Stephen J. Page, Andrew C. Persch; Recruitment, Retention, and Blinding in Clinical Trials. Am J Occup Ther 2013;67(2):154–161. https://doi.org/10.5014/ajot.2013.006197
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The recruitment and retention of participants and the blinding of participants, health care providers, and data collectors present challenges for clinical trial investigators. This article reviews challenges and alternative strategies associated with these three important clinical trial activities. Common recruiting pitfalls, including low sample size, unfriendly study designs, suboptimal testing locations, and untimely recruitment are discussed together with strategies for overcoming these barriers. The use of active controls, technology-supported visit reminders, and up-front scheduling is recommended to prevent attrition and maximize retention of participants. Blinding is conceptualized as the process of concealing research design elements from key players in the research process. Strategies for blinding participants, health care providers, and data collectors are suggested.
Participants should be blinded to group assignment to control for the psychological effects associated with knowing group assignment. Participant knowledge of group assignment may bias the study in terms of altered attitudes, compliance, cooperation, and attendance (Pocock, 1983).
Health care providers are the people administering the intervention to participants or are professionals otherwise involved in the care of participants during the trial. Blinding of health care providers is especially important when knowledge of group assignment may affect normal care treatment decisions, cause a provider to monitor changes more closely, or result in increased excitement or enthusiasm (Pocock, 1983).
Data collectors may administer outcome assessments, score assessments, analyze the data, and manage databases. Blinding of the data collector to group assignment is necessary to ensure objectivity and avoid the risk that assessors will record more favorable responses when treatment status is known or may assume that improved performance is evidence of treatment status (Pocock, 1983). Blinding of data collectors is also important in behavioral trials because of the influence of clinical judgment on outcome assessments.
Development and implementation of the recruiting plan start before the study begins.
Successful recruiting plans incorporate both active and passive recruiting strategies.
Participant retention can be maximized through the use of designs with active controls, technology-supported visit reminders, and up-front scheduling.
Participants, health care providers, and data collectors should be blinded when possible.
Concealing design elements from key players helps minimize threats of bias.
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