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Evidence-based medicine process

Evidence-based medicine process. Yodying Punjasawadwong MD., M.Med.Sc, FRCAT Department of Anesthesiology Chiang Mai University Faculty of Medicine , Chiang Mai University 17 November, 2011. Contents:. Definition of evidence-based medicine Steps in evidence based practice

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Evidence-based medicine process

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  1. Evidence-based medicine process Yodying Punjasawadwong MD., M.Med.Sc, FRCAT Department of Anesthesiology Chiang Mai University Faculty of Medicine , Chiang Mai University 17 November, 2011

  2. 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

  3. 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 bestavailable research evidence with clinical expertise, patient values, and circumstance” ( Gordon Guyatt 1992 )

  4. Four steps in evidence-based practice • Formulation a clear clinical question • Search the literature for relevant articles • Critically appraise the evidence for its validity and usefuleness • Implement useful finding in clinical practice

  5. How to practice EBM (the 6 As) Assess patient • History, physical exam and investigation • Clinical expertise Ask clinical question • Recognize the knowledge gaps • Use the PICO structure to form a question Acquire the evidence(s) • Search recent literature • Search EBM resources or societies guidelines Appraise The evidence(s) • Use provided worksheets • Use available software (catnipper) Apply the best evidence • Rank the level of evidences and apply the best • Integrate this with patient values and clinical expertise Assess your performance • In the frequency of performing the whole process • In the efficiency of performing each step

  6. Asking answerable clinical questions:

  7. Why structure questions ? • Ensures efficient search strategy • Requires you to consider the patient populations .. From which evidence can be generalized to your patient • Defines your options for intervention (exposure/study factor) vs. comparator • Defines the important outcomes ( to you; your patient; society) • Defines the most valid study design

  8. What questions do we answer? : Most urgent : Most interesting : Most feasible to answer :Most likely to recur : Most examinable

  9. Two types of clinical questions • Background • Foreground

  10. 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

  11. Rx Dx Px Pathology Physiology Anatomy Foreground Qs-Med Js.“Dated” information Background Q- textbooks Not “dated” student intern resident consultant Experience

  12. Anatomy of question P = Population (Among) I = Intervention (Does) C = Comparison (vs.) O = Outcome (Affect) M = Method (optimal study design)

  13. Clinical Issues and Questions in the Practice of Medicine Diagnosis Prevalence Incidence Risk Prognosis Treatment Prevention Cause

  14. Matching the strongest design to clinical questions Diagnosis Cross-sectional Prevalence Incidence Risk Prognosis Treatment Prevention Cause

  15. Matching the strongest design to clinical questions Diagnosis Cross-sectional Prevalence Cross-sectional Incidence Risk Prognosis Treatment Prevention Cause

  16. Matching the strongest design to clinical questions Diagnosis Cross-sectional Prevalence Cross-sectional Incidence Cohort Risk Prognosis Treatment Prevention Cause

  17. Matching the strongest design to clinical questions Diagnosis Cross-sectional Prevalence Cross-sectional Incidence Cohort Risk Cohort, Case-control Prognosis Cohort Treatment Prevention Cause

  18. Matching the strongest design to clinical questions Diagnosis Cross-sectional Prevalence Cross-sectional Incidence Cohort Risk Cohort, Case-control Prognosis Cohort Treatment RCT Prevention RCT Cause

  19. Matching the strongest design to clinical questions Diagnosis Cross-sectional Prevalence Cross-sectional Incidence Cohort Risk Cohort, Case-control Prognosis Cohort Treatment RCT Prevention RCT Cause Cohort, Case-control

  20. 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 ?

  21. Framing the question Population ‘ air travel/ traveler” Intervention ‘ compression stockings’ Comparison ‘ not use compression stockings” Outcome ‘ deep vein thrombosis

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

  23. A clinical question ‘map’ Why ? : Suggests best study design : Assists plan search strategies

  24. A clinical question ‘map’ Question Study type Data base Best one-line search term ------------- ------------ ------------- -------------------------------- Diagnosis cross sectional, analyticMedline sensitivity. tw Etiology cohort, case-controlMedline risk. tw Prognosis cohort Medline Exp cohort studies/ Intervention RCTs Medline clinical trial.pt Systematic reviewCochrane Meta analysis.pt or Library

  25. Question and search Among air travelers (P) Do compression stockings (I) Affect ( the rate of ) DVTs (O) ? Study type: RCTs Searching - Medline

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

  27. Searching result • Deep vein thrombosis and airtrvel-the deadly duo. AORN J 2003 Feb; 77(2):346-54 • Air travel and venous thrombosis Tidsskr Nor Laegeforen. 2002 Jan:122(16):1579-81. Norwegian • Thromboembolism in travelers Orv Hetil 2001 Nov 11; 142 (45): 2469-73. Review Hungarian • Venous air thrombo-embolism from air travel the LONGFLIT study. Angiology. 2001 June;52(6):369-74 • 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

  28. Selecting articles • Deep vein thrombosis and airtrvel-the deadly duo. AORN J 2003 Feb; 77(2):346-54 • Air travel and venous thrombosis Tidsskr Nor Laegeforen. 2002 Jan:122(16):1579-81. Norwegian • Thromboembolism in travelers Orv Hetil 2001 Nov 11; 142 (45): 2469-73. Review Hungarian • Venous air thrombo-embolism from air travel the LONGFLIT study. Angiology. 2001 June;52(6):369-74 • 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

  29. Basic Steps for Acquiring the Evidence to Support a Clinical Decision Clinical problem Select second most likely resource Define important, searchable question Design search strtegy Design search strategy Poor Select relevant studies Critical appraisal Critical appraisal Apply the evidence Apply the evidence Sackets DL et al. 1998

  30. 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 )

  31. 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

  32. 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

  33. 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

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