[Noninferiority and equivalence randomized trials: lessons and reservations--secondary publication]

A noninferiority trial seeks to determine, whether a new intervention is not inferior to a reference intervention within a prespecified noninferiority interval (-Delta to 0) for the primary outcome. An equivalence trial aims to determine whether two interventions have a similar effect within a prespecified interval (-Delta to +Delta). These trials are controversial and difficult to grasp and very often poorly reported and conducted. Any claims regarding efficacy of new treatments, based on these trials, should be interpreted with caution, and it should be noted that Delta is often far too large to be clinically meaningful.