Factors that influence the applicability of sham needle in acupuncture trials - Two randomized, single-blind, crossover trials with acupuncture-experienced subjects

Objectives: In recent years the retractable type of sham needle has been anticipated to be a possible solution for masking patients in acupuncture research. However, this needle has been intended mainly for acupuncture-naive subjects. The authors' goal in this study was to assess the validity of the retractable type of sham needle. Methods: The authors conducted two randomized, single-blind, crossover trials with acupuncture-experienced subjects. Different acupuncture points were used in each trial (a LI-4 trial and a BL-23 trial). The subjects received two sessions of different stimulations in each trial. A Park Sham Needle was used in one session, a genuine acupuncture needle in the other. Results: In the LI-4 trial, all of the 21 subjects (100%) felt penetration with the genuine needle, but only 7 of the 20 subjects (35%) felt a similar sensation with the sham needle (P=0.0002). Fifteen of the 21 subjects (71%) felt a dull sensation with the genuine needle, but only 4 of the 20 subjects (20%) felt a similar sensation with the sham needle (P=0.01). In the BL-23 trial, 14 of the 20 subjects (70%) felt penetration with the genuine needle and 10 of the 20 subjects (50%) felt "penetration" with the sham needle (P=0.39). Eight of the 20 subjects (40%) felt a dull sensation with the genuine needle and 2 of the 20 subjects (10%) did with the sham needle (P=0.109). Conclusions: Potential factors that influence the applicability of "placebo" needling include not only intertester variability but also the patient's knowledge and experience of acupuncture, acupuncture point selection, the visual impact of needling, and so on.