1 introduction to critical appraisal yulia lin, md, frcpc transfusion medicine & hematology...
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Introduction to Introduction to Critical AppraisalCritical Appraisal
Yulia Lin, MD, FRCPCYulia Lin, MD, FRCPC
Transfusion Medicine & Hematology Transfusion Medicine & Hematology
Sunnybrook Health Sciences CentreSunnybrook Health Sciences Centre
University of TorontoUniversity of Toronto
TMR Journal Club, September 6, 2011TMR Journal Club, September 6, 2011
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Why is Critical Appraisal Why is Critical Appraisal important?important?
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Vast amount of literatureVast amount of literature
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New Studies inTransfusion
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New Studies inTransfusion
Past Studies in Transfusion
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New Studies inTransfusion
Past Studies in TransfusionStudies in other Sub-specialties
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Why critical appraisal is important?Why critical appraisal is important?
Impossible to keep up with all of the Impossible to keep up with all of the literatureliterature
Enables us to distinguish stronger Enables us to distinguish stronger evidence from weaker evidenceevidence from weaker evidence
Allows us to appropriately incorporate the Allows us to appropriately incorporate the evidence into our practice so as to evidence into our practice so as to improve patient careimprove patient care
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Transfusion Medicine Residency ObjectivesTransfusion Medicine Residency Objectives ScholarScholar 2 - Evaluate medical information and its sources 2 - Evaluate medical information and its sources
critically, and apply this appropriately to practice critically, and apply this appropriately to practice decisionsdecisions• Describe the principles of critical appraisalDescribe the principles of critical appraisal• Critically appraise retrieved evidence in order to address Critically appraise retrieved evidence in order to address
a clinical questiona clinical question• Integrate critical appraisal conclusions into clinical careIntegrate critical appraisal conclusions into clinical care• Critically review published literature and apply Critically review published literature and apply
appropriate utilization principles/practices /guidelinesappropriate utilization principles/practices /guidelines
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Purpose of TMR Journal ClubPurpose of TMR Journal Club
1.1. To present a recent article in the To present a recent article in the transfusion literaturetransfusion literature
2.2. To learn how to critically appraise the To learn how to critically appraise the medical literature medical literature
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Steps to a successful JCSteps to a successful JC
1.1. Choosing the articleChoosing the article
2.2. Presenting the articlePresenting the article
3.3. Critically appraising the articleCritically appraising the article
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Choosing an article…Choosing an article…
Where to find an article?Where to find an article?• Recent table of contents Recent table of contents
NEJM, Lancet, JAMANEJM, Lancet, JAMA Transfusion, Vox Sanguinis, Blood, etc.Transfusion, Vox Sanguinis, Blood, etc.
• Transfusion Medicine Reviews – Journal ClubTransfusion Medicine Reviews – Journal Club• Transfusion Medicine CommunityTransfusion Medicine Community• List of interesting articlesList of interesting articles
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Choosing the article…Choosing the article…
Which article?Which article?• RelevantRelevant• Interesting to youInteresting to you
What type of article?What type of article?• Any articleAny article• But some are easier than others…But some are easier than others…
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Type of articlesType of articles
Randomized controlled trials – TherapyRandomized controlled trials – Therapy Observational studies – HarmObservational studies – Harm Systematic ReviewsSystematic Reviews GuidelinesGuidelines
DiagnosisDiagnosis PrognosisPrognosis
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First, a review…First, a review…
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Randomized Controlled TrialRandomized Controlled Trial
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
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Randomized Controlled TrialRandomized Controlled Trial
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
Which article?
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Randomized Controlled TrialRandomized Controlled Trial
Randomization
Fill in the blanks above:Population? Intervention? Outcome?
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Randomized Controlled TrialRandomized Controlled Trial
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
Which article?
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Randomized Controlled TrialRandomized Controlled Trial
Randomization
Fill in the blanks above:Population? Intervention? Outcome?
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Observational Case-ControlObservational Case-Control
Population
Cases(+Disease)
Control(No disease)
Exposure to Risk Factor
Exposed
Yes
No
Yes
No
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Observational Case-ControlObservational Case-Control
Population
Cases(+Disease)
Control(No disease)
Exposure to Risk Factor
Exposed
Yes
No
Yes
No
Retrospective
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Observational Case-ControlObservational Case-Control
Population
Cases(+Disease)
Control(No disease)
Exposure to Risk Factor
Exposed
Yes
No
Yes
No
Which article?
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Observational Case-ControlObservational Case-Control
Cases?
Controls?
Risk factor?
