1 Introduction to Critical Appraisal Yulia Lin, MD, FRCPC Transfusion Medicine Specialist, Dept of...

11

Introduction to Introduction to Critical AppraisalCritical Appraisal

Yulia Lin, MD, FRCPCYulia Lin, MD, FRCPC

Transfusion Medicine Specialist, Dept of Clinical PathologyTransfusion Medicine Specialist, Dept of Clinical Pathology

Sunnybrook Health Sciences CentreSunnybrook Health Sciences Centre

University of TorontoUniversity of Toronto

TMR Journal Club, September 4, 2008TMR Journal Club, September 4, 2008

22

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

33

Vast amount of literatureVast amount of literature

44

New Studies inTransfusion

55


Past Studies in Transfusion

66


Past Studies in TransfusionStudies in other Sub-specialties

77

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

88

Medical ExpertMedical Expert• Apply principles to evaluate quality of research Apply principles to evaluate quality of research

publicationspublications ScholarScholar

• Critically appraise sources of medical informationCritically appraise sources of medical information• Understand the concepts of clinical research design Understand the concepts of clinical research design • Demonstrate knowledge of basic statistics and Demonstrate knowledge of basic statistics and

epidemiologyepidemiology

99

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

1010

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

1111

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

1212

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…

1313

Type of articlesType of articles

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

DiagnosisDiagnosis PrognosisPrognosis

1414

First, a review…First, a review…

1515

Randomized Controlled TrialRandomized Controlled Trial

Populationselection

Randomization

Intervention A

Intervention B

Outcomesmeasured

1616

Randomized Controlled TrialRandomized Controlled Trial

Population Randomization

Intervention A

Intervention B

Outcomesmeasured

Is aprotinin superior to lysine analogs in high-risk cardiac surgery?

Fergusson DA et al. NEJM May 29, 2008.

1717

Observational Case-ControlObservational Case-Control

Population

Cases(+Disease)

Control(No disease)

Exposure to Risk Factor

Exposed

Yes

No

Yes

No

1818


Population

Cases(+Disease)

Control(No disease)


Exposed

Yes

No

Yes

No

Retrospective

1919


Population

Cases(+Disease)

Control(No disease)


Exposed

Yes

No

Yes

No

Blood transfusion, anesthesia, surgery and risk of NHLin a population-based case-control study.Cerhan JR et al. Int J Cancer 2008 Aug 15.

2020

Observational CohortObservational Cohort

Cohort

Cohort without Disease


Population

Exposed

Not exposed

Disease

Yes

No

Yes

No

2121

Cohort StudiesCohort StudiesPast Present Future

Follow-upCohort assembled

RetrospectiveCohort Study

2222




The ratio of fibrinogen to red cells transfused affects survival incasualties receiving massive transfusions

at an army combat support hospital.Stinger HK et al., J Trauma February 2008;64:S79-85.

Red blood cell to plasma ratios transfused during massive transfusion are associated with mortality in severe multiplyInjury: a retrospective analysis from Deutsche Gesellschaft.

Maegele M et al. Vox Sang August 2008;95:112-119.

2323





ProspectiveCohort Study

2424





ProspectiveCohort Study

Prospective evaluation of a transfusion policy of D+ red blood cells into D- patients.

Gonzalez-Porras JR et al. Transfusion July 2008.

2525

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

2626

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

Comparing the efficacy and safety of apheresis and whole-blood derived platelet transfusions: a systematic review.

Heddle NM et al. Transfusion July 2008.

2727

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

2828

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 for policies on alternatives to allogeneic blood transfusion:1. Predeposit autologous blood donation and transfusionBoulton FE et al. Transfusion Medicine 2007;17:354-65

2929

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

3030

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) but also ed) but also

on-line at on-line at http://ugi.usersguides.org/usersguides/hg/hh_sthttp://ugi.usersguides.org/usersguides/hg/hh_start.aspart.asp

• Centre for Health Evidence Website: Centre for Health Evidence Website: http://www.cche.net/usersguides/main.asphttp://www.cche.net/usersguides/main.asp

For guidelines, different instrumentsFor guidelines, different instruments• AGREE instrument: AGREE instrument:

http://www.agreetrust.org/instrument.htmhttp://www.agreetrust.org/instrument.htm• GRADE instrument available at Blood DepotGRADE instrument available at Blood Depot

http://ugi.usersguides.org/usersguides/hg/hh_start.asp

http://ugi.usersguides.org/usersguides/hg/hh_start.asp

http://www.cche.net/usersguides/main.asp

http://www.agreetrust.org/instrument.htm

3434

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?

3535

RCTRCT


Intervention A

Intervention B

Outcomesmeasured

3636

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


Intervention A

Intervention B

Outcomesmeasured

Did experimental & control groups begin the study with a similar prognosis? Were patients randomized? Was randomization concealed? Were patients analyzed in the groups to which they were randomized? Were groups similar with respect to known prognostic variables?

3737

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


Intervention A

Intervention B

Outcomesmeasured

Did experimental & control groups retain a similar prognosis after the study started? Were patients, clinicians, outcome assessors blinded? Was follow-up complete?

3838

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?

3939

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

Were the study patients similar to the patient in my practice?

4040

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

Were the study patients similar to the patient in my practice?Were all clinically important outcomes considered?Are the likely treatment benefits worth the potential harm and costs?

4141

Observational CohortObservational Cohort

Cohort



Population

Exposed

Not exposed

Disease

Yes

No

Yes

No

4242

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

Cohort



Population

Exposed

Not exposed

Disease

Yes

No

Yes

No

Did expt and control groups begin the study with a similar prognosis? Did the investigators demonstrate similarity in all known determinants of outcome? Did they adjust for differences in the analysis?

4343

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

Cohort



Population

Exposed

Not exposed

Disease

Yes

No

Yes

No

Did expt and control groups retain a similar prognosis after the study started? Were the outcomes measured in the same way in the groups being compared? Was follow-up sufficiently complete?

4444

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

Cohort



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?

4545

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

Cohort



Population

Exposed

Not exposed

Disease

Yes

No

Yes

No

Were the study patients similar to my patients?

4646

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

Cohort



Population

Exposed

Not exposed

Disease

Yes

No

Yes

No

Were the study patients similar to my patients?Was the duration of follow-up adequate?Was was the magnitude of the risk?Should I attempt to stop the exposure?

4747

Putting it all together…Putting it all together…

4848

Tips for TMR Journal ClubTips for TMR Journal Club

Choose the article carefully Choose the article carefully 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 Try explaining a new concept (bias, Try explaining a new concept (bias,

statistical concept)statistical concept)• External validity: Take a standExternal validity: Take a stand

Allow ½ the time for discussionAllow ½ the time for discussion

1 Introduction to Critical Appraisal Yulia Lin, MD, FRCPC Transfusion Medicine Specialist, Dept of...

Documents

Transcript of 1 Introduction to Critical Appraisal Yulia Lin, MD, FRCPC Transfusion Medicine Specialist, Dept of...