The design and analysis of matched-pair cluster randomised trials

Abstract

Cluster randomised trials (CRTs) are studies in which groups (clusters) of individuals, such as a group of patients that see the same general practitioner (GP), are randomised to one of two (or more) treatment conditions that are being compared, rather than the individuals themselves. CRTs have certain design and analytical challenges not found in trials that randomise individuals. One design issue is related to the greater risk of imbalance of important prognostic factors between trial arms, especially when the number of clusters randomised is small. In order to avoid chance imbalance on important factors, a matched-pair design is often employed, where clusters are paired according to a nu..