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

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.