Allocation Concealment in Randomised Controlled Trials:Could do Better

Separating the act of randomisation from the person recruiting a trial participant is the keystone for a robust randomised controlled trial. Much methodological research has demonstrated that randomisation could be subverted by researchers or clinicians if the possibility exists. Consequently, for a RCT to be robust methods must be used to ensure that allocation subversion is difficult or impossible. However, in a sample of 79 trials published in major medical journals in June-August 2015 a large proportion (19%) used suboptimal allocation concealment, which undermines their rigour. Journals should specify that in future, trials will not be published if they used sub-optimal allocation methods. Furthermore, trials that use blocked randomisation should statistically test whether or not there is a relationship between block position and outcome.