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. 2002 Dec 7;325(7376):1329.
doi: 10.1136/bmj.325.7376.1329.

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

Zelda Di Blasi  1 , Ted J Kaptchuk, John Weinman, Jos Kleijnen
Affiliations

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

Zelda Di Blasi et al. BMJ. .

Abstract

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.

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