Article type
Year
Abstract
Background:
Despite evidence that study personnel can and sometimes do tamper with envelopes, thus jeopardizing randomization, some clinical trials authorities, including the Cochrane Collaboration, maintain that envelopes adequately conceal allocation. Given the apparently conflicting evidence and recommendations, we explored the views of clinical trialists regarding the issue.
Objectives:
To evaluate clinical trialists’ views regarding the merits of using central randomization versus envelopes to conceal allocation in randomized controlled trials, and to test whether examples of apparent failure of envelopes could influence these views.
Methods:
A web-based survey administered to a random sample (n = 1926) of corresponding authors of randomized controlled trials published in one of 119 Core Clinical Journals between 1 January 2011 and 31 December 2012.
Results:
Four-hundred and ninety (490) participants completed the survey (25.4% response rate). Initially, 299 participants (61.0%) preferred using central randomization over envelopes to conceal allocation; nevertheless, 316 (64.5%) participants expressed views that envelopes are an adequate method to conceal allocation. After participants were shown examples that suggested envelopes’ vulnerability to manipulation, significantly more participants (69.0%) preferred central randomization (P value < 0.001), and significantly fewer participants (44.9%) expressed views that envelopes are an adequate method to conceal allocation (P value < 0.001).
Conclusions:
Although most trialists prefer central randomization to conceal allocation, most also considered envelopes an adequate concealment method, and a substantial minority continued in this view after viewing examples of the apparent vulnerability of envelopes to manipulation. Thus, the dangers of using envelopes and the desirability of consistent use of central randomization are underappreciated by clinical trialists, but empirical demonstration of envelopes' failure can influence trialists' views. To ensure integrity of randomization, clinical trial authorities should provide guidance encouraging the uniform use of central randomization.
Despite evidence that study personnel can and sometimes do tamper with envelopes, thus jeopardizing randomization, some clinical trials authorities, including the Cochrane Collaboration, maintain that envelopes adequately conceal allocation. Given the apparently conflicting evidence and recommendations, we explored the views of clinical trialists regarding the issue.
Objectives:
To evaluate clinical trialists’ views regarding the merits of using central randomization versus envelopes to conceal allocation in randomized controlled trials, and to test whether examples of apparent failure of envelopes could influence these views.
Methods:
A web-based survey administered to a random sample (n = 1926) of corresponding authors of randomized controlled trials published in one of 119 Core Clinical Journals between 1 January 2011 and 31 December 2012.
Results:
Four-hundred and ninety (490) participants completed the survey (25.4% response rate). Initially, 299 participants (61.0%) preferred using central randomization over envelopes to conceal allocation; nevertheless, 316 (64.5%) participants expressed views that envelopes are an adequate method to conceal allocation. After participants were shown examples that suggested envelopes’ vulnerability to manipulation, significantly more participants (69.0%) preferred central randomization (P value < 0.001), and significantly fewer participants (44.9%) expressed views that envelopes are an adequate method to conceal allocation (P value < 0.001).
Conclusions:
Although most trialists prefer central randomization to conceal allocation, most also considered envelopes an adequate concealment method, and a substantial minority continued in this view after viewing examples of the apparent vulnerability of envelopes to manipulation. Thus, the dangers of using envelopes and the desirability of consistent use of central randomization are underappreciated by clinical trialists, but empirical demonstration of envelopes' failure can influence trialists' views. To ensure integrity of randomization, clinical trial authorities should provide guidance encouraging the uniform use of central randomization.