Blinding

Explanation

Emergency unblinding reveals the assigned intervention of a trial participant, typically when experiencing potential harm of the intervention. It is important that emergency unblinding procedures are constrained to a single participant, and that unblinding of additional participants is avoided (Item 24b). In some cases (e.g., minor, reversible harms), stopping the assigned intervention, and then cautiously re-introducing it, can avoid both unblinding and further harm.

Reviews of two samples of 108 and 292 trial protocols from 2016 found that 81% and 90% addressed the conditions when unblinding was permissible.(9, 10)

A clear protocol description of the circumstances and procedures for emergency unblinding helps to prevent unnecessary unblinding, facilitates implementation by trial personnel when indicated, and enables evaluation of the appropriateness of the planned procedures.

Summary of key elements to address

For blinded trials:

• Circumstances under which unblinding is permissible during the trial (e.g., to reduce immediate risk for a participant)

• Procedure for revealing a participant’s allocated intervention during the trial