What is an equivalence trial?
Medical science is preoccupied with improving existing treatments, so most clinical trials are designed to show that a new treatment is better than placebo or better than standard therapy. And rightly so, otherwise the textbooks would still cite "leeches" and "eye of newt" as time-honoured therapies. But when proven therapies already exist and a new treatment is unlikely to have superior efficacy (but may be safer, easier to use or less expensive), we sometimes want to know whether the new treatment is "as good as" standard therapy. Equivalence trials are used to prove that two treatments work equally well, in contrast to traditional "superiority trials," which set out to show that one treatment is better than another.