Effects of previous experience with dry needling therapy on blinding effectiveness and pain outcomes in people with neck pain: A preliminary sham-controlled study

Background: Participants' previous experience with an intervention may be an important variable when conducting sham-controlled trials.Objective: This study explored if previous experience with dry needling (DN) influenced blinding effectiveness and pain outcomes, after the application of DN in patients with neck pain.Design: A preliminary randomized, sham-controlled study.Methods: Participants were randomized to receive a single session of real or sham DN. Previous experience with DN (yes/no) was recorded. Blinding effectiveness was assessed by asking participants to guess their group allocation (real/sham/not sure) 5 min post-intervention. Outcomes including pain intensity, pressure pain thresholds, and self-perceived improvement, were assessed by a blinded assessor at baseline, one- and seven-days post-intervention.Results: Of 50 patients recruited, 30 had previous experience and 20 did not. Fifty-seven percent (n =17/30) with previous experience and 35% (n = 7/20) without experience correctly identified their group allocation, but this difference was not significant (chi 2 = 2.333; P = 0.127). No interaction between previous experience and clinical outcomes were found, except that participants with previous experience receiving real DN showed greater improvements in pain during cervical rotation than those without previous experience at one (Delta -11.5 mm 95%CI -22.0 to -1.0 mm) and seven days (Delta -8.5 mm, -16.00 to -1.0 mm) post-intervention.Conclusions: Participants with previous experience were 22% more accurate at identifying their group allocation than those without experience, but the difference was not significant. Previous experience did not influence most clinical outcomes, except for pain intensity after real DN. Future studies evaluating effects of previous experience of DN should include more detailed information of previous experience.