Evidence-based medicine process

Yodying Punjasawadwong MD., M.Med.Sc, FRCATDepartment of Anesthesiology

Chiang Mai University

Faculty of Medicine , Chiang Mai University17 November, 2011

Contents: Definition of evidence-based medicine Steps in evidence based practice Asking answerable clinical questions Matching research designs to clinical questions A clinical question map for searching ( example ) Example Level of evidence and recommendation

Definition

“Evidence Based Medicine is the conscientious, explicit and judicious use of current best evidence in making decision about the care of individual patients.

“ Evidence Based Practice of Medicine is the integration of the best available research evidence with clinical expertise, patient values, and circumstance”

( Gordon Guyatt 1992 )

Four steps in evidence-based practice

1. Formulation a clear clinical question2. Search the literature for relevant articles3. Critically appraise the evidence for its

validity and usefuleness4. Implement useful finding in clinical

practice

AAssessssesspatientpatient

AAskskclinical questionclinical question

AAcquirecquirethe evidence(s)the evidence(s)

AAppraiseppraiseThe evidence(s)The evidence(s)

AApplypplythe best evidencethe best evidence

AAssessssessyour performanceyour performance

How to practice EBM (the 6 How to practice EBM (the 6 AAs)s)

• Recognize the knowledge gapsRecognize the knowledge gaps

• Use the PICO structure to form a questionUse the PICO structure to form a question

• Search recent literatureSearch recent literature

• Search EBM resources or societies guidelinesSearch EBM resources or societies guidelines

• Use provided worksheetsUse provided worksheets

• Use available software (catnipper)Use available software (catnipper)

• Rank the level of evidences and apply the bestRank the level of evidences and apply the best

• Integrate this with patient values and clinical expertiseIntegrate this with patient values and clinical expertise

• In the frequency of performing the whole processIn the frequency of performing the whole process

• In the efficiency of performing each stepIn the efficiency of performing each step

• History, physical exam and investigationHistory, physical exam and investigation

• Clinical expertiseClinical expertise

Asking answerable clinical questions:

Why structure questions ?1. Ensures efficient search strategy2. Requires you to consider the patient

populations .. From which evidence can be generalized to your patient

3. Defines your options for intervention (exposure/study factor) vs. comparator4. Defines the important outcomes ( to you;

your patient; society)5. Defines the most valid study design

What questions do we answer?

: Most urgent: Most interesting: Most feasible to answer:Most likely to recur: Most examinable

Two types of clinical questions• Background

• Foreground

Two types of clinical questions Background Foreground ---------------------- ------------------------Elements 2-part 4(or3) part,PICO

Focus general specific

Asked by learners clinicians/patients

Example What is… What is wrong with me? How dose.. Why am I sick ?

What is going to happen? How should I be treated ?Answer stable..from up to date..from text book research data

Background Q- textbooks

Not “dated”

Foreground Qs-Med Js.“Dated” information

student intern resident consultant

Experience

Rx

Dx

Px

Pathology

Physiology

Anatomy

Anatomy of question

P = Population (Among)I = Intervention (Does)C = Comparison (vs.)O = Outcome (Affect)

M = Method (optimal study design)

Clinical Issues and Questions in the Practice of Medicine

DiagnosisPrevalenceIncidenceRiskPrognosisTreatmentPreventionCause

Matching the strongest design to clinical questionsDiagnosis Cross-sectionalPrevalenceIncidence RiskPrognosisTreatmentPreventionCause

Matching the strongest design to clinical questionsDiagnosis Cross-sectionalPrevalence Cross-sectionalIncidence RiskPrognosisTreatmentPreventionCause

Matching the strongest design to clinical questionsDiagnosis Cross-sectionalPrevalence Cross-sectionalIncidence CohortRiskPrognosisTreatmentPreventionCause

Matching the strongest design to clinical questionsDiagnosis Cross-sectionalPrevalence Cross-sectionalIncidence CohortRisk Cohort, Case-controlPrognosis CohortTreatment PreventionCause

Matching the strongest design to clinical questionsDiagnosis Cross-sectionalPrevalence Cross-sectionalIncidence CohortRisk Cohort, Case-controlPrognosis CohortTreatment RCTPrevention RCTCause

Matching the strongest design to clinical questionsDiagnosis Cross-sectionalPrevalence Cross-sectionalIncidence CohortRisk Cohort, Case-controlPrognosis CohortTreatment RCTPrevention RCTCause Cohort, Case-control

Trish’s scenario Trish, a secretary, is planning a quick

trip to & from the U.K ( ‘ long haul’) to visit her sick aunt

- Trish is aged 59 yrs, post-menopausal, taking HRT & is overweight.

