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

2. What is Evidence Based Practice?

3. What is Evidence Based Practice?

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

5. Graphic Approach To Epidemiology
The GATE frame
Graphic Approach To Epidemiology

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

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

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

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

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

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

12. Step 5
APPLY
Implementation!

13. 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

14. GATE Graphic Approach To Epidemiology
Graphic Appraisal Tool for Epidemiology
Graphic Architectural Tool for Epidemiology

15. the shape of every epidemiological study
The GATE frame
the shape of every epidemiological study

16. GATE study design (PECOT)

17. GATE study analyses (EGO & CGO)
EG CG a b c d

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

19. GATE study design (PECOT)
Participants
Exposure Group
Comparison Group
E C
Outcomes O
Time T

20. Participants
Study Setting
Eligible Participants P
Participants

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

22. Outcomes (O) a b c d
yes no
‘Dis-ease’ O
Outcomes (O)

23. Time (T)
incidence T
prevalence

25. GATE study analyses

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

27. GATE study analyses P O Overall Denominator Denominator 1:
Exposure Group EG
Denominator 2:
Comparison Group CG
EG CG
Numerator 1: a
Numerator 2: b a b c d O

28. Occurrence = N ÷ D P O Denominator 1: Exposure Group EG Denominator 2:
Comparison Group CG
EG CG
Numerator 1: a
Numerator 2: b a b c d O
Exposure Group Occurrence:
EGO = a ÷ EG
Comparison Group Occurrence:
CGO = b ÷ CG

29. 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

30. Analyses
it’s all about EGO & CGO

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

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

34. 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!’

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

36. appropriate Allocation process?
RAMBO P
appropriate Allocation process?
were EG & CG comparable
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
EG CG O T

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

38. did participants remain in allocated groups (EG & CG)
RAMBO P
good Maintenance?
did participants remain in allocated groups (EG & CG)
EG CG
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 O T

39. measurements & processes
RAMBO P
Blind or Objective?
measurements & processes A
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)
EG CG O T

40. 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

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

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

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

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

46. Cross-over trial P E1 C2 E2 C1 O T Participants
Allocated by randomisation
Exposure Group 1 E1 C2
Comparison Group 2
Exposure Group 2 E2 C1
Comparison Group 1
Outcomes O
Time T

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

48. Diagnostic test accuracy studyP
Disease +ve
EG CG
Disease -ve + a b c d
Test O -
Likelihood +ve test if D+ve:
EGO = a ÷ EG
Likelihood +ve test if D -ve:
CGO = a ÷ CG

49. Diagnostic test accuracy studyP
Disease +ve
EG CG
Disease -ve + a b c d
Test O -
Likelihood -ve test if D+ve:
EGO = c ÷ EG
Likelihood -ve test if D -ve:
CGO = d ÷ CG

50. Diagnostic test for disease prediction
Test +ve
EG CG
Test -ve + a b c d
Disease O -
Likelihood of D if test +ve:
EGO = a ÷ EG
Likelihood of no D if test -ve
CGO = d ÷ CG
Positive predictive value
Negative predictive value

51. Diagnosis: test accuracyP
Disease +
EG CG - +
Diagnosis: test accuracy + a b c d
CG EG O P - + - -
Test

52. Diagnosis: test accuracyP
Disease +
EG CG - +
Diagnosis: test accuracy + a b c d
CG EG O P - + - -
Test
Diagnosis: disease prediction

53. Case control study a b c d Exposed Not Exposed Cases Controls
for investigating aetiology, interventions when outcomes rare

54. Case control study P controls cases O T a b Participants
‘nested in a virtual cohort study’
Exp.
Not Exp.
Cases a b
Controls P
Participants
controls eg cg
Comparison Group
Exp Group
EG CG
cases a b O
Time T
Outcomes

55. GATE: multiple categories
Participants P C
Comparison
Multiple Exposure categories E1 E2 E3
Multiple Outcome categories

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

57. Life is a non-randomised trial

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

59. Download from www.epiq.co.nz
CATS
Download from

60. GATE-lite