Conducting a two-stage preference trial: Utility and challenges Souraya Sidani a, *, Mary Fox b , Dana Epstein c a School of Nursing, Ryerson University, Toronto, ON, Canada b School of Nursing, York University, Toronto, ON, Canada c Phoenix Veterans Affairs Health Care System Phoenix, AZ, U.S.A What is already known?  Participants’ preferences for treatment influence enroll- ment in intervention research, adherence to treatment, and outcomes.  Accounting for preferences in treatment allocation, an essential element of patient-centered care, improves treatment adherence, satisfaction and outcomes.  The two-stage preference trial is a research design used to examine the unique contribution of the intervention and of preferences. What this paper adds?  The protocol for implementing a two-stage preference trial is described.  Issues in the conduct of the two-stage preference trial are discussed.  Strategies to address the issues are proposed. 1. Introduction Preferences for treatment represent individuals’ choice of treatment (Stalmeier et al., 2007), that is, the treatment they desire to prevent illness, promote health or manage a presenting health problem. Treatment preferences are of clinical importance: they are a core element of patient- centered care defined as care that is sensitive and responsive to the person’s needs and preferences (Bokhour et al., 2009). Patient-centered care involves: providing International Journal of Nursing Studies 52 (2015) 1017–1024 A R T I C L E I N F O Article history: Received 24 September 2014 Received in revised form 25 January 2015 Accepted 6 February 2015 Keywords: Assignment to treatment Assessment of preferences Design Intervention research Methodology Preference trials Treatment selection Two-stage partially randomized trial A B S T R A C T 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. ß 2015 Elsevier Ltd. All rights reserved. * Correspondence to: Canada Research Chair Health Intervention Design and Evaluation School of Nursing, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, USA. Tel.: +1 416 979 5000x2572. E-mail addresses: ssidani@ryerson.ca (S. Sidani), mfox@yorku.ca (M. Fox), Dana.Epstein@va.gov (D. Epstein). Contents lists available at ScienceDirect International Journal of Nursing Studies journal homepage: www.elsevier.com/ijns http://dx.doi.org/10.1016/j.ijnurstu.2015.02.006 0020-7489/ß 2015 Elsevier Ltd. All rights reserved.