Development of a complex intervention improved randomization and informed consent in a randomized controlled trial.

OBJECTIVE Multicenter randomized trials are required for pragmatic evaluations of health care interventions, but recruitment is difficult. Systematic reviews failed to identify robust strategies to improve recruitment. We developed and evaluated a complex intervention to increase levels of randomization and informed consent. STUDY DESIGN AND SETTING The ProtecT (Prostate testing for cancer and Treatment) trial compares radical surgery, radical conformal radiotherapy, and active monitoring for men aged 50-69 years with localized prostate cancer. The intervention was developed using qualitative research methods (content, thematic and conversation analysis). Rates of randomization and immediate acceptance of allocation were measured every 6 months to evaluate the impact of the intervention. RESULTS The complex intervention comprised reviews of centers falling below study targets, training programmes, documents and individually tailored feedback. Over 65% of eligible participants consented to randomization. Trial participants became increasingly well informed as immediate acceptance of allocation rose from 65% to 81% between 2001 and 2005. CONCLUSION This complex intervention resulted in high levels of randomization and informed consent in a difficult trial. The generic aspects of the intervention could be applied to other trials to maximize randomization and informed consent, and allow the mounting of trials previously considered too difficult.