Download - SCC 2012 Positively Uncertain (Amanda Burls)
Positively uncertainBritish Science AssociationScience Communication Conference 2012
Dr Amanda Burls
Director of Postgraduate Programmes in Evidence-Based Health Care
University of Oxford
In a traffic accident which would you prefer?
A. A team trained and equipped for advanced trauma life support to stabilise you in the field?
orB. A team trained and
equipped only for basic life support to take you as quickly as possible to the nearest A&E?
“Stay and Play”
“Scoop and Run”
The aim of teaching
“… to give an in-depth understanding of
the evidence-based approach to practice,
and the skills to translate these into the
effective care of patients and informed
health-care policies.”
First task: learn to recognise uncertainty
In a traffic accident which would you prefer?
A. ATLS?
Or
B. BLS?
“Stay and Play”
“Scoop and Run”
Systematic review of ATLS vs BLS
Liberman et al J Trauma 2000 49(4):584-599
15 papers reported mortalityDirection of research findings by quality of study:- Quality ATLS BLS
Fair 1 5 Good 1 1 Excellent 1 6
4 to 1 in favour of BLS!Combined –
Relative risk of death with ATLS: 2.92
Doctors by disposition and training want to act decisively…
Lots of examples where we got it wrong
Lack of research
Failure to systematically review studies
Failure to use evidence
“To be uncertain is uncomfortable, to be certain is ridiculous”
Chinese Proverb
“Education is the path from cocky ignorance to miserable uncertainty.”
Mark Twain
Objectives of Programme
Work comfortably in
situations of uncertainty and make sound judgements in the absence of definitive evidence.
unpredictable situations and deal with complex issues systematically and creatively
You don’t have to be superman to deal with uncertainties effectively!
UncertaintyIndividual ignorance
Not questioned
Not searched
Not foundPoor indexing
Poor searching skills
Behind paywall
Couldn’t make sense of what found
Unknown
Not researched
Researched but not written up
Written up but no up-to-date systematic review
Systematic review but…Primary studies biased
Results contradictory
Results inconclusive because lack of power
Would you want oxygen if you were having a heart attack?
Oxygen therapy for acute myocardial infarction. Cochrane Database Sys Rev 2010;6:CD007160
“The evidence is suggestive of harm but lacks power so this could be due to chance. Current evidence neither supports nor clearly refutes the routine use of oxygen in patients with acute myocardial infarction”.
Assuming the review was well-conducted, would you continue to give oxygen routinely to patients with a heart attack?
The right answer?“Should oxygen be given in myocardial infarction? On the basis of physiological reasons and no trial evidence of harm: YES.”
Atar D (editorial) BMJ 2010;340:c3287 (16 June)
“In the meantime, those who adhere to the advice to ´above all, do no harm´ would be best advised to avoid oxygen in patients with acute myocardial infarction, unless the patient has demonstrably low oxygen levels, and then only deliver sufficient to avoid hyperoxia.”
Weston C (editorial) The Cochrane Library 2010 (16 June)
Involve your patients as partners
“The only certainty is that nothing is certain.” Pliny the Elder
Probability
“When one admits that nothing is certain one must, I think, also admit that some things are much more nearly certain than others.”
Bertrand Russell
Teaching philosophy
“Tell me and I'll forget;
show me and I may remember;
involve me and I'll understand.”
1. This problem is rarely caused by a bacterial infection.
2. Our patients are often called by the x-ray department the morning after.
3. Sometimes we have nothing to do and the patient dies.
4. This inflammation typically causes recurrent episodes of wheezing.
5. Breathlessness is frequently present at night.
6. These symptoms are usually associated with widespread airflow limitation.
7. The airflow obstruction of asthma is generally reversible.
8. These symptoms are nonspecific, making asthma sometimes difficult to distinguish from other respiratory diseases.
9. This normally happens in otherwise strong boys.
10. The probable cause is Neisseria meningitidis.
0 10 20 30 40 50 60 70 80 90 100
Rarely
Often
Sometimes
Typically
Frequently
Usually
Generally
Normally
Sometimes
Probably
2012 (Range and Medians)
Oxford International Programme in Evidence-Based Health Care. Clinical Epidemiology
Uncertainty due to bias
“Tell me and I'll forget;
show me and I may remember;
involve me and I'll understand.”
I won’t really believe you
Teaching
“Tell me and I'll forget;
show me and I may remember;
involve me and I'll understand.”
I won’t really believe you
Teaching AND communicating with patients
Unconscious measurement bias
Be honest with patients about uncertainties
50
Childhood leukaemia in Pembroke Road between 1985-1994Cases observed = 5
Cases expected = 1
P < 0.0025
Relative Risk = 5.6
Uncertainty – a real example
Is this likely to be a cluster?
YesParents
Chief Executive
Chronicle and Echo
Dispatches
NoMe
Director of Public Health
DistrictNumber of Children
with leukaemia1969-88 1989-94
Age-standardised rates of leukaemia in children under15 per million children under 15
1969-1988 1989-1994Corby 12 2 44.3 31.4Daventry 10 3 38.3 39.5East Nhants 16 5 60.0 62.3Kettering 8 3 26.1 32.6Northampton 26 9 38.2 38.1South Nhants 19 5 64.0 58.6Wellingborough 15 2 52.4 24.1Northamptonshire 106 29 44.8 39.9England 7431 N/A 37.8 N/A
Age-standardised rates of childhood leukaemia in Northamptonshire
by District 1969-1988 and 1989-94, as available in 1995
It can’t be a coincidence
The Texas sharp-shooter error
No excess leukaemia!
The biggest danger in any cluster investigation is “generating” an apparently significant cluster when cases really occurred by chance
“Mobile phone mast causing brain cancer!”
Is there an excess number of cerebral cancers being caused by the telephone mast?
h
Advanced EBHC MSc students
During the “Swine Flu” epidemic pregnant women were advised to get vaccinated against the flu
Was the governments immunisation policy an over-reaction or a sensible public health policy?
Nearly everyone had a firmly held belief
What assumptions are you making?
Vaccination risky?
How risky would it have to be before it is not worth having?
Threshold number to vaccinate to prevent one death?
Weighing up sore arms against death or a bout of influenza?
Summary – teach peopleTo recognise uncertainties
Intuition & pathological reasoning are unreliable
Good intentions can do more harm than good
Stick to where there is evidence of net benefit, or
Do them in way in which they can be evaluated
Find, appraise and integrate evidence efficiently
If “certain” be explicit about assumptions
Involve patients
Don’t be afraid to say “I don’t know”