Alastair Hay, Consultant Senior Lecturer in Primary Health Care
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Transcript of Alastair Hay, Consultant Senior Lecturer in Primary Health Care
Alastair Hay, Consultant Senior Lecturer in Primary Health Care
The TARGET Programme: strengths, weaknesses, opportunities and lessons
learned (so far).
What is the problem?• High rates of RTIs in children lead to
• Economic burden to health services and parents (and their employers)
• Unnecessary use of antibiotics leads toIncreased selective pressure on antimicrobial
resistance andMedicalisation of illness vicious or virtuous circle
• Clinical uncertainty drives use but leads to low specificity
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What does the TARGET team believe is the solution?
• Clinical prediction rule?• Yes, but…
What to “predict” (diagnosis vs. prognosis)? Which symptoms and signs to measure? How would a prediction rule fit into current clinical
practice (simple vs. complex intervention)?
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Programme overview4
Parent Clinician Child
WS2* - Qualitative studies
Parent knowledge, health seeking behaviour
and information needs
WS1* - Systematic reviews
a) Factors associated with frequent attendance b) Natural history of RTI symptoms in childhood;
WS3* - Prospective cohort study
Clinical (and microbiological) factors associated with poor
prognosis to derive and validate a clinical rule to
predict hospitalisation from RTI
WS4* - cluster randomised controlled
trial Clinical and cost effectiveness of clinical
rule + parent information
Years 1
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Programme overview5
Parent Clinician Child
WS2* - Qualitative studies
Parent knowledge, health seeking behaviour
and information needs
WS1* - Systematic reviews
a) Factors associated with frequent attendance b) Natural history of RTI symptoms in childhood;
WS3* - Prospective cohort study
Clinical (and microbiological) factors associated with poor
prognosis to derive and validate a clinical rule to
predict hospitalisation from RTI
WS4* - cluster randomised controlled
trial Clinical and cost effectiveness of clinical
rule + parent information
Years 1
2
3
4
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WS3 – CPR study
• Research questions • Can baseline characteristics be used to
predict the need for hospitalisation in children <12 years presenting to primary care with acute cough?
• Do specific bacteria and/or viral microbes (or combinations of microbes) predict poor prognosis?
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WS3 – CPR study
• Design: prospective cohort (derivation and validation) study
• Eligibility: Children <12 years presenting to primary care with acute cough
• Independent variables• Baseline symptoms and signs + other
characteristics (e.g. deprivation)• Detailed microbiology and virology
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WS3 – CPR study
• Dependent variables• Primary – hospitalisation• Secondary - symptom duration, symptom
severity, antibiotic prescribing and reconsultations
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WS3 – CPR study
• Challenges• How to determine sample size• Logistics of recruiting a large cohort• Minimising (and/or adjusting for) spectrum
bias• Confounding by indication
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WS3 – CPR study
• Sample size methods1. Certainty with which strength of association
between individual predictors and outcome
2. Overall precision of the sensitivity and specificity of a validated rule
3. Ratio of candidate predictors to outcome events
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WS3 – CPR study
• Recruitment logistics• Collaboration• Simple data collection proforma• Web and paper based• Re-imbursement for clinician time
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DESCARTE pooled recruitment up to end of May 2009(Consent Form Data)
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Months of study
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Actual cumulative recruitment
WS3 – CPR study
• Spectrum bias• Difference in illness (e.g. aetiology) between
derivation and validation datasets• Can undermine validation• One potential solution is to anticipate which
parameters are most likely to change and• Measure them (e.g. microbiology)• Adjust analysis for them
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WS3 – CPR study
• Confounding by indication• Can potentially be reduced by
Derive and validate in the control arm of a RCT (unlikely to be ethical)
Assume that antibiotic prescribing is not associated with risk of outcome and exclude children prescribed antibiotics
Include all children, look for association between antibiotics and key predictors and model antibiotic effects
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Summary
• Albeit with some limitations, CPRs can be appropriately applied in the infection field. Limitations include• Spectrum bias• Confounding by indication (antibiotic use)
• Logistic challenges of recruiting large sample sizes• Collaboration• Use of technology to help manage data
• Funders want to support CPR research