Exposed
Yes
No
Yes
No
Fill in the blanks:Population? Who are the cases and controls?
What are the risk factors?
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Observational CohortObservational Cohort
Cohort
Cohort without Disease
Exposure to Risk Factor
Population
Exposed
Not exposed
Disease
Yes
No
Yes
No
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Cohort StudiesCohort StudiesPast Present Future
Follow-upCohort assembled
RetrospectiveCohort Study
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Cohort StudiesCohort StudiesPast Present Future
Follow-upCohort assembled
RetrospectiveCohort Study
Which article?
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Cohort StudiesCohort StudiesPast Present Future
Fill in the blanks:Who is the cohort? What is the risk factor? What is the outcome?
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Cohort StudiesCohort StudiesPast Present Future
Follow-upCohort assembled
RetrospectiveCohort Study
Follow-upCohort assembled
ProspectiveCohort Study
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Cohort StudiesCohort StudiesPast Present Future
Follow-upCohort assembled
RetrospectiveCohort Study
Follow-upCohort assembled
ProspectiveCohort Study
Which article?
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Cohort StudiesCohort StudiesPast Present Future
Follow-upCohort assembled
RetrospectiveCohort Study
Fill in the blanks above:Who is the cohort? What is the risk factor? What is the outcome?
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Systematic ReviewSystematic Review
OverviewOverview• Summary of the medical literature that Summary of the medical literature that
attempts to address a focused clinical questionattempts to address a focused clinical question Systematic reviewSystematic review
• Using methods designed to reduce the Using methods designed to reduce the likelihood of biaslikelihood of bias
Meta-analysisMeta-analysis• Review that uses quantitative methods to Review that uses quantitative methods to
summarize the resultssummarize the results
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Systematic ReviewSystematic Review
Systematic reviewSystematic review• Using methods designed to reduce the Using methods designed to reduce the
likelihood of biaslikelihood of bias Meta-analysisMeta-analysis
• Review that uses quantitative methods to Review that uses quantitative methods to summarize the resultssummarize the results
Meta-analysis of the randomized controlled trials of the hemostatic efficacy and capacity of pathogen-reduced platelets.
Vamvakas EC. Transfusion May 2011;51:1058-71
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GuidelinesGuidelines
““Systematically developed statements to Systematically developed statements to assist practitioner and patient decisions assist practitioner and patient decisions about appropriate health care for specific about appropriate health care for specific clinical circumstances”clinical circumstances”• Attempt to address all issues and values relevant Attempt to address all issues and values relevant
to a clinical decisionto a clinical decision• Attempt to distill a large body of medical Attempt to distill a large body of medical
expertise into a convenient, readily usable formatexpertise into a convenient, readily usable format• Make explicit recommendations with definite Make explicit recommendations with definite
intent to influence what clinicians dointent to influence what clinicians do
Field MJ. Clinical practice guidelines. 1990Hayward et al. JAMA 1995;274:570-4
Cook et al. Ann Int Med 1997;127:210-6
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GuidelinesGuidelines
““Systematically developed statements to Systematically developed statements to assist practitioner and patient decisions assist practitioner and patient decisions about appropriate health care for specific about appropriate health care for specific clinical circumstances”clinical circumstances”
Guidelines on oral anticoagulation with warfarin, 4th edition. BCSH 2010.
http://www.bcshguidelines.com/documents/warfarin_4th_ed.pdf
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How to do a critical appraisal?How to do a critical appraisal?
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Critical appraisal methodsCritical appraisal methods
Most are based on Users’ Guides to the Most are based on Users’ Guides to the Medical Literature Medical Literature • Available in a textbook form (2Available in a textbook form (2ndnd ed) ed) • Brief version Brief version http://
www.ebem.org/usersguide.html For guidelines, different instrumentsFor guidelines, different instruments
• AGREE instrument: AGREE instrument: http://www.agreetrust.org/resource-centre/agree-ii/
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Steps to Critical AppraisalSteps to Critical Appraisal
1.1. Are the results valid?Are the results valid?• Have the results been influenced in a Have the results been influenced in a
systematic fashion so as to lead to a false systematic fashion so as to lead to a false conclusion?conclusion?
2.2. What are the results?What are the results?
3.3. How can I apply the results to patient How can I apply the results to patient care? care?
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RCTRCT
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
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RCT - Are the results valid?RCT - Are the results valid?
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
Was the assignment of patients to treatment randomized?Were all patients who entered the trial accounted for and attributed at its conclusion?Were patients, clinicians and study personnel kept "blind" to treatment received?Were the groups similar at the start of the trial?Aside from the experimental intervention were the groups treated equally?
