View
216
Download
0
Category
Preview:
Citation preview
Introduce explanatory and pragmatic designs
The concept of a continuum rather than dichotomy
Use of the PRECIS wheel in BLISTER
Clinical implications of internal versus external validity
Conducted under “ideal” conditions Highly selected and homogeneous participants Usually tertiary care Good compliance Likely to remain in study Only one medical condition Strict dosing schedules Monitored closely To “explain” if a treatment works - efficacy
Treatment already known to work, but can it work in real world clinical practice? - effectiveness
Wider group of participants – co morbidity, less compliant
Maybe primary care setting
Flexible dosing, switching and rescue therapy compatible with daily practice – “policy” of a treatment pathway rather than one drug
Cost effectiveness key
Explanatory Pragmatic
Homogenous patients
Tightly defined intervention
Clearly defined control group – often placebo
Objective/surrogate outcomes
Real life patients
Flexible intervention with changes
Active comparator
Clinically important outcomes
Still have to fiercely minimise bias1.Selection - Randomisation and allocation
concealment2.Performance – similar conditions both
groups3.Detection bias – blinded outcome4.Attrition bias – collecting data on dropout
and intention to treat analysis
Is it explanatory or pragmatic? –
X wrong question
To what extent is it explanatory or pragmatic? –
√ right question
Thorpe KE et al: A pragmatic–explanatory continuum indicator summary (PRECIS): a tool to help trial designers. Journal of Clinical Epidemiology 2009, 62:464-475.
The Pragmatic-Explanatory Continuum Indicator Summary
Typically used as a tool when designing study
Requires a judgement on key aspects of trial design
Illustrated by a PRECIS wheel
PRECIS summary of a randomized trial of low-dose aspirin for the prevention and treatment of pre-eclampsia (Collaborative Low dose Aspirin Study in Pregnancy [CLASP])
PRECIS summary of a randomized trial of low-dose aspirin for the prevention of pre-eclampsia in women at high risk
Sent to six TMG members
Two pemphigoid experts
One clinician interested in clinical trials
Two trial statisticians
Eligibility Criteria
Flexibility of theExperimental Intervention
PrimaryAnalysis
PractitionerAdherence
ParticipantCompliance
Outcomes
Follow-upIntensity
PractitionerExpertise(Comparison)
Flexibility of theComparisonIntervention
PractitionerExpertise(Experimental)
Recommended