How to … do a randomized controlled trial

In this section of the series on orthodontic research we intend to give a brief outline of how to carry out a randomized controlled trial (RCT). The RCT is one of the most simple and powerful research tools in which people are allocated at random to receive one of several clinical interventions. We hope that this will not only provide information to anyone who is aiming to carry out research of this type, but also help in the interpretation of RCTs that have been published. Before we consider the mechanics of how to carry out an RCT we should consider the advantages of this type of research over other study methods. These are: • The RCT is prospective. As a result, the subjects and the data are under some control by the investigator. • The treatment or intervention is randomly allocated. Therefore, the perceptions of the investigator on the value of a particular treatment should not influence treatment allocation that could bias the results. • The study is planned before the data is collected. This is the important distinction between the RCT and the retrospective investigation, and this results in a mini-mization of bias that is inherent in the retrospective study. We hope that this simple guide will stimulate efforts to carry out randomized trials of some of our treatment methods. As with most of the ‘How to do ’ papers in this series, the ideas and concepts are a simple interpretation of the work of other authors. We have decided to use the CONSORT guideline