Download - Evidence-based medicine process
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