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Making evidence more accessible using pictures Rod Jackson Oxford 8/9/09.

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Presentation on theme: "Making evidence more accessible using pictures Rod Jackson Oxford 8/9/09."— Presentation transcript:

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2 Making evidence more accessible using pictures Rod Jackson Oxford 8/9/09

3 What is Evidence Based Practice?

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5 The 6 steps of Evidence Based Practice 1.ASK a focussed question 2.ACCESS - search for epidemiological evidence to help answer question 3.APPRAISE the evidence for its validity, effect size, precision) 4.AGGREGATE the evidence with patient/community, clinical/hlth & policy issues & make an evidence- based decision 5.APPLY your decision 6.[AUDIT your practice (i.e. check your actual practice against evidence-based practice on a regular basis)].

6 The GATE frame Graphic Approach To Epidemiology ©

7 Participants Exposure GroupComparison Group Outcomes Time P E C O T PECOT: the 5 parts of every epidemiological study All epidemiological studies can be hung on the GATE frame

8 EBP Step 1: ASK - turn your question into 5 parts (PECOT) 1.Participants (patient(s) you want to treat) 2.Exposure (an intervention if about therapy) 3.Comparison (there is always an alternative! - another therapy, nothing … 4.Outcome (usually a disease or condition you want to prevent or manage) 5.Time frame (over which you expect a result)

9 EBP Step 2: ACCESS - search for the best evidence to answer your questions Use the PECOT components to choose search terms

10 P EC O T P E C O T Recruitment Allocation Maintenance Blind or Objective measurements & processes EBP Step 3: Appraise the evidence using PECOT & RAMBO on the GATE frame

11 EBP Step 4: AGGREGATE the relevant information & make an evidence-based decision:’ the X-factor ©

12 Epidemiologic evidence Clinical / population health considerations Policy issues Patient / community preferences X-factor: making evidence-based decisions expertise: ‘putting it all together’ the art of practice

13 Step 5 APPLY Implementation!

14 Step 6: AUDIT - evaluate & improve performance 1. Determine ‘best’ practice (EBP Steps 1-4) 2. Assess current practice: survey 3. Compare with best practice - is there a gap? 4. Consider reasons for gap, identify processes to reduce gap & implement 5. Re-survey: is there any improvement? = quality improvement / audit

15 GATE Graphic Approach To Epidemiology Graphic Appraisal Tool for Epidemiology Graphic Architectural Tool for Epidemiology

16 The GATE frame © the shape of every epidemiological study

17 GATE study design (PECOT) P E C O T

18 GATE study analyses (EGO & CGO) ab cd EG CG

19 GATE study appraisal (RAMBO) P E C O T Recruitment Allocation Maintenance Blind or Objective measurements & processes

20 GATE study design (PECOT) Participants Exposure GroupComparison Group Outcomes Time P E C O T

21 Participants Study Setting Eligible Participants Participants P

22 Exposure & Comparison Groups Exposure or Intervention Group (EG) Comparison or Control Group (CG) EG CG

23 Outcomes (O) O ab cd yes no ‘Dis-ease’

24 Time (T) T incidence prevalence

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26 GATE study analyses

27 Denominator (Participants) D N Numerator (Outcomes) O = N÷D All epidemiological studies involve measuring the OCCURRENCE of disease Occurrence = Numerator ÷ Denominator

28 GATE study analyses P EG CG O Denominator 1: Exposure Group EG Numerator 1: a Denominator 2: Comparison Group CG Overall Denominator ab cd Numerator 2: b

29 Occurrence = N ÷ D P EG CG O Denominator 1: Exposure Group EG Numerator 1: a Denominator 2: Comparison Group CG ab cd Numerator 2: b Exposure Group Occurrence: EGO = a ÷ EG Comparison Group Occurrence: CGO = b ÷ CG

30 Estimating effects & associations involves comparing occurrences Relative Effect or Risk = EGO ÷ CGO e.g. relative risk (RR), risk ratio, prevalence ratio, incidence ratio Absolute Effect or Risk Difference = EGO - CGO e.g. risk difference (RD), absolute risk Number Needed To Treat (NNT) = 1 ÷ RD

31 Analyses it’s all about EGO & CGO

32 Occurrence = N÷D per unit of time P EG CG O Denominator 1: Exposure Group EG x T Numerator 1= a Denominator 2: Comparison Group CG x T ab cd Numerator 2 = b Exposure Group Occurrence: EGO = a ÷ (EG x T) Comparison Group Occurrence: CGO = b ÷ (CG x T) ‘person-time exposure’

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34 GATE study appraisal (RAMBO) P E C O T Recruitment Allocation Maintenance Blind or Objective measurements & processes

35 Study appraisal How well was the study done? Was it ok (  or +) or not ok (  )? or unclear (?) or not applicable (n/a) ‘no study is perfect!’

