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Table 1 Appraisal of design options for exploratory trial in phase II

From: Study protocol: delayed intervention randomised controlled trial within the Medical Research Council (MRC) Framework to assess the effectiveness of a new palliative care service

Experimental designs   
  Pros Cons
Traditional randomised controlled trial Gold standard way to understand a difference between intervention and control Concerns regarding recruitment, patients/staff may not be willing to take part if some patients do not get intervention, some staff had ethical concerns
Cluster randomisation Reduce problem of disappointment of no service and contamination Need extremely large sample and number of clusters, analysis required at level of cluster
Patient preference randomisation Makes explicit problem of patients who have strong preference for one type of service Difficult for patients to have a preference when they know little about service, large sample size needed, potential for staff or others to advise patients to have a particular preference
Delayed intervention randomised trial All patients will eventually receive service, uses a gold standard methodology, it is common in this condition for patients to wait 3 months for appointments, longer survival means patients likely to actually receive service Some staff not happy for patients to wait 3 months, effect of service must be apparent before 3 months (i.e. before control group receive intervention)
Quasi-experimental designs   
Geographical comparison No problems of randomisation, potential to increase sample size by study in an area where no service Biases involved in variations in service provision between areas
Historical controls No problems of randomisation Biases in data collection and potentially in sample selection
Matched controls No problems of randomisation Biases in patient selection, difficulty of matching
Observational study No problems of randomisation No comparison group, only comparison with how patients were at referral, problems of regression to the mean, interviews and inclusion in study may have effect in itself.