Double‐blind and single‐blind retractable placebo needles

Choi and Lam discuss placebo acupuncture needles and recommended the most appropriate method to blind patients in acupuncture studies 1. However, the reported information concerning the placebo acupuncture needles and their effect on blinding were not accurate, which can mislead readers. In fact, there are single-blind and double-blind placebo/sham needles, which differ in their structure. The Takakura double-blind placebo needle described by Choi and Lam 1 is designed to blind both the patient and practitioner, and it is not retractable but has a stopper to prevent the blunt tip of the needle from further advance when the blunt tip reaches the skin. To blind practitioners, the guide tube of a double-blind needle is stuffed to make the resistance felt by the practitioner upon needle insertion indistinguishable between penetrating and placebo needles 2. In contrast, single-blind placebo/sham needles, such as the Streitberger and Park needles, are designed to blind only patients, and they are retractable but not equipped with a stopper. When the blunt tip of the needle reaches the skin, the needle body is pushed into a hollow needle handle, hence blinding the patient but not the practitioner 2. Furthermore, the structure of single-blind sham needle used in Juel's study 3, which has been cited by Choi and Lam 1, is different from the Streitberger and Park needles, and thus the sharp tip of a hollow inner tube provides patients with a pricking sensation 3. Choi and Lam describe that placebo needles to blind practitioners are retractable and have a stopper 1. This inaccurate description leads the reader to confuse single-blind needles with double-blind needles. When blinding patients with retractable single-blind placebo/sham needles, most instances of both penetrating and placebo needles were guessed as ‘penetrating the skin’ 4. This indicates that successful patient blinding scenario of ‘unblinded’ in real arm/'opposite guess' in placebo arm 5 is feasible. Choi and Lam should ensure that their reported rates of correct treatment identification by patients (68%) and practitioners (83%) 1 correspond to the results obtained with non-retractable double-blind needles. Although, in cases where blinding the practitioner is difficult, limiting the interaction/communication between the patient and the practitioner may seem the best approach 1, vital non-verbal interaction/communication can occur between them, either consciously or unconsciously 6. In trials where double-blind needles were used, most patients and practitioners were unsure of their guesses at whether the needles were penetrating or placebo 2. Furthermore, an inert placebo condition, which does not stimulate the acupoint with the needle tip, is possible when a no-touch double-blind needle is used as control for both skin-touch placebo needles and penetrating needles. Imperfect or partial blinding is better than no blinding 5. Placebo/sham acupuncture needles should be used in clinical trials to exclude bias as much as possible, and the success of blinding should be evaluated towards a better interpretation of the reliability of results to supplement imperfect blinding 4.