The Landscape and Lexicon of Blinding in Randomized Trials

Medical Writings5 February 2002The Landscape and Lexicon of Blinding in Randomized TrialsKenneth F. Schulz, PhD, MBA, Iain Chalmers, DSc, and Douglas G. Altman, DScKenneth F. Schulz, PhD, MBADr. Schulz: Family Health International, Research Triangle Park, NC 27709Dr. Chalmers: United Kingdom Cochrane Centre, Oxford, United Kingdom OX2 7LGProfessor Altman: ICRF Medical Statistics Group, Centre for Statistics in Medicine, Institute of Health Sciences, Oxford, United Kingdom OX3 7LF, Iain Chalmers, DScDr. Schulz: Family Health International, Research Triangle Park, NC 27709Dr. Chalmers: United Kingdom Cochrane Centre, Oxford, United Kingdom OX2 7LGProfessor Altman: ICRF Medical Statistics Group, Centre for Statistics in Medicine, Institute of Health Sciences, Oxford, United Kingdom OX3 7LF, and Douglas G. Altman, DScDr. Schulz: Family Health International, Research Triangle Park, NC 27709Dr. Chalmers: United Kingdom Cochrane Centre, Oxford, United Kingdom OX2 7LGProfessor Altman: ICRF Medical Statistics Group, Centre for Statistics in Medicine, Institute of Health Sciences, Oxford, United Kingdom OX3 7LFAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-136-3-200202050-00022 SectionsAboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail Blinding in medical research possesses a rich history spanning a couple of centuries (1). Most researchers and readers grasp its meaning. Unfortunately, beyond that general understanding lies confusion. In addition to terms such as “single blind” and “double blind” meaning different things to different people, some steadfastly refuse to use the term “blinding” and insist instead on the term “masking.” Others confuse blinding with other methodologic precautions, such as concealment of allocation during the process of creating comparison groups. Still others consider that randomization is of little use unless accompanied by “double-blinding,” thus revealing that they have not understood that ...References1. Kaptchuk TJ. Intentional ignorance: a history of blind assessment and placebo controls in medicine. Bull Hist Med. 1998;72:389-433. [PMID: 9780448] CrossrefMedlineGoogle Scholar2. Lang T. Masking or blinding? An unscientific survey of mostly medical journal editors on the great debate. MedGenMed. 2000:E25. [PMID: 0011104471] Google Scholar3. Pocock SJ. Clinical Trials: A Practical Approach. Chichester, UK: Wiley; 1983. Google Scholar4. Meinert CL, Tonascia S. 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Altman, DScAffiliations: Dr. Schulz: Family Health International, Research Triangle Park, NC 27709Dr. Chalmers: United Kingdom Cochrane Centre, Oxford, United Kingdom OX2 7LGProfessor Altman: ICRF Medical Statistics Group, Centre for Statistics in Medicine, Institute of Health Sciences, Oxford, United Kingdom OX3 7LFAcknowledgment: The authors thank Dr. Ted J. Kaptchuk for his review of earlier drafts of this manuscript.Corresponding Author: Kenneth F. Schulz, PhD, MBA, Family Health International, Box 13950, Research Triangle Park, NC 27709.Current Author Addresses: Dr. Schulz: Family Health International, Box 13950, Research Triangle Park, NC 27709.Dr. Chalmers: UK Cochrane Centre, NHS Research and Development Programme, Summertown Pavilion, Middle Way, Oxford, United Kingdom OX2 7LG.Professor Altman: ICRF Medical Statistics Group and Centre for Statistics in Medicine, Institute of Health Sciences, Old Road, Headington, Oxford, United Kingdom OX3 7LF. 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