36 R AMBO E C O T appropriate Recruitment? participants representative of target population P Study setting & eligibility criteria well described? Recruit random sample OR Recruit consecutive eligibles ‘appropriateness’ depends on study question

37 R A MBO EG CG O T appropriate Allocation process? were EG & CG comparable P Allocation process well described? If allocated by investigators: Allocated randomly (e.g drugs) AND Concealed allocation OR If allocated by measurement (e.g. smoking): Adjusted for differences between EG & CG (e.g. statistical or matching) Allocate

38 EG CG O T P RCT: Allocate randomly by investigators (e.g drugs) EG CG O T P Cohort: Allocate by measurement (e.g. smoking)

39 RA M BO EG CG O T good Maintenance? did participants remain in allocated groups (EG & CG) P Participants &/or investigators blind to exposure (and comparison exposure)? Compliance high & similar in EG & CG Contamination low & similar in EG & CG Co-interventions low & similar in EG & CG Completeness of follow-up high & similar in EG & CG

40 RAM BO EG CG O T Blind or Objective? measurements & processes P Allocation concealed (blind) if randomised EG & CG measurements well described Outcome measurements well described Allocation/Measurement process similar for all participants If measurement not objective (eg. automated or definitive) were assessors blind to exposure (and comparison exposure) A

41 The GATE approach: every epidemiological study hangs on the GATE frame There is only one basic study design: Cohort (& case-control) studies - aetiology / prognosis / intervention RCT (a randomised cohort study)- interventions Cross-sectional studies - diagnosis

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43 Cohort (follow-up) study: archetypal epidemiological approach Participants Exposure GroupComparison Group Outcomes Time P E C O T Allocated by measurement (not by randomisation) Best design for investigating aetiology (risk), prognosis

44 Randomised controlled trial - cohort study where exposure allocated by randomisation process Participants Exposure GroupComparison Group Outcomes Time P E C O T Allocated by randomisation Best design for investigating treatments

45 Case series is a Cohort study with no comparison group Participants Exposure Group Outcomes Time P E C O T Allocated by measurement

46 Before-after study Participants Exposure Group Comparison Group Outcomes Time P C O T Allocated by timing of intervention E

47 Cross-over trial Participants Exposure Group 2 Comparison Group 2 Outcomes Time P C2C2 O T Allocated by randomisation E2E2 E1E1 C1C1 Exposure Group 1 Comparison Group 1

48 Cross-sectional study Participants Exposure GroupComparison Group Outcomes Time P E C O T Allocated by measurement real-life time best design for prevalence and diagnostic test accuracy

49 Diagnostic test accuracy study P EG CG O Disease +ve Test Disease -ve ab cd Likelihood +ve test if D+ve: EGO = a ÷ EG Likelihood +ve test if D -ve: CGO = a ÷ CG + -

50 Diagnostic test accuracy study P EG CG O Disease +ve Test Disease -ve ab cd Likelihood -ve test if D+ve: EGO = c ÷ EG Likelihood -ve test if D -ve: CGO = d ÷ CG + -

51 Diagnostic test for disease prediction P EG CG O Test +ve Disease Test -ve ab cd Likelihood of D if test +ve: EGO = a ÷ EG Likelihood of no D if test -ve CGO = d ÷ CG + - Positive predictive valueNegative predictive value

52 Diagnosis: test accuracy EG CG O Test ab cd + - P P CG EG Disease

53 Diagnosis: test accuracy EG CG O Test ab cd + - P P CG EG Disease Diagnosis: disease prediction

54 Case control study for investigating aetiology, interventions when outcomes rare ExposedNot Exposed Cases ab Controls cd

55 Case control study Exp.Not Exp. Cases ab Controls Participants Exp Group Comparison Group Outcomes Time P EG CG O T cases ‘nested in a virtual cohort study’ ab controls egcg

56 P Comparison E1E1 C E2E2 E3E3 Multiple Exposure categories Multiple Outcome categories GATE: multiple categories Participants

57 P Continuous measure of Outcomes e.g. lipids O low medium high high..med..low Continuous measure of Exposure: e.g. body mass index E Correlation coefficient GATE: continuous measurements Participants

58 Life is a non-randomised trial

59 The 6 steps of EBP 1.ASK a focussed question 2.ACCESS - search for epidemiological evidence to help answer question 3.APPRAISE the evidence for its validity, effect size, precision) 4.AGGREGATE the evidence with patient/community, clinical/hlth & policy issues & make an evidence- based decision 5.APPLY your decision 6.AUDIT your practice (i.e. check your actual practice against evidence-based practice). A CAT documents the steps for a specific question

60 CATS Download from

61 GATE-lite


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