Making trials more efficient: a randomised study within a trial evaluating self-directed online versus phone call enrolment processes

Enrolment processes in randomised controlled trials can be resource intensive and often are not scalable beyond trial contexts. There is little comparative evidence on the effectiveness and efficiency of utilising digital tools to support trial enrolments. The aim of this Study Within A Trial (SWAT) was to evaluate the comparative effectiveness and efficiency of a self-directed online enrolment process compared with a phone call within the context of a hybrid effectiveness-implementation trial. Eligible trial participants completing a brief online expression of interest (EOI) and eligibility survey were individually randomised to schedule a baseline appointment via a researcher phone call or immediately via a co-designed self-directed online process. Those in the self-directed online group who did not self-schedule were followed up with a phone call. On an intention-to-treat basis, baseline scheduling rates and the proportion of eligible online EOIs ultimately randomised in the host trial were compared between enrolment conditions. Additionally, enrolment phone call duration (minutes) and call cost per participant randomised in the host trial were calculated. Of 325 EOIs who completed the online screening, 297 met the host trial eligibility criteria and were randomised to the self-directed online ( n = 146) or phone call ( n = 151) enrolment conditions. Participants in the self-directed online condition were more likely to schedule a baseline appointment (134/146, 91.8% vs. 126/151, 83.4%; p = 0.046), but the same proportion of participants were ultimately randomised in the host trial (114/146, 78.1% vs. 118/151, 78.1%; p > 0.999). The phone enrolment took longer (10.1 vs. 2.1 min) and cost more (AUD $8.23–9.76 vs. $1.70–2.02) than the self-directed online process per randomised host trial participant. In line with the host trial design, this SWAT provides ‘hybrid’ evidence to inform both trial enrolment processes and enrolments for the potential future real-world implementation of a men’s health intervention. Providing a self-directed online enrolment option could save resources without compromising participation rates, but a phone call option should remain available for inclusivity. Further research evaluating low resource alternatives to phone calls within and beyond trial contexts is warranted. This study is registered as SWAT#208 in the Northern Ireland Hub for Trials Methodology Research repository (registered 09/01/2023).