GATE: Graphic Appraisal Tool for Epidemiology 1991-2015 1 picture, 2 formulas & 3 acronyms 1
GATE: Graphic Appraisal Tool for Epidemiology Graphic Architectural Tool for Epidemiology Graphic Approach To Epidemiology making epidemiology accessible 2
presentation outline GATE is a framework for: 1. study design 2. study analysis 3. study error 4. practicing EBM 1 picture, 2 formulas & 3 acronyms 3
GATE: a framework for study design 1 picture every epidemiological study can be hung on the GATE frame 1 picture, 2 formulas & 3 acronyms 5
cohort of British doctors 1 picture: GATE frame smoking status allocated by measurement (observation) smokers non-smokers lung cancer events counted yes no followed for 10 years cohort / longitudinal / follow-up study 1 picture, 2 formulas & 3 acronyms 6
1 st acronym: PECOT British doctors P Participants randomly allocated to aspirin or placebo Exposure aspirin E C Comparison placebo Outcomes yes MI no O Time 5 years randomised controlled trial T 1 picture, 2 formulas & 3 acronyms 7
middle-aged Americans P body mass index measured overweight E C normal weight diabetes status measured in all participants yes no O T cross-sectional (prevalence) study 8
middle-aged American women P receive mammogram screening test mammogram positive E C mammogram negative breast cancer yes no O T diagnostic test (prediction) study 9
middle-aged American women P Gold Standard breast cancer E C no breast cancer mammogram test positive negative O T diagnostic (test accuracy) study 10
P smokers E C non-smokers lung cancer smoking status measured yes no O cases controls T case-control study (all nested in virtual cohort studies) 11
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GATE: a framework for study analysis: 1 st formula: occurrence = outcomes population the numbers in epidemiological studies can be hung on the GATE frame 1 picture, 2 formulas & 3 acronyms 14
1 st formula: occurrence of outcomes = number of outcomes number in population/group British doctors P Participant Population smoking status measured Exposure Group smokers EG CG Comparison Group non-smokers Outcomes Lung cancer yes no a O b T Time 10 years 15
British doctors P Population smoking status measured Exposure Group smokers EG CG Comparison Group non-smokers Outcomes Lung cancer yes no a O b T Time 10 years Exposure Group Occurrence (EGO) = a EG = number of outcomes (a) number in exposed population (EG) 16
British doctors P Population randomly allocated Exposure Group aspirin EG CG Comparison Group placebo Outcomes MI yes no a O b T Time 5 years Comparison Group Occurrence (CGO) = b CG = number of outcomes (b) number in comparison population (CG) 17
Epidemiology = Numerator Denominator middle-aged American women P Participant Population Exposure Group mammogram positive Outcomes breast cancer receive mammogram screening test yes no EG D a N O Comparison Group mammogram negative T Time 18
the goal of all epidemiological studies is to calculate EGO and CGO British doctors P smoking status measured smokers EG CG non-smokers EGO: Occurrence (risk) of cancer in smokers yes no a O b Lung cancer 10 years T CGO: Occurrence of cancer in nonsmokers 19
Middle-aged Americans P Body Mass Index (BMI) measured High BMI EG CG Low BMI EGO: Average blood glucose in EG high low O CGO: Average blood glucose in CG 20
Middle-aged American women P Gold Standard Breast cancer E C no Breast cancer mammogram positive negative EGO: likelihood of a positive mammogram if breast cancer O T CGO: likelihood of a positive mammogram if no breast cancer 21
1 st formula: occurrence = outcomes population its all about EGO and CGO EGO CGO = Relative Risk (RR) EGO CGO = Risk Difference (RD) measures of occurrence: risk; rate; likelihood; probability; average; incidence; prevalence 22
GATE: framework for nonrandom error 2 nd acronym: RAMBOMAN Recruitment Allocation Maintenance Blind Objective Measurements ANalyses 1 picture, 2 formulas & 3 acronyms 24
Study setting Eligible population recruitment process P P RAMBOMAN Recruitment of participants who are the findings applicable to? 25
RAMBOMAN: were participants well Allocated to exposure & comparison groups? was Allocation to EG & CG successful? RCT: allocated by randomisation (e.g to drugs) Cohort: allocated by measurement (e.g. smoking) EG & CG similar at baseline? EG CG EG CG E & C measures accurate? T O T O 26
P RAMBOMAN were Participants well Maintained in the groups they were allocated to? T EG CG O completeness of follow-up compliance contamination co-interventions 27
P RAMBOMAN were outcomes well Measured? EG CG were they measured Blind to whether participant was in EG or CG? T O 28
P RAMBOMAN were outcomes well Measured? EG CG were they measured Objectively? T O 29
P RAMBOMAN were the ANalyses done well? EG A CG A EG C CG C If RCT were Intention To Treat (ITT) analyses done? T a O b 30
P RAMBOMAN were the ANalyses done well? EG CG adjustment for baseline differences / confounding? T O 31
GATE: random error: 2 nd formula: random error = 95% confidence interval EGO ± 95% CI CGO ± 95% CI There is about a 95% chance that the true value in the underlying population lies within the 95% CI (assuming no non-random error) 1 picture, 2 formulas & 3 acronyms 32
GATE: a framework for error in systematic reviews & meta-analyses: 3 rd acronym: FAITH 1 picture, 2 formulas & 3 acronyms 33
systematic review: a study of studies study sources studies screened studies appraised & allocated: included excluded studies summarised & pooled if homogeneous 34
critical appraisal of SR: FAITH Find study sources studies screened Appraise studies appraised & allocated: Include included excluded Total Heterogeneity? studies summarised & pooled if homogeneous 35 1 picture, 2 formulas & 3 acronyms
GATE: framework for the 4 steps of Evidence Based Practice (EBP) 37
the steps of EBP: 1. Ask 2. Access 3. Appraise 4. Apply & Act 38
EBP Step 1: ASK - turn your question into a focused 5-part PECOT question P 1. Participants 2. Exposure E C 3. Comparison 4. Outcomes yes no O T 5. Time 39
EBP Step 2: ACCESS the evidence use PECOT to help choose search terms P Participants Exposure E C Comparison Outcomes yes no O T Time 40
EBP Step 3: APPRAISE the evidence with the picture, acronyms & formulas P E C E P C Recruitment Allocation Maintenance blind O T T O objective Measurements ANalyses Occurrence = outcomes population Random error = 95% Confidence Interval 41
APPLY the evidence by AMALGAMATING the relevant information & making an evidencebased decision: the X-factor 42
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X-factor: making evidence-based decisions person family community practitioner values & preferences epidemiological evidence patient s clinical circumstances system features economic legal political Practitioner expertise: putting it all together - the art of practice Clinical expertise in the era of evidence-based medicine and patient choice. EBM 2002;736-8 (March/April) 44
GATE critically appraised topic (CATs) forms
GATE CAT 3-sheet workbook (in Excel) sheet 1: GATE-Ask & Access 46
GATE CAT 3-sheet workbook (in Excel) sheet 2: GATE-Appraise (with calculator) 47
GATE CAT 3-sheet workbook (in Excel) sheet 3: GATE-Apply 48