"I assumed that one was a placebo": exploring the consent process in a sham controlled acupressure trial

In clinical trials where participants are likely to be able to distinguish between true and sham interventions, informing participants that they may receive a sham intervention increases the likelihood of participants 'breaking the blind' and invalidating trial findings. The present study explored participants' perceptions of the consent process in a sham controlled acupressure trial which did not explicitly indicate participants may receive a sham intervention.

Nested qualitative study within a randomised sham controlled trial of acupressure wristbands for chemotherapy-related nausea. Convenience sample of 26 patients participated in semi-structured interviews. Interviews were audio-recorded and transcribed verbatim. Transcripts analysed thematically using framework analysis.

Study conducted within three geographical sites in the UK: Manchester, Liverpool, and Plymouth.

All participants indicated that they believed they were fully informed when providing written consent to participate in the trial. Participants' perceived it was acceptable to employ a sham intervention within the trial of acupressure wristbands without informing potential participants that they may receive a sham treatment. Despite the fact that participants were not informed that one of the treatment arms was a sham intervention the majority indicated they assumed one of the treatment arms would be placebo.

Many trials of acupuncture and acupressure do not inform participants they may receive a sham intervention. The current study indicates patients' perceive this approach to the consent process as acceptable. However, the fact participants assume one treatment may be placebo threatens the methodological basis for utilising this approach to the consent process.