Assessment of blinding in clinical trials

Heejung Bang, Liyun Ni, Clarence E. Davis

Research output: Contribution to journalArticlepeer-review

288 Scopus citations


Success of blinding is a fundamental issue in many clinical trials. The validity of a trial may be questioned if this important assumption is violated. Although thousands of ostensibly double-blind trials are conducted annually and investigators acknowledge the importance of blinding, attempts to measure the effectiveness of blinding are rarely discussed. Several published papers proposed ways to evaluate the success of blinding, but none of the methods are commonly used or regarded as standard. This paper investigates a new approach to assess the success of blinding in clinical trials. The blinding index proposed is scaled to an interval of -1 to 1, 1 being complete lack of blinding, 0 being consistent with perfect blinding and -1 indicating opposite guessing which may be related to unblinding. It has the ability to detect a relatively low degree of blinding, response bias and different behaviors in two arms. The proposed method is applied to a clinical trial of cholesterol-lowering medication in a group of elderly people.

Original languageEnglish (US)
Pages (from-to)143-156
Number of pages14
JournalControlled Clinical Trials
Issue number2
StatePublished - Apr 2004
Externally publishedYes


  • Blinding
  • Blinding index
  • Clinical trial
  • Masking
  • Multinomial test

ASJC Scopus subject areas

  • Pharmacology


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