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Rod Jackson EPIQ group University of Auckland, NZ GATE: EBP with pictures © a Graphic Approach to Teaching EBP a Graphic Appraisal Tool.

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Presentation on theme: "Rod Jackson EPIQ group University of Auckland, NZ GATE: EBP with pictures © a Graphic Approach to Teaching EBP a Graphic Appraisal Tool."— Presentation transcript:


2 Rod Jackson EPIQ group University of Auckland, NZ GATE: EBP with pictures © a Graphic Approach to Teaching EBP a Graphic Appraisal Tool for EBP Graphic Architectural Tool for Epidemiology 5/9/05 Oxford

3 What is evidence-based practice (EBP)? Evidence ways of knowing Practitioner Policy Patient

4 Practitioner Policy Patient What is evidence-based practice? Evidence ways of knowing

5 n more comprehensively (systematic reviews) n more critically (evidence appraisals) n more quantitatively (probabilities) using more evidence from clinical epidemiology (on diagnosis, prognosis & interventions) to inform decisions What is evidence-based practice?

6 What is the evidence of EBP? clinically relevant evidence, sometimes from basic science, but especially from patient-centred clinical research into the accuracy of diagnostic tests*, the power of prognostic markers*, and the efficacy & safety of interventions* Modified from Sackett et al. EBM 2nd Edition 2000 * from clinical epidemiological studies

7 Epidemiological evidence is the cornerstone of EBP understanding epidemiological study design is the essential skill for teachers of EBP

8 The 4 (5) steps of EBP 1.Ask a focussed clinical question 2.Search for appropriate epidemiological evidence to help answer question 3.Appraise (critically) the evidence (validity, impact, precision) 4.Synthesise the evidence with patient, clinical & policy issues; then apply (i.e. answer question) 5.Assess/ evaluate practice (clinical audit). Modified from DS et al

9 CATs: Critically Appraised Topics: a tool for modeling the steps of EBP

10 CAT forms: (in Excel) Intervention Diagnosis Prognosis/Risk (coming) Systematic Reviews (coming) download from:

11 GATE: Graphic Appraisal Tool for Epidemiology The GATE Approach: every epidemiological study hangs on the GATE frame there is only one study design: RCT - interventions Cohort studies - prognosis / interv./ aetiology Cross-sectional studies - diagnosis Case-control studies - interv./aetiol.

12 P EC O GATE: Graphic Appraisal Tool for Epidemiology T © GATE Frame: PECOT Population Exposure Comparison Outcome Time

13 PopulationP © GATE: epi study design (P)

14 Participant Population: Source Population: Eligible Population: 68,561 women screened from 20 outpatients/community screening centres all eligibles invited (2763) Post-menopausal, established CHD, < 80 yrs, no MI in last 6 mths, no HRT last 3 months P

15 PopulationP Comparison (C) [control] EC Exposure (E) [or intervention] © GATE: epi study design (E&C)

16 HRT Comparison (C) [control] EC Exposure (E) [or intervention] Identical Placebo

17 PopulationP Comparison EC Outcomes (O) O yes no Exposure ab cd © GATE: epi study design (O)

18 1º CHD Outcomes (O) O yes no EC

19 mean HDL cholesterol (mmol/L) Outcomes (O) 1.4 HRTPlacebo 1.27

20 PopulationP Comparison EC Outcomes Time (T) T O Exposure © GATE: epi study design (T)

21 EC CHD measured over 4.1 years (longitudinal) Time (T) T O

22 EC HDL cholesterol measured at 1 year (cross-sectional) Time (T) T O

23 PopulationP Comparison E1E1 C E2E2 E3E3 Multiple Exposure categories © Multiple Outcome categories GATE: epi study design

24 PopulationP 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: epi study design

25 PopulationP Exposure GroupComparison Group non- randomised allocation Outcomes O Life is a cohort study: a natural experiment Cohort (Follow-up) study: archetypal epidemiological study Time T Real life time EGEGCGCG cohort ill-health ©

26 PopulationP Cohort of women diagnosed with breast cancer childbirth <2yrs before diagnosis Non-randomised allocation to prognostic groups yes death. no O Cohort study (prognosis): Danish Breast Cancer Cooperative 10 years T EGEGCGCG No childbirth <2 yrs before diagnosis © Kroman et al. BMJ 1997;315:851-5

