1 Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet2 Department of Pharmacology Pharmacotherapy, Faculty of Pharmaceutical Sciences, Københavns Universitet3 unknown4 Department of Pharmacology Pharmacotherapy, Faculty of Pharmaceutical Sciences, Københavns Universitet
Blinding, or "masking," is a crucial method for reducing bias in randomized clinical trials. In this paper, we review important methodological aspects of blinding, emphasizing terminology, reporting, bias mechanisms, empirical evidence, and the risk of unblinding. Theoretical considerations and empirical analyses support the blinding of patients, health-care providers, and outcome assessors as to the trial intervention to which patients have been allocated. We encourage extensive pretrial testing of blinding procedures and explicit reporting of who was in the blinded condition and the methods used to ensure blinding.
Clinical Pharmacology and Therapeutics, 2011, Vol 90, Issue 5, p. 732-6