Towards more credible shams for physical interventions: A Delphi survey

Area of Science:

• Clinical Trials
• Research Methodology
• Physical Interventions

Background:

• Participant blinding is often inadequate in physical intervention trials.
• Therapist blinding is routinely omitted, hindering progress in determining intervention mechanisms.
• Effective blinding is vital for advancing the understanding of physical interventions.

Purpose of the Study:

• To identify key elements for designing credible sham interventions in physical trials.
• To enhance participant and therapist blinding through expert consensus.
• To improve the rigor of sham-controlled clinical trials.

Main Methods:

• A Delphi approach involving two expert groups: research methodology and deceptive/hypnotic techniques (including magicians).
• Three survey rounds, with items rated on a 9-point Likert scale.
• Consensus defined as ≥80% agreement within a 3-point category.

Main Results:

• Thirty-eight experts participated; 30 responded to at least one round.
• Five essential items reached consensus across both groups, focusing on participant beliefs, researcher interaction, and assessment standardization.
• Additional items reached consensus within individual groups, highlighting authentic information delivery and therapist behavior.

Conclusions:

• Cognitive influences are essential for believable sham interventions.
• Replicating tactile sensations is less critical than cognitive credibility of the overall intervention experience.
• Guidance is provided for designing more effective sham-controlled trials by focusing on cognitive factors and the entire intervention context.