Pilot and feasibility studies for pragmatic trials have unique considerations and areas of uncertainty

Feasibility studies are increasingly being used to support the development of, and investigate uncertainties around, future large-scale trials. The future trial can be designed with either a pragmatic or explanatory mindset. Whereas pragmatic trials aim to inform the choice between different care options and thus, are designed to resemble conditions outside of a clinical trial environment, explanatory trials examine the benefit of a treatment under more controlled conditions. There is existing guidance for designing feasibility studies, but none that explicitly considers the goals of pragmatic designs. We aimed to identify unique areas of uncertainty that are relevant to planning a pragmatic trial.We identified ten relevant domains, partly based on the pragmatic-explanatory continuum indicator summary-2 (PRECIS-2) framework, and describe potential questions of uncertainty within each: intervention development, research ethics, participant identification and eligibility, recruitment of individuals, setting, organization, flexibility of delivery, flexibility of adherence, follow-up, and importance of primary outcome to patients and decision-makers. We present examples to illustrate how uncertainty in these domains might be addressed within a feasibility study.Researchers planning a feasibility study in advance of a pragmatic trial should consider feasibility objectives specifically relevant to areas of uncertainty for pragmatic trials.