David Spiegelhalter, Cambridge University - #steps13
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Transcript of David Spiegelhalter, Cambridge University - #steps13
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Communicating Risk and Uncertainty
Case study in breast-cancer screening
“Scales of uncertainty”
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Benefits and harms of cancer screening
• ‘Shared-care’ and ‘informed choice’• New leaflet will present pros and cons• Will not make recommendation
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Citizen’s ‘Jury’
• Scientific review used evidence to try to answer question
‘What is the effect of being invited for screening?’
• But relevant question for women is ‘What is the effect of attending screening’
• Preferred ‘over-treatment’ to ‘over-diagnosis?’ etc
• Etc etc
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Uncertainty
But these numbers are very uncertain!
Full of ‘conditionalities’
Not quantifiable as a confidence interval
Best current estimate, but may change
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Words of Estimative Probability (WEP)
• NIC scale of likelihood and confidence
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How can we communicate deeper uncertainties due to the quality of the evidence?
Part of GRADE scale used in Cochrane Collaboration and 25 other organisations to assess confidence in estimates of medical treatment effects
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Sandman’s 4 conclusions
1.Don’t just acknowledge the uncertainty, proclaim it
2. Proclaim how uncertain you are – from – “I’m taking a shot in the dark here” to – “I’m almost certain but there are still a few
remaining doubts to clear up.”
3. Distinguish your level of uncertainty now from the level of uncertainty earlier
4. Come across as human
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1990: John Gummer – ‘beef is safe’
1992: three cows in every 1,000 in Britain had BSE
1996: government admits link between BSE and the human form of the disease, new variant CJD