Clinical trials : journal of the Society for Clinical Trials
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With increasing emphasis on pragmatic trials, new randomized clinical trial designs are being proposed to enhance the "real world" nature of the data generated. We describe one such design, appropriate for unmasked pragmatic clinical trials in which the control arm receives usual care, called "Trials within Cohorts" that is increasingly used in various countries because of its efficiency in recruitment, advantages in reducing subject burden, and ability to better mimic real-world consent processes. ⋯ Trials within Cohorts is a promising new pragmatic randomized controlled trial design that is being increasingly used in various countries. Although the asymmetric consent procedures for the experimental versus control arm subjects can initially raise ethical concerns, it is ethically superior to previous post-randomization consent designs and can have important advantages over traditional trial designs.