reason behind
    the missing data, may allow for lt3-5 difference
    in baseline ITT numbers.
  • Other popular approaches last observation
    carried forward (LOCF), as-treated or
    Per-protocol analyses, data not imputed, mixed
    modeling, etc.

24
Is this valid? INTERNAL validity
  • E. Statistical analysis
  • Was the method appropriate?
  • What is the potential for type I or type II
    error?
  • Adequate power?
  • False positive
  • False negative
  • Selective analysis of data ? selective reporting
  • Example calculating statistical significant
    p-value for A1c at week 26 instead of week 52

25
Is this valid? INTERNAL validity
  • F. Other
  • - Post-randomization exclusions,
    crossovers, contamination?
  • Were any groups of participants excluded during
    the course of study?
  • Why? Was this significant?

26
Is this valid? For Harms
  • Apply similar concepts and also ask
  • How was harms monitored?
  • Active or passive methods?
  • Who assessed the harms?
  • Study investigator or third party?
  • When and how often were the assessments
    conducted?
  • Face-to-face or over the phone?
  • Various terms used
  • Safety fading out (except with FDA)
  • Adverse effect undesirable outcome with
    reasonable causal association
  • Adverse event undesirable outcome with unknown
    causal association
  • Tolerability ability or willingness to tolerate
    unpleasant drug-related events without serious or
    permanent sequelae

27
Tools for assessing internal validity
  • There are gt 25 different scales and tools for
    assessing the internal quality of a trial
  • Jadad scale
  • Chalmers scale
  • Cochrane Risk of Bias tool
  • DERP method
  • Adapted from US Preventative Task Force (USPTF)
    and National Health Service Centre for Reviews
    and Dissemination (UK)

28
Example Jadad scale
Item Score
1. Was the study described as randomized? 0 or 1
2. Was the method used to generate the sequence of randomization described and was it appropriate (ie, computer generated, table of random numbers)? 0 or 1
3. Was the study described as double-blind? 0 or 1
4. Was the method of double-blinding described and was it appropriate? 0 or 1
5. Was there a description of withdrawals and dropouts? 0 or 1
Deduct 1 point if the method used to generate the sequence of randomization was described but inappropriate (ie, allocated alternately or according to date of birth or hospital number)? 0 or -1
Deduct 1 point if the study was described as double-blind but the method of blinding was inappropriate (ie, comparison of tablet vs. injection without a double dummy)? 0 or -1
Scoring range 0-5 Poor quality lt3
29
Example Cochrane Risk of bias tool
http//www.ohg.cochrane.org/forms/Risk20of20bias
20assessment20tool.pdf
30
Example DERP method
Author
Author
31
Example
32
  1. Is this relevant?
  2. Is this valid?
  3. Is this reliable?
  4. Is this important and meaningful?
  5. Is this applicable or generalizable?

33
3. Are the results reliable?
  • Were all the results reported?
  • Was there evidence of selective outcome
    reporting?
  • How were the results reported? And are they easy
    to read or determine?
  • How large is the treatment effect?
  • Relative risk, relative risk reduction, odds
    ratio, absolute risk reduction, number needed to
    treat
  • How precise is the estimate of the effect?
  • How narrow or wide is the confidence interval?
  • Where does the point estimate fall?

34
Do not put your faith in what statistics say
until you have carefully considered what they do
not say.  -William Watt
  • Brief overview of
  • Relative risk
  • Odds ratio
  • Absolute risk
  • Number needed to treat
  • P-value
  • Confidence intervals

35
Is this reliable? Interpreting data
  • Relative risk (RR) event rate or risk ratio
  • RR 1 (no difference)
  • RR lt 1 (intervention lowers the risk of the
    outcome)
  • RR gt 1 (treatment increases the risk of the
    outcome)
  • Relative risk reduction (RRR)

36
Limitations of risk ratios
  • Study 1 (outcome) death from any cause
  • Treatment 1
  • Placebo 2
  • RR 0.50 and RRR 50
  • Study 2 (outcome) death from any cause
  • Treatment 25
  • Placebo 50
  • RR 0.50 and RRR 50

37
Is this reliable? Interpreting data
  • Odds for an event within a single group
  • Odds ratio compares the odds across groups
  • OR 1 (no difference)
  • OR lt 1 (lowers the odds of experiencing the
    outcome)
  • OR gt 1 (increases the odds of experiencing the
    outcome)

38
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39
Is this reliable? Interpreting data
  • Absolute risk reduction or Risk difference
  • Number needed to treat to benefit or harm
  • Should include duration of follow-up and the
    control group event rate

40
Example
New Antiplatelet for Patients with Acute
Myocardial Infarction Conclusion The new
antiplatelet medication (MiHaart) for acute
myocardial infarction is more effective than
placebo with a 25 reduction in mortality after
60 days of treatment.
Mortality ( events)
Placebo (N1000) MiHaart (N1000)
Composite 250 187.5
High risk patients 200 150
Low risk patients 50 37.5
41
Crunching the numbers
Mortality ( events)
Placebo (N1000) MiHaart (N1000)
Composite 250 187.5
High risk patients 200 150
Low risk patients 50 37.5
Risk MiHaart 187.5/1000 0.1875 Placebo
250/1000 0.250 Relative risk MiHaart
0.1875 0.75 Placebo 0.250 Relative
risk reduction 1- 0.75 x 100 25
Absolute risk (rate) MiHaart 18.75 Placebo
25.0 Absolute risk reduction 25.0 - 18.75
6.25
42
Crunching the numbers
RR RRR ARR NNT
Composite 0.75 25 6.25 16
High risk patients 0.75 25 5 20
Low risk patients 0.75 25 1.25 80
RR and RRR tend to provide inflated magnitude of
effect compared with the ARR but in order to
determine if any of these values is a good point
estimate of mortality, we must evaluate the
confidence interval in which it lies.
43
Is this reliable? Interpreting data
  • How can we determine if the point estimate is a
    good reflection of the true value?
  • The utility of the P-value
  • Role of the confidence interval (CI)

