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”