Blinding in Clinical Trials

Unblinding is the process by which the allocation code is broken so that the appropriate persons e.g. investigator, clinical staff, participants, and/or the trial statistician become aware of the intervention for a participant in a trial.

Unblinding must be undertaken by a pre-determined process to ensure that participants are not unblinded unnecessarily and the study results are not compromised. Equally, unblinding should occur in a responsive manner when it is clinically indicated.

Unblinding is required:

• To make clinical treatment decisions or when an unexpected serious adverse event occurs and the intervention must be made known. This is called emergency unblinding (to protect the participant). Unblinding should only occur for that participant and not the entire study.
  
• During an unmasked analysis in accordance with the study analysis plan (e.g. a planned interim analysis).
  
• At the request of the Data Safety Monitoring Board.
  
• At the conclusion of the study to determine the effect of the intervention.

It may be done by: