Randomized controlled trials
There are three main questions in health care: ‘what is going on?’, ‘why?’ and ‘what do we do about it?’. ‘What is going on?’ forms the basis for clinical assessment including history taking, examination, and diagnosis. The question ‘why?’ underlies all aetiological research from laboratory science to epidemiology. The cross-sectional, case–control and cohort methodologies discussed in other chapters in this book provide the methodology for addressing ‘why?’ questions. However, just as medicine is more than diagnosis it also covers treatment, medical research is more than aetiology: it also necessarily extends to the evaluation of interventions. Aetiological research which cannot be translated into health benefits through new or improved interventions is at best sterile and at worse selfindulgent, begging another important question: ‘so what?’. Flawed evaluations of interventions can be even more problematic since these may harm rather than help. Intervention studies (of which randomized controlled trials (RCTs) are the most important type, on the basis of quality of evidence available from them) take aetiological insights into action and provide the best evidence upon which to found clinical practice. In this chapter we will consider some of the more important factors in the design, conduct, analysis, and interpretation of RCTs.