The many faces of recruitment in a randomized controlled trial

Thoughtful approaches to study recruitment are a critical step in designing and implementing randomized controlled trials. Delays and challenges in recruitment can be costly and can result in smaller than proposed sample sizes which have downstream effects, such as underpowered studies.

The current study evaluated recruitment methods (e.g., targeted mailings, brochures/flyers, social media) and their relationship to eligibility, randomization, participant characteristics and retention at end of a randomized controlled trial of physical activity adoption and maintenance among breast cancer survivors.

Screening data from 874 women was analyzed for recruitment method, study eligibility, randomization and retention through end of treatment. Costs per randomized participant were calculated by recruitment method. Baseline participant characteristics were compared across recruitment methods and between randomized and retained participants.

Rates of participant accrual from eligibility screening through randomization differed statistically significantly depending on recruitment method (p < .05). The highest randomization rates were obtained via targeted mailings (88.2%) and lowest via brochure/flyer (0.4%). Among the randomized sample, there were no differences in demographic characteristics between recruitment methods, however, there were differences within the targeted mailings category (registries vs. organizational recruitment). There were statistically significant differences in costs between recruitment methods (p < .001) with lowest (non-negligible) cost being targeted mailings.

The current RCT of breast cancer survivors successfully recruited and retained participants, highlighting the need to combine recruitment methods to achieve accrual goals. Recruitment methods differed substantially in their cost and their ability to attract individuals who would ultimately be randomized.