Supporting recruitment into complex trials: An embedded qualitative process evaluation in the RADICAL trial of radiofrequency denervation for chronic low back pain.

Aims: A qualitative process evaluation was embedded into the pilot phase of the RADICAL randomised controlled trial of radiofrequency denervation for chronic and moderate-severe low back pain. The aim was to rapidly understand recruitment processes and inform development of strategies to overcome recruitment challenges. Methods: Audio recording of recruitment consultations between recruiting staff and potential patient participants, and interviews with patients who had consented to participate in the RADICAL trial. We used rapid thematic analysis to identify what information was provided, understanding of trial processes and potential challenges to recruitment. Results: Recruitment staff needed more support to clearly and effectively explain trial participation. Specific challenges included communicating trial procedures, explaining treatment equipoise and randomisation, and navigating the complex recruitment pathway. These findings led to the development of support materials for recruiters, including a process diagram and targeted training sessions to optimise information provision and informed consent. Conclusion: Embedding qualitative process evaluations within an RCT pilot can generate rapid insights into communication challenges and recruitment barriers. These insights can inform the development of practical support materials and process refinements to enhance recruitment, potentially strengthening trial viability.