Clinical trials conducted at clinical sites are limited to enrolling people who live nearby and are able to attend visits at clinics. Some types of clinical trials can be performed without clinical sites, which enables people to participate regardless of proximity to a clinical site or limitations that make visits difficult. Trials at clinical sites involve face-to-face relationships with in-person collection of informed consent, examinations, data, and specimens. In contrast, without clinical sites, informed consent and data are obtained online, limited examinations can be performed by telemedicine or visiting research nurses, biospecimens can be collected by visiting nurses or local laboratories, and treatments can be sent to homes or administered by nurses in participants' homes. Trials without clinical sites require internet access and must adapt to the lack of face-to-face interactions with study staff, with communication conducted by email, telephone, or video. Many trials cannot be performed entirely without clinical sites because they require examinations, tests, or treatments that must be given at a clinical site. However, some of the methods required for trials without sites, such as online data collection, follow-up visits by telemedicine or research nurses, and delivery of treatments to home, could reduce the need for visits to clinical sites and reduce the burden of participating in a clinical trial. When feasible, conducting clinical trials without clinical sites has the potential to expand participation and the generalizability of their results.