44
The P-value
  • Used to measure statistical significance in
    epidemiology.
  • By convention, p-value typically set at 0.05 (?)
    assumes that an event at a rate 1 in 20 is
    unlikely to be due to random chance alone.
  • The smaller the p-value, the more unlikely the
    point estimate was due to random chance.
  • Does not provide the possible range of the true
    differences of the point estimate

45
The problem with P-values
  • P-values do not give indication of
  • Treatment effect size
  • Precision of estimate
  • Direction of effect
  • Degrades data measures into dichotomous judgments
  • Significant (Plt0.05)
  • Not Significant (Pgt0.05 PNS)
  • Does not protect against Type I or Type II errors
  • Non-significant P-value Negative Trial

Absence of evidence is NOT evidence of absence
46
The confidence interval
  • More useful than P-value in evaluating results
  • Provides a range of possible values for the
    true treatment value
  • Width of a CI is a function of sample size
  • Can be calculated for means, medians,
    proportions, odds ratios, relative risks, NNT.
  • 95 most commonly calculated
  • Can go to http//www.openepi.com to help you
    calculate confidence intervals for treatment
    measures

47
Same example
New Antiplatelet for Patients with Acute
Myocardial Infarction Conclusion The new
antiplatelet medication (MiHaart) for acute
myocardial infarction is more effective than
placebo with a 25 reduction in mortality after
60 days of treatment.
ARR 95 CI NNT 95 CI
Composite 6.25 2.6 to 9.9 16 (benefit) 10 to 38.5
High risk patients 5 1.7 to 8.3 20 (benefit) 12 to 59
Low risk patients 1.25 -0.5 to 3.0 80 33 (benefit) to ? and 200 to ? (harm)
48
Confidence intervals andtrials that appear
negative
  • Swedish Cooperative Stroke Study (N505)
  • Aspirin 9 nonfatal stroke
  • Placebo 7 nonfatal stroke
  • Risk difference -2
  • 95 CI (-7 to 3)

49
Trials that appear negative
Statistically no difference Clinically ?
Definitely negative
-7 0 3
Placebo
Aspirin
Inadequate sample size
50
Confidence intervals andtrials that appear
positive
  • Enalapril in LV Dysfunction, SOLVD (N1285)
  • Enalapril 47.7 died or worsening HF
  • Placebo 57.3 died or worsening HF
  • Risk difference 9.6 (10)
  • 95 CI (6 to 14)

51
Trials that appear positive
Statistically there is a difference Clinically ?
inadequate sample size
Definitely relevant
52
  1. Is this relevant?
  2. Is this valid?
  3. Is this reliable?
  4. Is this important and meaningful?
  5. Is this applicable or generalizable?

53
4. Making sense of it allIs this important and
meaningful?
  • Do the results make sense?
  • Do the results provide anything new?
  • Do the results confirm a prior conclusion?
  • Will this change my practice?
  • Do the concluding remarks match the results?

54
5. Is this applicable or generalizable?
  • EXTERNAL validity term phasing out
  • New terms APPLICABILITY or GENERALIZABILITY
  • Was enough information regarding population
    (eligibility criteria), interventions, outcomes,
    study design, and setting reported such that I
    can apply the results to my patients or
    generalize the findings to a broader population?

55
5. Is this applicable or generalizable?
  • Population
  • Recruitment methods?
  • Disease severity or duration of illness?
  • Run-in periods?
  • Interventions
  • Study medication naïve?
  • Dose, duration, other allowed interventions,
    adherence?
  • Level of training for those who assessed
    intervention?
  • Outcomes
  • Long term health outcomes relevant to patients?
  • Intermediate (or surrogate) markers used?
  • Setting
  • Specialty setting or general setting (in-or
    outpatient)?
  • Country?

56
Summary
  • Is this relevant?
  • Is this valid?
  • Is this reliable?
  • Is this important and significant?
  • Is this applicable or generalizable?
  • Developing critical appraisal skill set is
    important for providing quality care
  • Brings awareness of current medical practices and
    highlights areas where more research is needed

57
Acknowledgements
  • Attorney General Consumer and Prescriber
    Education Program
  • Members of the technical advisory committee of
    this grant
  • Office for Oregon Health Policy and Research
  • The University of Texas Southwestern Medical
    Center
  • The Federation of State Medical Boards Research
    and Education Foundation

58
CME instructions
  • Please complete the survey, CME questions, and
    program evaluation after this slide
  • Dont forget to click the finish button at the
    end of the CME questions
  • You should be directly linked to a CME form which
    you will need to fill out and fax, email, or mail
    in order to receive credit hours

59
RCT
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