The use of a run-in to enhance compliance

With a run-in, potential subjects are given practice with all or part of the study protocol prior to randomization. The purpose is to exclude poor compliers from the trial and randomize only proven, good compliers. The feasibility of a run-in and the net benefit derived from that strategy depend upon the difficulty of the protocol; the availability of compliance aids during the trial; and the impact of the chosen common practices for all subjects during the run-in on the post-randomization event rates of the groups and the post-randomization blinding of study subjects to their treatment assignments. Two detailed examples of the use of a run-in are presented along with six general recommendations to guide the use of a run-in.