Methods and Applications of Statistics in Clinical Trials, Volume 1: Concepts, Principles, Trials, and Designs

Chapter 64

Preference Trials

Marion K. Campbell and Davic J. Torgerson

64.1 Introduction

When evaluating the effectiveness of interventions in health-care, it is now widely accepted that the randomized controlled trial is the gold standard design to adopt (1,2). When randomization is adopted, this results in a number of benefits; for example, the groups generated should only differ by chance in baseline prognostic variables (i.e., bias is minimized), the potential for attribution is maximized, and the results can be analyzed using standard statistical testing.

Acceptance of the standard randomized trial, however, requires that patients recruited to the trial be prepared to accept any of the interventions under study. Some participants may have explicit preferences for one of the treatments under evaluation, which may affect their willingness to participate in a standard randomized controlled trial, and they may refuse to be randomized [3]. If the proportion of eligible participants who refuse randomization is significant, this jeopardizes the generalizability of the trial results [4]. However, if the preferred treatment is only available within the context of a randomized trial (e.g., a novel treatment), many people may consent to take part hoping to get access to the new treatment. This consent hoping to be allocated to only one treatment can have significant consequences for the trial. If, for example, 50% of those being recruited to a trial of A versus B want intervention A, ...