Are claims of equivalency in digestive diseases trials supported by the evidence?

Traditionally, randomized controlled trials (RCTs) have attempted to show the superiority of one intervention over another. However, when effective treatment already exists, it is sometimes more useful to prove that an intervention is equivalent, or at least not inferior, to the standard of care. Our aim was to determine whether claims of equivalency in digestive diseases trials are supported by the evidence.

Medline was searched for RCTs published between 1989 and 2002 using the MeSH headings "exp therapeutic equivalency" and "exp digestive diseases" and the text words "equivalence," "equal," "equals," or "equivalent," yielding 902 articles. Of these, 73 articles met the inclusion criteria. These articles were evaluated using previously published criteria for equivalency.

Of the included articles, 33% stated an a priori research aim of equivalency, 92% reported differences of <20% between "equal" interventions, 34% set an equivalency boundary and tested it appropriately, and 19% performed a sample size calculation for equivalency. Overall, 12% of the reviewed articles met all 5 criteria. Fifty-two percent of our sample inappropriately used a failed superiority test (i.e., a P value > 0.05) as statistical "proof" of equivalency. Nonsurgical trials and those published between 1996 and 2002 were more likely to meet criteria than were surgical trials (P = 0.07) or trials published before 1996 (P = 0.003).

Claims of equivalency between interventions in digestive diseases trials tend to be poorly supported by the evidence. Erroneous claims of equivalency are potentially dangerous and may lead to substandard patient care.