Influence of trial design, heterogeneity and regulatory environment on the results of clinical trials: An appraisal in the context of recent trials on acute stroke intervention

The outcome of randomized controlled trials can vary depending on the eligibility criteria of the patients entering into the trial, as well as the heterogeneity of the eligible population and/or the interventions. If the subject population and/or interventions are heterogeneous, the final outcome of the trial depends on the degree of concordance of effects of the subgroups of interventions on the subgroups of the subject population. The considerations that go into the calculation of sample size and determination of the study stopping rules also would affect the nature of the outcome of the study. In this paper we try to examine these phenomena with respect to the recent trials on endovascular therapy in acute ischemic stroke.