Lecture 1
Recognising and
capturing clinical
uncertainty
Dr Carl Thompson, University of York
Foreground and background
knowledge
foreground
knowledge
Background
knowledge
Expertise and decision making
Dr Carl Thompson, University of York
clarification
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Clinical uncertainty
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Clinical judgement
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Clinical decision making
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Evidence based decision making
Dr Carl Thompson, University of York
Clinical uncertainty
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Not certainly knowing or known
Sources
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Defining a disease
Making a diagnosis
Selecting an intervention
Observing outcomes
Assessing patient preferences
Combing information in a decision
Dr Carl Thompson, University of York
Quantifying Uncertainty
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True state of the patient cannot be directly
observed
Clinician must use imperfect external cues
Probability as a language for expressing
uncertainty
Dr Carl Thompson, University of York
Probability Fundamentals
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Strength of belief
A number between 0 and1 that expresses an
opinion about the likelihood of an event
Probability of an event that is certain to occur is 1
Probability of an event that is certain to NOT occur
is 0
Dr Carl Thompson, University of York
Types of probability
Term
definition
Formula range
Probability
The chance of an event
P
0-1
Proportion
relative frequency of a state
P
0-1
Prevalence
The proportion of a group with a specific
disease
P
0-1
Percentage
Probability expressed as a frequency per 100
P x 100
0-100
Frequency
Probability expressed per sample (1 per 1000)
P
0–
denomi
nator
Odds
Ratio of the probability of an event to its
complement
P(/1-P)
0infinity
Incidence rate
Occurrence of new disease cases
P/t
0infinity
Incidence
proportion
The proportion of people who develop a new
disease or event during a period of time
P
0-1
Risk
The probability that an individual develops a
new disease during or event a specified period
of time Dr Carl Thompson, University of York
P
0-1
Components of Probability Estimates
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Personal experience
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Published experience - evidence
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Attributes of the patient
Dr Carl Thompson, University of York
Clinical decision and judgement
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Clinical judgement
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Assessment of alternatives
Clinical decision
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Choosing between alternatives
(Dowie 1988)
Dr Carl Thompson, University of York
The decisions clinicians make.
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Diagnosis and test ordering (Dx)
Treatment (Rx)
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Targeting
Timing
referral
Communicating (risks and benefit info)
Seeking more information
S.D.O. (service delivery and organisation)
Dr Carl Thompson, University of York
Clinical uncertainty – the good
news
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Aeschylus – ‘hope comes from the lack of
certainty of fate’
Complete certainty = lack of hope
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Examination results predicted life success
(100% accurately)
Learning at age 12 that you possess the
Alzheimer’s gene
Adaptation to Huntington’s and HIV status
Dr Carl Thompson, University of York
Asking questions
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Background questions:
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General knowledge about a disorder
A root (who, what, when, how, and why) a
verb
A disorder or aspect of a disorder
E.g. ‘what causes angina?’
Dr Carl Thompson, University of York
Foreground questions P.I.C.O.
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Specific knowledge about management of people
with a disorder
Population: the people who are on the receiving end of
your judgement and choices
Intervention: that which you are thinking of doing to
(with?) them
Counter intervention: the other choices – nb.
sometimes not in a question when no choice
Outcome: what do you want see happen (or not
happen) as a result of your choice?
Dr Carl Thompson, University of York
Population - Can Include:
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Disease or condition
Sex, age, race, socio-economic
setting
Stage of disease, care setting
Dr Carl Thompson, University of York
Interventions - Can Include:
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General or specific interventions
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Level of intervention
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Frequency/dosage
Stage of intervention
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treatment options or specific drug, risk factors or
specific cause
prevention, secondary prevention, early, advanced
Delivery of intervention
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setting, professional group, self-medication
Dr Carl Thompson, University of York
Comparisons With The Intervention Can Include:
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Standard practice
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Gold standard intervention
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Placebo
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Other specific comparisons
Dr Carl Thompson, University of York
Outcomes - Can Include:
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Clinical Outcomes
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Provider-oriented Outcomes
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mortality, reduction of symptoms, adverse
effects
cost-effectiveness, benefits to service
Patient-oriented Outcomes
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QoL, satisfaction, acceptance
Dr Carl Thompson, University of York
Why bother with PICO?
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Helps focus scarce learning time on relevant
evidence for patient need
Helps focus scarce learning time on evidence
that addressed your knowledge needs
Suggests high yield search strategies
Suggest the form useful answers might take
Aid referrals by clearly communicating needs
As a basis for teaching others (clarity in
communication)
Leads to answers  increases your motivation
Dr Carl Thompson, University of York
Some examples
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Is sucrose a safe and effective analgesic during painful
procedures in newborns?
Do prenatal and postnatal home visits by nurses have long
term effects on maternal and child outcomes?
Do transparent polyurethane dressings reduce
dislodgement, phlebitis, and “tissuing” of peripheral IV
catheters compared to gauze?
Is exposure to parental tobacco smoke associated with an
increased risk of asthma in school age children?
Dr Carl Thompson, University of York
Your go!
population
intervention
Counter
intervention
Dr Carl Thompson, University of York
Outcome
Intro to a Search Strategy:
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Start with a clear answerable
question
Break the question down into
concepts
Search each concept separately
(use indexing terms, other indexing
features, textwords]
Combine terms
Limit results
Dr Carl Thompson, University of York
Searching For Individual Concepts:
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Indexing terms (thesaurus terms, subject
headings)
eg. MeSH
mapping
Textwords
synonyms
alternative spellings and word endings
truncation (usually $ or *) eg. manag$
proximity operators [usually adj# or near#] eg. home
adj3 help
exact phrase [usually “ # ”] eg. “clinical governance”
Dr Carl Thompson, University of York
Combining concepts
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AND - Creates a smaller set; both concepts must be present. In
this case the result set is the records which contain both the
smoking and counselling concepts.
Smoking
Result set
Counselling
Dr Carl Thompson, University of York
Combining concepts
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OR - Creates a larger set; any or all concepts must be present. Used to link
similar concepts. In this case the result set is the records which contain both
the psychotherapy and counselling concepts (all the blue area)
Psychotherapy
Counselling
Dr Carl Thompson, University of York
Combining concepts
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NOT - Excludes a concept. Used to remove specific concepts. In this case
the result set is the records which contain tobacco but not those which also
contain snuff (yellow hatched area). Use with care because it can have
unexpected results.
Snuff
Tobacco
Dr Carl Thompson, University of York
Example search, using MEDLINE subject headings
#1 substance use disorders/
#2 exp substance dependence/
#3 drug adj addiction
#4 or/1-3
#5 exp child/
#6 teenager? or adolescent? or young adj people
#7 or/5-6
#8 exp health promotion/
#9 prevent? adj (campaign? or program? or activit?)
#10 or/8-9
#11 4 and 7 and 10
Dr Carl Thompson, University of York