Systematic differences in care between groups caused by lack of blinding, not the treatment itself.
Performance bias occurs when participants or those delivering an intervention are aware of group allocation, leading to unintended differences in treatment, co-interventions, or effort between groups. This is a major concern in trials of exercise, manual therapy, or surgery, where blinding participants and therapists is often impossible or impractical. Risk-of-bias tools (e.g., Cochrane RoB 2) usually assess it via blinding of participants/personnel, but reviewers should judge severity in context rather than treating any unblinding as automatically fatal to a trial's validity.
This guide was auto-drafted and is pending editorial review.