Introduction to Cluster Randomized Trials

Abstract

As healthcare professionals, we frequently read studies evaluating new interventions. Traditionally, most of these studies are individually randomized controlled trials, in which individual patients are randomly assigned to a new treatment. However, we may also encounter a different methodological design: the cluster-randomized controlled trial (cRCT). To critically appraise these studies, we need to understand what a cRCT is, why it is used, and whether the appropriate methodology was applied. The purpose of this article is to provide the tools to assess the quality and validity of these trials.