Masking

AbstractBlinding, along with allocation concealment and randomization, is a primary procedure used to control biases in clinical trials. Blinding may refer to both (1) the procedures that are used to keep persons associated with the trial (participants, investigators, and such) ignorant of the treatments to which the individual participants have been assigned and (2) the results of such efforts. Different individuals associated with a clinical trial bring different potential biases to the trial if they are not blinded. Blinding and allocation concealment both help to reduce biases in clinical trials, but allocation concealment seems even more important than blinding. Blinding may take place at varying levels from no one blinded (“open‐label”), to single‐blind, to double‐ and triple‐blind. The International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines and the Consolidated Standards of Reporting Clinical Trials guidelines encourage the reporting of details of blinding procedures used in clinical trials and the results they attained, including information about who may have been unblinded during the trials and what biases that may have generated therefrom.