Placebo effects in trials evaluating 12 selected minimally invasive interventions: a systematic review and meta-analysis

Objectives: To analyse the impact of placebo effects on outcome in trials of selected minimally invasive procedures and to assess reported adverse events in both trial arms. Design: A systematic review and meta-analysis. Data sources and study selection: We searched MEDLINE and Cochrane library to identify systematic reviews of musculoskeletal, neurological and cardiac conditions published between January 2009 and January 2014 comparing selected minimally invasive with placebo (sham) procedures. We searched MEDLINE for additional randomised controlled trials published between January 2000 and January 2014. Data synthesis: Effect sizes (ES) in the active and placebo arms in the trials’ primary and pooled secondary end points were calculated. Linear regression was used to analyse the association between end points in the active and sham groups. Reported adverse events in both trial arms were registered. Results: We included 21 trials involving 2519 adult participants. For primary end poin...