27 PopulationP Cohort of British Doctors established in 1951 Smokers Non-smokers Non-randomised allocation (self- reported smoking) yes Lung Cancer. no O Cohort study (aetiology): British Doctors Study T EGEGCGCG 50 years © Doll et al. BMJ 2004;328:1519

28 PopulationP Cohort of US Nurses HRT No HRT Non-randomised allocation (self- reported use) yes CHD. no O Cohort study (intervention): Nurses Health Study T EGEGCGCG 10 years © Stampfer et al. NEJM 1991;325:756-62

29 PopulationP Outcomes: CHD O Randomised Controlled Trial (RCT): HERS Time T Randomised allocation EGEGCGCG Exposure ( intervention ): HRT Comparison ( control ): Placebo © Hulley et al. JAMA1998;280:605-13

30 PopulationP EGEGC No one allocated to Comparison Group Outcomes O Time Case series T Exposure Grp ©

31 PopulationP Comparison Grp CGCG Allocation: randomised or non-randomised Outcomes O Before-After Study (& cross-over study) Time T Exposure Grp EGEG ©

32 PopulationP O Time ? Cross-sectional (prevalence) study/survey: PECO E/C assignment & Outcomes assessed in cohort at same Time EGEGCGCG EGEGCGCG Real life time © O LTPA angina LTPA

33 PopulationP + Test Outcomes. - O Time Diagnostic Test Accuracy Study (cross-sectional) EG: Gold Standard +ve CG: Gold Standard -ve EGEGCGCG GS+GS- d c b a Allocation by measurement ©

34 PopulationP +ve predictive value. O Time Diagnostic Test Study Application (cross-sectional) EG: Test +ve CG: Test -ve EGEGCGCG T+T- d c b a Allocation by measurement © -ve predictive value.

35 PopulationP= Outcomes a= GATE: the NUMBERS Time T= EG=CG= Exposure GroupComparison Group b= c=d= ©

36 Population P= 2763 Outcomes a= 172 GATE: the numbers = HERS Time T= 4.1 yrs EG= 1380 Exposure GroupComparison Group © CG= 1383 b= 176

37 P= a= Epidemiology = numerator / denominator (E=N/D) EG=CG= Denominators = EG x T and CG x T b= c=d= Numerators = a or c and b or d © Population sub-populations outcomes Occurrence = outcome / population T + -

38 P= a= GATE: occurrence = numerator / denominator EG=CG= Exp. Group Occurrence EGO = a / EG x T b= c=d= Comp. Group Occurrence CGO = b / CG x T © T= EGO = c / EG x T EGO = d / EG x T

39 GATE: occurrence HERS Exp. Group Occurrence EGO = A / EGxT = 172/1380 x 4.1 = 30.40/1000/yr Comp. Group Occurrence CGO = B / CGxT = 176/1383 x 4.1 = 31.04/1000/yr P= 2763 A= 172 EG= 1380 CG= 1383 B= 176 T= 4.1 yrs


41 Occurrence EGO = Exposure Group Occurrence (A/[EGxT]) CGO = Comparison Group Occurrence (B/[CGxT] = / 1000 persons / year

42 Effects: comparing occurrences Relative Effect/Risk (RR) = EGO CGO e.g. relative risk, risk ratio, prevalence ratio, incidence ratio Absolute Effect/Risk Difference (RD) = EGO - CGO e.g. risk difference, absolute risk Number Needed to Treat (NNT) to prevent/cause 1 event = 1/RD

43 Using GATE to frame all the steps of EBP

44 STEP 1: Ask focussed 5-part questions: 1. P articipants (patient/population group) 2. E xposure (intervention if about therapy) 3. C omparison (there is always an alternative!) 4. O utcome 5. T imeframe

45 STEP 2: Search for best evidence using 3/4-part search terms: 1. P articipants (patient/population group) 2. E xposure (intervention if about therapy) 3. C omparison (e.g placebo) 4. O utcome

46 P EC Step 3a: appraise the evidence - hang the study & numbers on the GATE frame: PECOT T O Population Exposure © Comparison Outcome Time

47 P EC Step 3b:appraise the evidence: did the right people get in the right places? RAMM T O Representative of who? Allocated appropriately? © Measured well? - blinded or objective -complete

48 R A M M

49 EBCP Step 4: applying the evidence - the X-factor ©

50 Epidemiologic evidence clinical considerations Policy issues Patient preferences X-factor: making evidence-based decisions X-factor: integrating everything clinical expertise: other ways of knowing

51 Step 4

52 RAM the evidence based practitioner

53 the CAT: a tool for life long learning

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