Feasibility, effectiveness and costs of a decision support intervention for consultees and legal representatives of adults lacking capacity to consent (CONSULT): protocol for a randomised study within a trial

Background: Randomised trials play a vital role in underpinning evidence-based care. However, trials involving adults with impaired capacity to consent raise a number of ethical and methodological challenges, leading to the frequent exclusion of this group from trials. This includes challenges around involving family members as alternative ‘proxy’ decision-makers. Family members are often given little information about their role as a consultee or legal representative. Some family members find making a decision about trial participation difficult and may experience an emotional and decisional burden as a result. Families have reported a need for greater support and guidance when making such decisions, leading to the development of a decision aid (‘Making decisions about research for others’) for family members acting as consultee/legal representative. The decision aid now requires evaluation to determine its effectiveness in supporting families to make more informed decisions. Methods: This protocol describes a prospective, multi-centre, randomised-controlled Study Within a Trial (SWAT) to evaluate the effectiveness of the decision aid. The SWAT will initially be embedded in approximately five host trials. SWAT participants will be randomised in a 1:1 ratio to either the intervention (decision aid alongside standard information about the host trial provided to consultees/legal representatives) or control (standard information alone). The primary outcome is the quality of proxy consent decision, assessed by the Combined Scale for Proxy Informed Consent Decisions (CONCORD). The SWAT design is informed by previous qualitative research. Initial feasibility will be explored in one host trial, followed by the main SWAT. An embedded process evaluation and economic evaluation will enable the SWAT findings to be contextualised and identify factors likely to affect implementation. Discussion: This SWAT will generate the first evidence for recruitment interventions for trials involving adults lacking capacity to consent and add to knowledge about the use of decision support interventions in trial participation decisions. The SWAT will be embedded in a range of trials, and the heterogenous nature of the host trials, settings and populations involved will enable the intervention to be evaluated in a wide range of contexts. However, a pragmatic and flexible approach to conducting the SWAT is needed. Trial registration: The SWAT is registered as SWAT #159 with the Northern Ireland Hub for Trials Methodology Research SWAT repository (registered 09.08.2020). Each host trial will be registered on a clinical trials registry