Effects of Participant Preferences in Unblinded Randomized Controlled Trials

Abstract

Little research has deliberately investigated the effects of participant preferences for treatment condition in unblinded randomized controlled trials. We designed a study with a non-patient sample comparing a randomized arm to a preference arm of the same trial to investigate: (1) whether having a choice to select one's preference affects feelings about participation, belief in treatment effectiveness, treatment contamination, intervention adherence and engagement, and trial attrition; and (2) the interaction of preferences and treatment assignment on these variables. Contamination and attrition were rare and excluded from analyses. There was no effect of choice. Participants mismatched to preference felt less positive about their experience, but this did not affect belief in treatment, adherence, or engagement. Stronger effects may occur for patient populations.

Do Participants’ Preferences for Mode of Delivery (Text, Video, or Both) Influence the Effectiveness of a Web-Based Physical Activity Intervention?

“…The acceptability, usability, and effectiveness of the physical activity intervention was not significantly different for participants matched or mismatched to their preferred intervention delivery mode (video based, text based, or combination). This finding is in line with other studies that have examined preference effects for other types of interventions within different populations [18-20,48]. Only in their study on human papillomavirus testing did McCaffery et al [30] find effects on quality of life based on preferences for different interventions.…”

“…Though acceptability of the advice and website usability were not influenced by delivery mode preferences in this study, others have seen an impact of participant satisfaction levels [20]. Therefore, in line with Foley et al [49], we recommend offering participants a delivery mode choice if possible, as it will not harm intervention effectiveness, and might also increase participant satisfaction levels.…”

“…Participants may also drop out of a trial after being assigned to the nonpreferred mode, or may enter and remain in the study but not adhere to or be engaged in the treatment [20]. As such, randomly assigning participants to nonpreferred delivery modes may reduce their participation, follow-up, and satisfaction, and may thus lead to poor outcomes [21].…”

“…In a comparison of interventions delivered by print or telephone, Lewis et al [18] found that being in the preferred group did not influence physical activity levels. A few medical studies have also examined the influence of preferences on treatment outcomes, but with inconclusive results: some studies found better effects on satisfaction [20] and effectiveness [30] when participants were allocated to the preferred group and others not [19]. Overall, there is little evidence that preference effects significantly compromise internal validity [19], but this conclusion rests on a small number of studies.…”

Understanding Patient Values and the Manifestations in Clinical Research with Traditional Chinese Medicine—With Practical Suggestions for Trial Design and Implementation

“…The phenomenon has been evidenced by the findings of a systematic review and patient level meta-analysis of 17 musculoskeletal trials, which found patients randomized to their preferred treatment did better than participants who were indifferent to allocation or those who received unopted treatment [14]. However, other studies [8, 15] came to contradictory results and found insufficient empirical evidence in proof of consistent effect of preference on outcomes.…”