Measuring the success of blinding in placebo-controlled trials: Should we be so quick to dismiss it?

Published:February 28, 2021DOI:


      • What's new
      • Blinding in clinical trials has the potential to reduce bias.
      • There is a live yet underreported debate about the value of measuring blinding success.
      • Interpreting the success of blinding can be problematic and potentially misleading.
      • However, failure to report the success of blinding, if it is measured, seems like willful withholding of information that is at least potentially useful.
      • We suggest a middle road whereby the success of blinding be measured (where feasible) and interpreted with caution.


      ‘Blinding’ involves concealing knowledge of which trial participants received the interventions from participants themselves and other trial personnel throughout the trial. Blinding reduces bias arising from the beliefs and expectations of these groups. It is agreed that where possible, blinding should be attempted, for example by ensuring that experimental and control treatments look the same. However, there is a debate about if we should measure whether blinding has been successful, this manuscript will discuss this controversy, including the benefits and risks of measuring blinding within the randomised controlled trial.


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