Information about patients' preference must be obtained first

EDITOR—Torgerson and Sibbald discuss the difficulties of assessing the relative merits of treatments when patients have strong preferences for one of the alternatives.1 In these circumstances, however, patients should not be expected to participate in randomised comparisons, and neither should the professionals caring for them.

It is important to consider the bases of these preferences, particularly as there is a widespread and unsupported belief that new treatments are likely to be superior to existing alternatives.2 For example, it seems that people with diabetes who were being recruited to a randomised comparison of insulin pumps with conventional management were left with the impression that pumps represented an important advance (C Bradley, personal communication). Not surprisingly, therefore, those allocated to pumps were pleased, while those allocated to conventional management were disappointed. Randomisation thus created comparison groups that were incomparable in these psychological characteristics, and this may have had implications for compliance and evaluation of treatment outcome.3

Bradley's response3 was to propose the partially randomised patient preference design to which Torgerson and Sibbald refer. Unfortunately, this does not help because it cannot distinguish between an effect of preferences and an effect of confounding of preferences with prognosis. Since it is impossible to randomise between sincerely held preferences, measuring their effects reliably requires a more complicated design, which was suggested originally by Rucker4 and recently discussed by McPherson et al.5 In this design, people are randomised between either a randomised comparison or …