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Randomized Controlled Trial
. 2008 Mar;34(2):234-41.
doi: 10.1016/j.jsat.2007.04.004. Epub 2007 Jun 27.

Can the blind see? Participant guess about treatment arm assignment may influence outcome in a clinical trial of bupropion for smoking cessation

Robert A Schnoll  1 , Leonard Epstein, Janet Audrain, Raymond Niaura, Larry Hawk, Peter G Shields, Caryn Lerman, E Paul Wileyto
Affiliations
Randomized Controlled Trial

Can the blind see? Participant guess about treatment arm assignment may influence outcome in a clinical trial of bupropion for smoking cessation

Robert A Schnoll et al. J Subst Abuse Treat. 2008 Mar.

Abstract

In a placebo-controlled bupropion smoking cessation trial, we examined blind integrity, the link between blind integrity and quit rates, and whether side effects and changes in nicotine withdrawal symptoms or mood were mechanisms through which blind integrity is threatened. At a 12-month follow-up, 498 participants indicated whether they thought they received bupropion, placebo, or were not sure. Potential mediators of treatment effects on treatment arm guess (i.e., side effects, withdrawal, and mood) were measured during treatment, and 7-day point prevalence cessation was assessed at the end of treatment (EOT) and at 6 and 12 months after quit date. Overall, 55% of participants guessed their randomization correctly. Compared to guessing not sure, participants who guessed they were taking bupropion were more than twice as likely to have been randomized to bupropion. Similarly, participants who guessed placebo were twice as likely to have been randomized to placebo. Treatment arm guess was associated with quit rates. Including treatment arm guess with actual treatment arm in models of quit rates significantly reduced the odds ratio for bupropion efficacy at the EOT and at 6 and 12 months after quit date. There was no evidence for mediation. In bupropion smoking cessation trials, blind failure may occur and participant guess about treatment arm assignment is associated with quit rates.

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Figures

Figure 1
Figure 1. Percent Randomized to Actual Treatment Arm by Treatment Arm Guess Category (N = 498)
Note: * Odds ratios reflect odds of actual assignment to bupropion versus placebo based on participant judgment, using “not sure” as the reference group. Those judging that they received placebo were less likely to be in the bupropion group than those not sure (OR = 0.55, p = 0.02), and those judging that they received bupropion were more likely to be in the bupropion group than those not sure (OR = 2.09, p = 0.005).
Figure 2
Figure 2. Longitudinal View of Abstinence Rates by Actual Treatment Arm and Treatment Arm Guess Across Time (N = 498)
Note. While overall abstinence declined over time, both actual assignment to treatment arm and judgment about treatment arm assignment improve abstinence at all timepoints (see Table 3). Effects of judgment about treatment arm did not differ across timepoints.
Figure 3
Figure 3. Path Diagram of Suspected Mediators of Blind Failure (N = 381)
Note. Total effect of actual treatment arm on treatment arm guess is 0.308. Total direct effect of actual treatment arm is 0.260, while total indirect effect is 0.048. Dotted lines represent non-significant beta values.
See this image and copyright information in PMC

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