Table 1 Appraisal of design options for exploratory trial in phase II
Experimental designs | Â | Â |
|---|---|---|
| Â | 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 | Â | Â |
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. |