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Dr Carl Thompson, University of York Lecture 1 Lecture 1 Recognising and Recognising and capturing clinical capturing clinical uncertainty uncertainty
Dr Carl Thompson, University of York
Lecture 1Lecture 1Recognising and Recognising and capturing clinical capturing clinical
uncertaintyuncertainty
Dr Carl Thompson, University of York
Foreground and background Foreground and background knowledgeknowledge
Background knowledge
foreground knowledge
Expertise and decision making
Dr Carl Thompson, University of York
clarificationclarification Clinical uncertaintyClinical uncertainty
Clinical judgementClinical judgement
Clinical decision makingClinical decision making
Evidence based decision makingEvidence based decision making
Dr Carl Thompson, University of York
Clinical uncertaintyClinical uncertainty Not Not certainly certainly knowing or knownknowing or known SourcesSources
Defining a diseaseDefining a disease Making a diagnosisMaking a diagnosis Selecting an interventionSelecting an intervention Observing outcomesObserving outcomes Assessing patient preferencesAssessing patient preferences Combing information in a decisionCombing information in a decision
Dr Carl Thompson, University of York
Quantifying UncertaintyQuantifying Uncertainty
True state of the patient cannot be directly True state of the patient cannot be directly observedobserved
Clinician must use imperfect external cuesClinician must use imperfect external cues
Probability as a language for expressing Probability as a language for expressing uncertaintyuncertainty
Dr Carl Thompson, University of York
Probability FundamentalsProbability Fundamentals
Strength of beliefStrength of belief
A number between 0 and1 that expresses an A number between 0 and1 that expresses an opinion about the likelihood of an eventopinion about the likelihood of an event
Probability of an event that is certain to occur is 1Probability of an event that is certain to occur is 1
Probability of an event that is certain to NOT Probability of an event that is certain to NOT occur is 0occur is 0
Dr Carl Thompson, University of York
Types of probabilityTypes of probabilityTerm definition Formul
arange
ProbabilityProbability The chance of an eventThe chance of an event PP 0-10-1ProportionProportion relative frequency of a state relative frequency of a state PP 0-10-1PrevalencePrevalence The proportion of a group with a specific The proportion of a group with a specific
diseasediseasePP 0-10-1
PercentagePercentage Probability expressed as a frequency per Probability expressed as a frequency per 100100
P x 100P x 100 0-1000-100
FrequencyFrequency Probability expressed per sample (1 per Probability expressed per sample (1 per 1000)1000)
PP 0 – 0 – denomdenominatorinator
Odds Odds Ratio of the probability of an event to its Ratio of the probability of an event to its complementcomplement
P(/1-P)P(/1-P) 0-0-infinityinfinity
Incidence rate Incidence rate Occurrence of new disease casesOccurrence of new disease cases P/tP/t 0-0-infinityinfinity
Incidence Incidence proportionproportion
The proportion of people who develop a The proportion of people who develop a new disease or event during a period of new disease or event during a period of time time
PP 0-10-1
Risk Risk The probability that an individual The probability that an individual develops a new disease during or event develops a new disease during or event a specified period of time a specified period of time
PP 0-10-1
Dr Carl Thompson, University of York
Components of Probability EstimatesComponents of Probability Estimates
Personal experiencePersonal experience
Published experience - evidencePublished experience - evidence
Attributes of the patientAttributes of the patient
Dr Carl Thompson, University of York
Clinical decision and judgementClinical decision and judgement Clinical judgementClinical judgement
Assessment of alternativesAssessment of alternatives
Clinical decision Clinical decision
Choosing between alternativesChoosing between alternatives
(Dowie 1988)(Dowie 1988)
Dr Carl Thompson, University of York
The decisions clinicians make.The decisions clinicians make. Diagnosis and test ordering (Dx)Diagnosis and test ordering (Dx) Treatment (Rx)Treatment (Rx)
TargetingTargeting TimingTiming referralreferral
Communicating (risks and benefit info)Communicating (risks and benefit info) Seeking more informationSeeking more information S.D.O. (service delivery and S.D.O. (service delivery and
organisation)organisation)
Dr Carl Thompson, University of York
Clinical uncertainty – the good Clinical uncertainty – the good newsnews
Aeschylus – ‘hope comes from the Aeschylus – ‘hope comes from the lack of certainty of fate’ lack of certainty of fate’
Complete certainty = lack of hopeComplete certainty = lack of hope Examination results predicted life Examination results predicted life
success (100% accurately)success (100% accurately) Learning at age 12 that you possess the Learning at age 12 that you possess the
Alzheimer’s geneAlzheimer’s gene Adaptation to Huntington’s and HIV Adaptation to Huntington’s and HIV
statusstatus
Dr Carl Thompson, University of York
Asking questionsAsking questions Background questions:Background questions:
General knowledge about a disorder General knowledge about a disorder A root (who, what, when, how, and why) A root (who, what, when, how, and why)
a verb a verb A disorder or aspect of a disorderA disorder or aspect of a disorder E.g. ‘what causes angina?’E.g. ‘what causes angina?’
Dr Carl Thompson, University of York
Foreground questions P.I.C.O.Foreground questions P.I.C.O. Specific knowledge about management of people Specific knowledge about management of people
with a disorder with a disorder
PopulationPopulation: the people who are on the receiving end of : the people who are on the receiving end of your judgement and choicesyour judgement and choices
InterventionIntervention: that which you are thinking of doing to : that which you are thinking of doing to (with?) them (with?) them
Counter interventionCounter intervention: the other choices – : the other choices – nb. sometimes nb. sometimes not in a question when no choicenot in a question when no choice
OutcomeOutcome: what do you want see happen (or not happen) : what do you want see happen (or not happen) as a result of your choice?as a result of your choice?
