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Table 1 Groups reported to be blinded in a double-blind trial. Data are from 2 studies of () 130a and () 91b physicians and from 2 studies of () 83c and () 194d published randomized trials described as “double-blinded.” Combinations of 3 or more groups were often included in the definition of double-blind

From: Who knew? The misleading specificity of “double-blind” and what to do about it

  1. aData are from Table 5 in Haahr MT, Hróbjartsson A. Who is blinded in randomized clinical trials? A study of 200 trials and a survey of authors. Clin Trials 2006;3(4):360-5
  2. bData are from the table in Devereaux PJ, Manns BJ, Ghali WA, et al. Physician interpretations and textbook definitions of blinding terminology in randomized controlled trials. JAMA. 2001;285:2000-3. Of 17 unique group combinations, 9 are shown. Presumably, the remaining 8 combinations included “other groups” thought to be blinded (e.g., laboratory technicians, pharmacists)
  3. cIn this study of 83 “double-blind” trials, 49% (41) did not indicate which groups were blinded. Data are from Table 2 in Montori VM, Bhandari M, Devereaux PJ, et al. In the dark: the reporting of blinding status in randomized controlled trials. J Clin Epidemiol 2002;55:787-790
  4. dData are from Table 1 in Viergever RF, Ghersi D. Information on blinding in registered records of clinical trials. Trials 2012 Nov 15;13:210