Manual therapy remains a guideline-compliant, first-line therapeutic option for back pain. Yet, maintaining methodological quality in randomized controlled trials of manual therapy interventions poses challenges, particularly concerning: (a) The design of adequate 'sham' controls and (b) the blinding status of participants and outcome assessors. Optimal implementation of large-scale manual therapy trials requires testing the feasibility of control manual therapy interventions and effective blinding of participants and outcome assessors. Even when conducted in healthy populations and non-clinical settings, blinding feasibility trials remain an opportunity for methodological advancement in the field of manual medicine, and a research priority for unbiased treatment effect estimation in future trials.~The primary objective of this methodological trial was to quantitatively assess blinding feasibility among participants (graduate students enrolled in an epidemiology Ph.D. course) assigned to an active or control intervention immediately after a one-time intervention session. The secondary objective was to assess blinding feasibility among outcome assessors and explore factors influencing perceptions about intervention assignment among participants and outcome assessors. These two objectives contributed to obtaining valuable preliminary measures of blinding (blinding indices) for a future methodological blinding feasibility trial to be carried out in a real-world clinical setting.
There is marked uncertainty regarding the feasibility of achieving adequate blinding in randomized controlled trials of manual therapy. In other words, whether participants and outcome assessors can accurately perceive randomly assigned interventions is unclear. This feasibility trial was conducted as part of a doctoral epidemiology course at the University of Zurich, Switzerland. Within the practice-based context of the class and using a study population of healthy graduate students enrolled in the course, the investigators aimed to evaluate blinding of participants randomly assigned (similar to tossing a coin) to one of two manual therapy interventions (active versus control). The investigators also aimed to assess blinding among outcome assessors.