Masking Study Participants

Lea Drye ()
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Lea Drye: Blue Cross Blue Shield Association, Office of Clinical Affairs

Chapter 44 in Principles and Practice of Clinical Trials, 2022, pp 815-821 from Springer

Abstract: Abstract Masking or blinding in clinical trials refers to the process of keeping the identity of the assigned treatment hidden from specific groups of individuals such as participants, study staff, or outcome assessors. The purpose of masking is to minimize conscious and unconscious bias in the conduct and interpretation of a trial. Masking participants in clinical trials is a key methodological procedure since patient expectations can introduce bias directly through how a participant reports patient-reported outcomes but also indirectly through his or her willingness to participate in and adhere to study activities. The complexity of operational aspects of masking participants is often underestimated. Masking is facilitated by placebos, dummies, sham devices, or sham procedures/surgeries. The success of masking depends on how closely the placebo or sham matches the active treatment. Creation of a completely identical placebo is generally possible only when active drug and matching placebo are provided by the manufacturer. Masking of participants becomes more complicated if there are more than two experimental treatment groups, an active control, if treatments are taken at different intervals or via different routes, or if sham devices or procedures are required. Trials in which participants are masked should have procedures in place to unmask. Most unmasking is routine unmasking in which investigators communicate treatment assignment with participants after treatment and follow-up are complete. In addition to this routine unmasking, masked trials should have procedures to immediately unmask at any hour of the day in the event of an emergency.

Keywords: Blind; Mask; Single mask; Double mask; Unmask; Placebo; Sham (search for similar items in EconPapers)
Date: 2022
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DOI: 10.1007/978-3-319-52636-2_216

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