A sensitivity analysis for subverting randomization in controlled trials

In some randomized controlled trials, subjects with a better prognosis may be diverted into the treatment group. This subverting of randomization resu lts in an unobserved non-compliance with the originally intended treatment assignment. Consequently, the estimate of treatment effect from these trial s may be biased. This paper clarifies the determinants of the magnitude of the bias and gives a sensitivity analysis that associates the amount that r andomization is subverted and the resulting bias in treatment effect estima tion. The methods are illustrated with a randomized controlled trial that e valuates the efficacy of a culturally sensitive AIDS education video. Copyr ight (C) 2001 John Wiley & Sons, Ltd.