Influence of preferences in intervention research: A scoping review

Introduction: Accounting for treatment preferences is beneficial in practice, it increases adherence to treatment and improves health outcomes. The randomized controlled trial (RCT) is considered the most robust in generating valid evidence on effectiveness, yet it ignores participants’ preferences for treatment. This scoping review addressed three questions: 1) How are treatment preferences conceptualized in intervention research? 2) To what extent do treatment preferences affect participants’ enrollment in trials, withdrawal from the study, adherence to treatment, and outcomes? And 3) What designs are used to account for treatment preferences in intervention evaluation research? Methods: The first five steps of the scoping review methodology framework were applied: 1) identifying the research questions; 2) searching the literature; 3) selecting articles; 4) charting data; and 5) summarizing findings. Results: Treatment preferences refer to choice treatment; they are shaped by participants’ beliefs and appraisal of the interventions. Evidence from reviews and primary studies indicated that offering participants the opportunity to choose and receive the preferred treatment enhances enrollment and reduces withdrawal in trials; however, the evidence regarding the influence of treatment preferences on adherence to treatment and improvement in outcomes is inconclusive. Designs that account for treatment preferences include: RCT, RCT with a comprehensive cohort, partially randomized preference trial, and two-stage partially randomized trial. Conclusion: The pattern of results may be attributed to the methods for assessing treatment preferences. A systematic method for assessing preferences is recommended.