How to design and set up a clinical trial part 1: the research question

Clinical trials involve observations or interventions undertaken with human participants (usually patients) to provide information concerning specific questions about the safety or effectiveness of treatment. Laboratory and animal studies might provide some initial indications in these areas, however, they almost always lack clinical validity and can rarely replace clinical data obtained in a scientific manner.¹ The evidence derived from clinical trials may be used together with clinical judgement and patients' values as part of an evidence-based approach to care (Figure 1).

There are various study designs (which can be broadly classified into quantitative and qualitative approaches), but the most appropriate design depends upon the research question to be answered. Current conventional wisdom is that a quantitative randomized controlled trial (RCT), which attempts to reduce the potential influences of both the patient and researcher, is the best design for interventional studies in both medicine and dentistry. However, there may be practical, ethical or cost considerations that prevent the use of this design. The study of human motivations and behaviour may require a qualitative approach but, for the purposes of this article, we will mainly focus on the design and setting up of a clinical trial using a quantitative approach.