Double blinding with a new placebo needle: a further validation study.
BACKGROUND
The masking properties of a new, non-penetrating, double-blind placebo acupuncture needle were demonstrated. Practitioners correctly identified some of the needles; if they were confident in this opinion, they would be unblinded.


OBJECTIVE
To investigate the clues that led to correct identification, and the confidence in this decision.


METHODS
Ten acupuncture practitioners, blindly and randomly, applied 10 each of three types of needle to the shoulder: blunt, non-penetrating needles that pressed the skin ('skin-touch placebo needle'); new non-penetrating needles that penetrated soft material (stuffing) but did not reach the skin ('non-touch control needle'); matching penetrating needles. Afterwards, practitioners were asked to judge the type of needle, their confidence in their decision and what clues led them to their judgements.


RESULTS
Of the 30 judgements made by each practitioner, the mean number of correct, incorrect and unidentifiable answers were 10.4 (SD 3.7), 15.2 (SD 4.9) and 4.4 (SD 6.1), respectively. There was no significant difference in the confidence scores for 104 correct (mean, 54.0 (SD 20.2)%) and 152 incorrect (mean, 50.3 (SD 24.3)%) judgements. Twelve needles were identified with 100% confidence-three correct, and nine incorrect. For needles correctly identified, the proportions of non-touch (p = 0.14) and skin-touch (p = 0.17), needles were no greater than chance, but the proportion of penetrating needles correctly identified exceeded chance (p < 0.01). 53% of judgements were made from the "feeling of needle insertion", but 57% of these were wrong.


CONCLUSIONS
Practitioners had a slight tendency to guess the penetrating needles correctly, but were uncertain about most of their judgments, posing only a very small risk to double blinding.
Department of Acupuncture and Moxibustion, Faculty of Health Sciences, Tokyo Ariake University of Medical and Health Sciences, 2-9-1 Ariake, Koto-ku, Tokyo 135-0063, Japan. takakura@t-ariake.ac.jp
Nobuari
N
Takakura
Miho
M
Takayama
Akiko
A
Kawase
Ted J
TJ
Kaptchuk
Hiroyoshi
H
Yajima
D015670:Acupuncture Therapy / Q000295:instrumentation* / Q000379:methods*; D000328:Adult; D002983:Clinical Competence; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009339:Needles; D010919:Placebos; D012016:Reference Values; D015203:Reproducibility of Results; D012107:Research Design; D011795:Surveys and Questionnaires
D010919:Placebos