Dr Carl Thompson, University of York
Population - Can Include:Population - Can Include:
Disease or condition Disease or condition
Sex, age, race, socio-economic Sex, age, race, socio-economic setting setting
Stage of disease, care settingStage of disease, care setting
Dr Carl Thompson, University of York
Interventions - Can Include:Interventions - Can Include:
General or specific interventions General or specific interventions treatment options or specific drug, risk factors treatment options or specific drug, risk factors
or specific cause or specific cause Level of intervention Level of intervention
Frequency/dosage Frequency/dosage Stage of intervention Stage of intervention
prevention, secondary prevention, early, prevention, secondary prevention, early, advanced advanced
Delivery of intervention Delivery of intervention setting, professional group, self-medicationsetting, professional group, self-medication
Dr Carl Thompson, University of York
Comparisons With The Intervention - Comparisons With The Intervention - Can Include:Can Include:
Standard practice Standard practice
Gold standard intervention Gold standard intervention
Placebo Placebo
Other specific comparisonsOther specific comparisons
Dr Carl Thompson, University of York
Outcomes - Can Include:Outcomes - Can Include: Clinical Outcomes Clinical Outcomes
mortality, reduction of symptoms, mortality, reduction of symptoms, adverse effects adverse effects
Provider-oriented Outcomes Provider-oriented Outcomes cost-effectiveness, benefits to service cost-effectiveness, benefits to service
Patient-oriented Outcomes Patient-oriented Outcomes QoL, satisfaction, acceptanceQoL, satisfaction, acceptance
Dr Carl Thompson, University of York
Why bother with PICO?Why bother with PICO? Helps focus scarce learning time on Helps focus scarce learning time on relevant relevant
evidence for patient needevidence for patient need Helps focus scarce learning time on evidence Helps focus scarce learning time on evidence
that addressed your knowledge needsthat addressed your knowledge needs Suggests high yield search strategiesSuggests high yield search strategies Suggest the form useful answers might take Suggest the form useful answers might take Aid referrals by clearly communicating needsAid referrals by clearly communicating needs As a basis for teaching others (clarity in As a basis for teaching others (clarity in
communication)communication) Leads to answers Leads to answers increases your motivation increases your motivation
Dr Carl Thompson, University of York
Some examplesSome examples 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!Your go!population intervention Counter
interventionOutcome
Dr Carl Thompson, University of York
Intro to a Search Strategy:Intro to a Search Strategy:
Start with a clear answerable Start with a clear answerable question question
Break the question down into Break the question down into concepts concepts
Search each concept separately Search each concept separately (use indexing terms, other (use indexing terms, other
indexing features, textwords] indexing features, textwords] Combine terms Combine terms Limit resultsLimit results
Dr Carl Thompson, University of York
Searching For Individual Concepts:Searching For Individual Concepts:
Indexing terms (thesaurus terms, subject Indexing terms (thesaurus terms, subject headings) headings)
eg. MeSH eg. MeSH mapping mapping Textwords Textwords synonyms synonyms alternative spellings and word endings alternative spellings and word endings truncation (usually $ or *) eg. manag$ truncation (usually $ or *) eg. manag$ proximity operators [usually adj# or near#] eg. proximity operators [usually adj# or near#] eg.
home adj3 help home adj3 help exact phrase [usually “ # ”] eg. “clinical exact phrase [usually “ # ”] eg. “clinical
governance”governance”
Dr Carl Thompson, University of York
Combining conceptsCombining concepts AND - Creates a smaller set; both concepts must AND - Creates a smaller set; both concepts must
be present. In this case the result set is the be present. In this case the result set is the records which contain both the smoking and records which contain both the smoking and counselling concepts.counselling concepts.
Result setSmoking
Counselling
Dr Carl Thompson, University of York
Combining conceptsCombining concepts OR - Creates a larger set; any or all concepts must be OR - Creates a larger set; any or all concepts must be
present. Used to link similar concepts. In this case the present. Used to link similar concepts. In this case the result set is the records which contain both the result set is the records which contain both the psychotherapy and counselling concepts (all the blue area)psychotherapy and counselling concepts (all the blue area)
Psychotherapy
Counselling
Dr Carl Thompson, University of York
Combining conceptsCombining concepts NOT - Excludes a concept. Used to remove specific NOT - Excludes a concept. Used to remove specific
concepts. In this case the result set is the records which concepts. In this case the result set is the records which contain tobacco but not those which also contain snuff contain tobacco but not those which also contain snuff (yellow hatched area). Use with care because it can have (yellow hatched area). Use with care because it can have unexpected results.unexpected results.
Snuff
Tobacco
Dr Carl Thompson, University of York
Example search, using MEDLINE Example search, using MEDLINE subject headings subject headings
#1 substance use disorders/#1 substance use disorders/#2 exp substance dependence/#2 exp substance dependence/#3 drug adj addiction#3 drug adj addiction#4 or/1-3#4 or/1-3#5 exp child/#5 exp child/#6 teenager? or adolescent? or young adj people#6 teenager? or adolescent? or young adj people#7 or/5-6#7 or/5-6#8 exp health promotion/#8 exp health promotion/#9 prevent? adj (campaign? or program? or activit?)#9 prevent? adj (campaign? or program? or activit?)#10 or/8-9#10 or/8-9#11 4 and 7 and 10#11 4 and 7 and 10
