Empirical assessment suggests that existing evidence could be used more fully in designing randomized controlled trials.

Background: Meta-analyses of randomized controlled trials (RCTs) provide the highest level of evidence regarding the effectiveness of interventions. Less is known about how they are used to inform the design and reporting of RCTs.

Methods: A sample of RCTs published in leading medical journals in 2007 was assessed to establish whether authors considered previous trials in the design of their trial.