A randomized comparison of recruitment messages for a weight loss clinical trial targeting men working in trade and labor occupations

Background: Engaging diverse populations in clinical trials is vital to research. This study evaluated the effects of varying recruitment messages for a clinical trial. Methods: The messages were evaluated in a randomly assigned, factorial design that tested enhanced trust (vs. standard) and participant endorsement (vs. standard) messaging. Four postcards were developed and randomly assigned to 4000 potential participants' addresses. Except for the messages of interest, the cards were identical, and participants were directed to four identical study websites and screening forms. Outcomes include unique website visits, visit conversion rate, screening forms completed, and participants randomized into the parent study. Results: Study websites received 74 visits (range by message type 9 to 34). There was no significant difference by message type (p = 0.79). Online screening forms were completed by 15 participants (range by message type 0-6), representing a conversion rate of 20.3% of website visits. Seven participants were randomized into the study in response to the postcards (range by message type 0 to 3; 46.7% of screenings). Overall, 0.2% of individuals who received a postcard were randomized into the study. Conclusion: Despite developing recruitment messages with participant input, the enhanced messages did not yield a greater response than standard messages. However, this method of evaluating recruitment messages shows promise.