Papers

Informing participants of allocation to placebo at trial closure: postal survey

Zelda Di Blasi, PhD student, ^a Ted J Kaptchuk, assistant professor, ^b John Weinman, professor, ^c Jos Kleijnen, director. ^d

^a Department of Health Sciences, University of York, York YO10 5DD, ^b Osher Institute, Harvard Medical School, 401 Park Drive, Boston, MA 02215, USA, ^c Unit of Psychology, Guy's, King's, and St Thomas's School of Medicine, London SE1 9RT, ^d NHS Centre for Reviews and Dissemination, University of York, York YO10 5DD

Correspondence to: Z Di Blasi zdb1{at}york.ac.uk

Objectives: To assess whether and how investigators of placebo controlled randomised trials inform participants of their treatment allocation at trial closure and to assess barriers to feedback.
Design: Postal survey with a semistructured questionnaire.
Participants: All investigators who published a placebo controlled randomised trial in 2000 in five leading medical journals, and a random sample of 120 trials listed in the national research register database.
Main outcome measures: Number of investigators who informed participants of their treatment allocation at trial closure, methods for delivering the information, and barriers to unmasking treatment.
Results: 45% of investigators informed either all or most participants of their treatment allocation, and 55% did not inform any participant or only informed those who asked. The main reasons for not informing participants were that the investigators never considered this option (40%) or to avoid biasing results at study follow up (24%).
Conclusion: Further research is required to examine sensitive ways to communicate treatment information to trial participants.

What is already known on this topic Information is poor on the nature, extent, and effect of informing participants of placebo controlled randomised trials about their treatment allocation at trial closure Less than 50% of participants receiving placebo are informed about their treatment allocation What this study adds No standard procedure is available for informing patients of their treatment arm or of study results at the end of a trial Effective and sensitive ways of communicating treatment allocation to participants are required, as is information on the effects on placebo responders