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RCT - Are the results valid?RCT - Are the results valid?
Randomization
Adherence totransfusion strategies
Was the assignment of patients to treatment randomized?Were all patients who entered the trial accounted for and attributed at its conclusion?Were patients, clinicians and study personnel kept "blind" to treatment received?Were the groups similar at the start of the trial?Aside from the experimental intervention were the groups treated equally?
Elective cardiac SurgeryN=50
RestrictiveHb <70 CPBHb <75 postop
LiberalHb <95 CPBHb <100 postop
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RCT - What were the results?RCT - What were the results?
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
How large was the treatment effect?How precise was the estimate of the treatment effect?
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RCT - What were the results?RCT - What were the results?
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
How large was the treatment effect?How precise was the estimate of the treatment effect?
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RCT - How can I apply the RCT - How can I apply the results to patient care?results to patient care?
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
Can the results be applied to my patients?
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RCT - How can I apply the RCT - How can I apply the results to patient care?results to patient care?
Population Randomization
Intervention A
Intervention B
Outcomesmeasured
Can the results be applied to my patients?Were all clinically important outcomes considered?Are the likely treatment benefits worth the potential harm and costs?
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Observational CohortObservational Cohort
Cohort
Cohort without Disease
Exposure to Risk Factor
Population
Exposed
Not exposed
Disease
Yes
No
Yes
No
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Cohort StudiesCohort StudiesPast Present Future
Incidence of TRALIPts receivinghigh plasmavolume donations from LAPS II
LAPS II: a retrospective cohort study of transfusion-relatedacute lung injury in recipients of high-plasma-volume human
Leukocyte antigen antibody-positive or –negative components.Kleinman et al. Transfusion. Published online Mar 29, 2011.
Exposure to HLA ab posvs neg donations
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Cohort - Are the results valid?Cohort - Are the results valid?
Pts receivinghigh plasma
volume donations
from LAPS II
Cohort without Disease
Exposure to Risk Factor
All hospitalpatients
HLA ab pos
HLA ab neg
Disease
TRALI
No
TRALI
No
Except for the exposure under study, were the compared groups similar to each other?Were the outcomes and exposures measured in the same ways in both groups?Was the follow-up of patients sufficiently long and complete?Is the temporal relationship correct?Is there a dose-response gradient?
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Cohort - Are the results valid?Cohort - Are the results valid?
Pts receivinghigh plasma
volume donations
from LAPS II
Cohort without Disease
Exposure to Risk Factor
All hospitalpatients
HLA ab pos
HLA ab neg
Disease
TRALI
No
TRALI
No
Except for the exposure under study, were the compared groups similar to each other?Were the outcomes and exposures measured in the same ways in both groups?Was the follow-up of patients sufficiently long and complete?Is the temporal relationship correct?Is there a dose-response gradient?
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Cohort - What are the results?Cohort - What are the results?
Cohort
Cohort without Disease
Exposure to Risk Factor
Population
Exposed
Not exposed
Disease
Yes
No
Yes
No
How strong is the association between exposure and outcome? Consider magnitude and dose response?How precise is the estimate of the risk?
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Cohort - What are the results?Cohort - What are the results?
Cohort
Cohort without Disease
Exposure to Risk Factor
Population
Exposed
Not exposed
Disease
Yes
No
Yes
No
How strong is the association between exposure and outcome? Consider magnitude and dose response?How precise is the estimate of the risk?
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Cohort - How can I apply the results?Cohort - How can I apply the results?
Cohort
Cohort without Disease
Exposure to Risk Factor
Population
Exposed
Not exposed
Disease
Yes
No
Yes
No
Are the results applicable to my patients?
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Cohort - How can I apply the results?Cohort - How can I apply the results?
Cohort
Cohort without Disease
Exposure to Risk Factor
Population
Exposed
Not exposed
Disease
Yes
No
Yes
No
Are the results applicable to my patients?What is the magnitude of the risk?Should I attempt to stop the exposure?
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Putting it all together…Putting it all together…
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Tips for TMR Journal ClubTips for TMR Journal Club
Choose the article carefully Choose the article carefully Include brief background for contextInclude brief background for context Present the article briefly (10 slides)Present the article briefly (10 slides) The main objective is the critical appraisalThe main objective is the critical appraisal
• Internal validity: Internal validity: Focus on 1-2 key pointsFocus on 1-2 key points Explain one concept (bias, statistical test)Explain one concept (bias, statistical test)
• External validity: Take a standExternal validity: Take a stand Allow 20-30 minutes for discussionAllow 20-30 minutes for discussion