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Double blinding with a new placebo needle: a validation study on participant blinding
  1. Nobuari Takakura1,2,3,4,
  2. Miho Takayama1,2,3,4,
  3. Akiko Kawase1,2,3,4,
  4. Hiroyoshi Yajima1,2,3,4
  1. 1Department of Acupuncture and Moxibustion, Faculty of Health Sciences, Tokyo Ariake University of Medical and Health Sciences, The Educational Foundation of Hanada Gakuen, Tokyo, Japan
  2. 2Second Department of Physiology, Showa University School of Medicine, Tokyo, Japan
  3. 3The Foundation for Oriental Medicine Research, Tokyo, Japan
  4. 4Japan School of Acupuncture, Moxibustion and Physiotherapy, The Educational Foundation of Hanada Gakuen, Tokyo, Japan
  1. Correspondence to Dr Nobuari Takakura, 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{at}tau.ac.jp

Abstract

Background A no-touch control needle in which the needle tip cannot reach the skin has been designed, and has been validated for practitioner blinding in a previous study but not for participant blinding.

Objective To test whether the no-touch control needle can effectively blind subjects.

Methods An acupuncturist applied, in turn, a no-touch control, skin-touch placebo and penetrating needle in one forearm of 80 healthy subjects. After removing each needle, the subjects were asked to judge the type of needle and rate the sensation of skin penetration/penetration-like or skin pressure/pressure-like pain on a 100 mm visual analogue scale.

Results The subjects correctly identified 67% of needles overall. 17 of the 80 no-touch control needles were judged as skin-touch, and one as penetrating. In addition, six skin-touch placebo needles, and no penetrating needles, were judged as no-touch. Half of the 80 skin-touch placebo needles and 65 of the 80 penetrating needles and two no-touch control needles elicited pain. Of 240 needles, the practitioner identified 120 correctly that did not fit the probability of 1/3 (χ2=30.00, p<0.01).

Conclusions The no-touch control needles may be used as a blind control for the acupuncture procedure, or to test the physiological effect of the skin-touch needles, but are not suitable for double-blind testing of the needle effect.

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Introduction

We devised a new no-touch control needle, in which the needle tip does not touch the skin, but have not yet validated it for patient blinding.1 Earlier, we designed and validated double-blind needles, consisting of a skin-touch placebo needle in which the tip presses against the skin and matching penetrating needle.2,,7 In our previous validation studies, experienced practitioners made statistically equal numbers of correct and incorrect judgements (or ‘guesses’) about the type of needle2 4; in another study, they made more incorrect judgements than correct ones.7 For ‘patient’ blinding, acupuncture-experienced volunteers made equal numbers of correct and incorrect judgements about the skin-touch placebo.4,,6 Furthermore, the subjects incorrectly identified approximately 32% of penetrating needles, which indicates that some penetrating needles were equally misjudged to be skin-touch placebo.4 7 Thus, we concluded that the skin-touch placebo needle was effective in patient and practitioner blinding; in combination with the penetrating needle, it has the potential for use in double-blind (patient and practitioner blinding) studies.1,,8

Although the blunt tip needles are ideal acupuncture placebos in some ways,9 researchers have questioned whether placebo needles that touch the skin might produce stimulation and, therefore, not be true placebos.9,,11 For this reason, we designed a new version of the placebo needle (ie, a no-touch control needle) in which the tip does not reach the skin, but which can still be matched to the validated double-blind skin-touch placebo and penetrating needles.1 The pedestal of the no-touch control needle touches the skin around the point, but we argue that it is physiologically inert as it does not stimulate the acupuncture point precisely, if this is regarded as a pin-point size. In our previous study practitioners incorrectly identified 66% of the no-touch control needles (including 17% unidentified),1 which indicates that the no-touch control needles are effective for practitioner blinding.

The aim of this study was to test whether the no-touch control needle was effective for blinding subjects. We tested the blinding effectiveness of no-touch control needles in acupuncture-experienced volunteers by employing no-touch control, skin-touch placebo and penetrating needles.

Methods

Participants

Eighty healthy volunteers (mean±SD age 27.1±6.9 years, 48 men, 32 women) who were familiar with receiving acupuncture from the acupuncture school (Japan School of Acupuncture, Moxibustion and Physiotherapy, Tokyo, Japan) participated in this study as experimental subjects. We recruited the acupuncturist from the teaching staff. Before the study, the purpose and format were explained to the subjects and the practitioner, who provided written consent. The study was approved by the ethics committee of the Showa University School of Medicine.

Design of double-blind needles

We used three types of needles in this study: (a) the ‘no-touch control needle’, the tip of which cannot reach the skin1; (b) the ‘skin-touch placebo needle’, the tip of which presses against the skin but cannot penetrate it; (c) the ‘penetrating needle’, with 5 mm insertion depth (figure 1).1,,8 These needles have been described in detail elsewhere.1 2 Briefly, the no-touch control and the skin-touch placebo needle are identical to the penetrating needle except that the needle is shorter and has a blunt tip: the no-touch control needle is shorter than the skin-touch placebo needle. The guide is opaque, and has an adherent pedestal which attaches to the skin. The upper part of the guide tubes of the three kinds of needles is stuffed to disguise the feel of the needle insertion. The lower part of the guide tube of the no-touch control and the skin-touch placebo needle is also stuffed and gives the practitioner the impression that the needle is penetrating the body. Every needle has a stopper that prevents the needle handle from advancing further than the specified position. Before use the needle tips were set at just above the skin surface in the penetrating needle, and just above the upper surface of the lower stuffing in the skin-touch placebo and the no-touch control needle. In this way, the no-touch control and skin-touch placebo needle are indistinguishable from the penetrating needle in both appearance and feel. The diameter of the needles was 0.16 mm.1,,8

Figure 1

Double-blind needles. The no-touch control (left), skin-touch placebo (middle) and penetrating needles (right) comprise an opaque guide tube and upper stuffing to give resistance to the needle body during its passage through the guide tube. Each needle has a stopper, which prevents the needle handle from advancing further when the tip of the needle reaches the specified position. The pedestal on each needle is adhesive, allowing it to stick firmly to the skin surface. The left and right needles shown for each type of needle are before and after needle insertion, respectively. The needle body of the no-touch control needle (left cross section) is shorter than the guide tube, and the needle body of the skin-touch placebo needle (middle cross section) is just long enough to allow its blunt tip to press against the skin, but the needle body of the penetrating needle (right cross section) is longer than the guide tube by an amount equal to the insertion depth when the needle body is advanced as far as possible. The no-touch control and skin-touch placebo needles contain lower stuffing to give a similar sensation to that of skin puncture and tissue penetration.

Protocol

For each subject, we prepared a set of three sterilised needles consisting of a penetrating, a skin-touch placebo and a no-touch control needle sealed in a small opaque container. Before the trial, each subject and the practitioner were informed that three needles would be applied in each forearm and that either no-touch control, skin-touch placebo or penetrating needle would be used for each needle application.

Three points on the triple energiser meridian on the posterior forearm were used to apply the needles at one fourth (distal point), two fourths (middle point) and three fourths (proximal point) of the length of the meridian from the dorsal wrist crease to the prominence of the elbow (the olecranon).12 The practitioner took a needle randomly from a set of the three types of needles in the container and applied the first needle at the proximal point in each subject. Then, one of the remaining needles was applied at the middle point, and the last one was applied at the distal point. Each needle was applied until the stopper made contact with the top of the guide tube. Immediately after, the practitioner pulled the needle out to the initial position.1,,7 The practitioner applied three types of needles using the ