Conducting a two-stage preference trial: utility and challenges

Treatment preferences reflect individuals' choice of therapy and influence their adherence to treatment and achievement of outcomes. The two-stage partially randomized clinical or preference trial (two-stage PRCT) is an appropriate design for examining the contribution of treatment preferences. It involves a two-stage process for assigning participants to treatments, which is useful to dismantle the effects of the treatments from those of treatment preferences. In this paper, we explain the role of treatment preferences in intervention evaluation research, describe the protocol for implementing the two-stage PRCT, and discuss issues in its application. The issues are encountered in the selection of treatments, assignment of participants and assessment of treatment preferences. Lastly, we propose ways to address the issues.