Blinding strategies in dry needling trials: Systematic review and meta-analysis

Blinding of participants and therapists in trials of physical interventions is a significant and ongoing challenge. There is no widely accepted sham protocol for dry needling. Purpose: The purpose of this review was to summarize the effectiveness and limitations of blinding strategies and types of shams that have been used in dry needling trials. Data Sources: Twelve databases were searched from inception to February 2016. Study Selection: Trials that compared active dry needling with a sham that simulated dry needling were included. Data Extraction: The main domains of data extraction were participant/therapist details, intervention details, blinding strategies, blinding assessment outcomes, and key conclusions of authors. Reported blinding strategies and sham types were synthesized descriptively, with available blinding effectiveness data synthesized using a chance-corrected measurement of blinding (blinding index). Data Synthesis: The search identified 4894 individual publications with 27 trials eligible for inclusion. In 22 trials, risk of methodological bias was high or unclear. Across trials, blinding strategies and sham types were heterogeneous. Notably, no trials attempted therapist blinding. Sham protocols have focused on participant blinding using strategies related to group standardization and simulation of tactile sensations. There has been little attention given to the other senses or cognitive strategies to enhance intervention credibility. Nonpenetrating sham types may provide effective participant blinding. Limitations: Trials were clinically and methodologically diverse, which limited the comparability of blinding effectiveness across trials. Reported blinding evaluations had a high risk of chance findings with power clearly achieved in only 1 trial. Conclusions: Evidence-based consensus on a sham protocol for dry needling is required. Recommendations provided in this review may be used to develop sham protocols so that future protocols are more consistent and potentially more effective.