- She has read in newspaper: compression stockings stop DVTs’

- Trish asks you; “ Should I wear compression stockings on the plane ?

Framing the questionPopulation ‘ air travel/ traveler”

Intervention ‘ compression stockings’

Comparison ‘ not use compression stockings”

Outcome ‘ deep vein thrombosis

Asking Question:Among air travelers (P)Do compression stockings (I)Compared with not using (C)Affect ( the rate of ) DVTs (O) ?

A clinical question ‘map’

Why ?: Suggests best study design

: Assists plan search strategies

A clinical question ‘map’Question Study type Data base Best

one-line search term------------- ------------ -------------

--------------------------------Diagnosis cross sectional, analytic Medline

sensitivity. tw

Etiology cohort, case-control Medline risk. tw

Prognosis cohort Medline Exp cohort studies/

Intervention RCTs Medline clinical trial.pt

Systematic review Cochrane Meta analysis.pt or

Library

Question and searchAmong air travelers (P)Do compression stockings (I)Affect ( the rate of ) DVTs (O) ?Study type: RCTsSearching - Medline

Med line : Search for RCT

“ PubMed” Use searching terms based on PICO (Other interfaces: apply ‘ limited’ Publication Type- RCT..if excessive)

Searching result1. Deep vein thrombosis and airtrvel-the deadly duo. AORN J 2003 Feb; 77(2):346-54

2. Air travel and venous thrombosis Tidsskr Nor Laegeforen. 2002 Jan:122(16):1579-81. Norwegian

2. Thromboembolism in travelers Orv Hetil 2001 Nov 11; 142 (45): 2469-73. Review Hungarian

4. Venous air thrombo-embolism from air travel the LONGFLIT study. Angiology. 2001 June;52(6):369-74

5. Frequency and prevention of symptomless deep-vein thrombosis in long haul flight: a randomized trial. Lancet 2001 May 12; 357(9267):1485-

6. Economy class syndrome Aviates Space Environ Med 1994 Oct; 65(10 part 1):957-60

Selecting articles1. Deep vein thrombosis and airtrvel-the deadly duo. AORN J 2003 Feb; 77(2):346-

54

2. Air travel and venous thrombosis Tidsskr Nor Laegeforen. 2002 Jan:122(16):1579-81. Norwegian

2. Thromboembolism in travelers Orv Hetil 2001 Nov 11; 142 (45): 2469-73. Review Hungarian

4. Venous air thrombo-embolism from air travel the LONGFLIT study. Angiology. 2001 June;52(6):369-74

5. Frequency and prevention of symptomless deep-vein thrombosis in long haul flight: a randomized trial. Lancet 2001 May 12; 357(9267):1485-9

6. Economy class syndrome Aviates Space Environ Med 1994 Oct; 65(10 part 1):957-60

Clinical problem

Define important, searchable questionDesign search strtegySelect relevant studiesCritical appraisalApply the evidence

Select second

most likely resourceDesign search

strategyCritical appraisal

Apply the evidence

Poor

Basic Steps for Acquiring the Evidence to Support a Clinical Decision

Sackets DL et al. 1998

Categories of evidence I

I : Experimental study design/randomized controlled trial(RCT)

II: Quasi experimental study design/ non-randomized controlled study design

III:Non-experimental study design such as cohort studies, correlation studies and case-control studies

IV: Evidence from expert committee reports or opinions/and/or clinical experience of respect authorities

( adaped from AHCPR 1992 )

Categories of evidence I Ia : evidence from systematic review/meta-analysis of RCT Ib: evidence from at least one RCT IIa: evidence from at least one controlled study without

randomization IIb:evidence from at least one other type of quasi-experimental

studies III:evidence from non-experimental studies, such as comparative

studies, correlation studies and case-control studies IV:evidence from expert committee reports or opinions/ and /or

clinical experience of respect authorities

Strength of recommendation

A directly based on category I evidence B directly based on category II evidence or

extrapolated recommendation from category I evidence C directly based on category III evidence or

extrapolated recommendation from category I or II evidence

D directly basd on category IV evidence or extrapolated recommendation from category I,II or III evidence

Factors contributing to the process of deriving recommendations

The nature of evidence ( e.g. its susceptibility to bias)

The applicability of the evidence to the population of interest(its generaliaability)

Resource implications and their cost Knowledge of the health care system Beliefs and value of the panel