1 introduction to critical appraisal yulia lin, md, frcpc transfusion medicine & hematology...

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

Why is Critical Appraisal Why is Critical Appraisal important?important?

Vast amount of literatureVast amount of literature

New Studies inTransfusion

Past Studies in Transfusion

New Studies inTransfusion

Past Studies in TransfusionStudies in other Sub-specialties

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

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

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

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

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

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…

Type of articlesType of articles

Randomized controlled trials – TherapyRandomized controlled trials – Therapy Observational studies – HarmObservational studies – Harm Systematic ReviewsSystematic Reviews GuidelinesGuidelines

DiagnosisDiagnosis PrognosisPrognosis

First, a review…First, a review…

Randomized Controlled TrialRandomized Controlled Trial

Population Randomization

Intervention A

Intervention B

Outcomesmeasured

Intervention A

Intervention B

Outcomesmeasured

Which article?

Randomization

Fill in the blanks above:Population? Intervention? Outcome?

Intervention A

Intervention B

Outcomesmeasured

Which article?

Randomization

Fill in the blanks above:Population? Intervention? Outcome?

Observational Case-ControlObservational Case-Control

Population

Cases(+Disease)

Control(No disease)

Exposure to Risk Factor

Exposed

Population

Cases(+Disease)

Control(No disease)

Exposed

Retrospective

Population

Cases(+Disease)

Control(No disease)

Exposed

Which article?

Cases?

Controls?

Risk factor?

Exposed

Fill in the blanks:Population? Who are the cases and controls?

What are the risk factors?

Observational CohortObservational Cohort

Cohort

Cohort without Disease

Population

Exposed

Not exposed

Disease

Cohort StudiesCohort StudiesPast Present Future

Follow-upCohort assembled

RetrospectiveCohort Study

Which article?

Fill in the blanks:Who is the cohort? What is the risk factor? What is the outcome?

ProspectiveCohort Study

Which article?

Fill in the blanks above:Who is the cohort? What is the risk factor? What is the outcome?

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

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

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

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

How to do a critical appraisal?How to do a critical appraisal?

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/

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?

RCTRCT

Intervention A

Intervention B

Outcomesmeasured

RCT - Are the results valid?RCT - Are the results valid?

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?

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

RCT - What were the results?RCT - What were the results?

Intervention A

Intervention B

Outcomesmeasured

How large was the treatment effect?How precise was the estimate of the treatment effect?

RCT - What were the results?RCT - What were the results?

Intervention A

Intervention B

Outcomesmeasured

How large was the treatment effect?How precise was the estimate of the treatment effect?

RCT - How can I apply the RCT - How can I apply the results to patient care?results to patient care?

Intervention A

Intervention B

Outcomesmeasured

Can the results be applied to my patients?

RCT - How can I apply the RCT - How can I apply the results to patient care?results to patient care?

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?

Observational CohortObservational Cohort

Cohort

Population

Exposed

Not exposed

Disease

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

Cohort - Are the results valid?Cohort - Are the results valid?

Pts receivinghigh plasma

volume donations

from LAPS II

All hospitalpatients

HLA ab pos

HLA ab neg

Disease

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?

Cohort - Are the results valid?Cohort - Are the results valid?

Pts receivinghigh plasma

volume donations

from LAPS II

All hospitalpatients

HLA ab pos

HLA ab neg

Disease

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?

Cohort - What are the results?Cohort - What are the results?

Cohort

Population

Exposed

Not exposed

Disease

How strong is the association between exposure and outcome? Consider magnitude and dose response?How precise is the estimate of the risk?

Cohort - What are the results?Cohort - What are the results?

Cohort

Population

Exposed

Not exposed

Disease

How strong is the association between exposure and outcome? Consider magnitude and dose response?How precise is the estimate of the risk?

Cohort - How can I apply the results?Cohort - How can I apply the results?

Cohort

Population

Exposed

Not exposed

Disease

Are the results applicable to my patients?

Cohort - How can I apply the results?Cohort - How can I apply the results?

Cohort

Population

Exposed

Not exposed

Disease

Are the results applicable to my patients?What is the magnitude of the risk?Should I attempt to stop the exposure?

Putting it all together…Putting it all together…

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

1 introduction to critical appraisal yulia lin, md, frcpc transfusion medicine & hematology...

transfusion slide

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review slide

medical literature slide

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jama transfusion

articleany article

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