Recruitment of individuals into a type 2 diabetes prevention program: the relative effectiveness and cost of different recruitment strategies used for the randomised controlled trial testing an Australian Lifestyle Change Program (AUS2PREVENT)

BACKGROUND: Governments worldwide consider randomised controlled trials (RCTs) as the accepted gold standard design to evaluate healthcare interventions. However, enrolling participants into RCTs can be challenging, with recruitment processes serving as a crucial determinant of any clinical trial or program's success. This study aimed to characterise the relative effectiveness and cost of different strategies used to recruit individuals into a randomised controlled trial of an Australian Lifestyle Change Program (AUS2PREVENT) to prevent or delay type 2 diabetes in South Australia. METHODS: Targeted recruitment over a 12-month period through General Practitioner (GP) clinics was the primary strategy used to recruit individuals at risk of, or with prediabetes. After protocol amendments, around 25,000 individuals were identified as having prediabetes and being potentially eligible for the trial from 279 GP clinics across metropolitan Adelaide. Additional channels that were used to recruit high-risk individuals included radio, online media (e.g. Facebook, Instagram, webpages), email distribution lists, and member-oriented magazines/ newsletters associated with the supporting health and community organisations. RESULTS: Of the 1393 expressions of interest, 587 individuals completed the pre-screening survey and reported the referral channel. Radio, email, and online media generated the greatest number of individuals expressing interest in the trial (284 vs 151 vs 91, respectively) and accounted for the final 67 individuals who were enrolled and randomised. Only 4 individuals reported being referred by their GP. Promotion through radio, GP clinics, and online media was the costliest strategy. CONCLUSIONS: Although feasibility precision targets were achieved, continuing to recruit for a fully powered main trial to demonstrate the effectiveness of the AUS2PREVENT Program under current timelines and resources was not viable, and underscores the need for major design or strategy changes. Effective, timely, and cost-efficient recruitment for preventive health trials requires an adaptive, multi-channel strategy tailored to high-risk populations, supported by strong coordination among health organisations, trust-building efforts, and substantial marketing resources. TRIAL REGISTRATION: The trial is registered on the Australian New Zealand Clinical Trials Registry (ANZCTR), Universal Trial Number U1111-1220-5636.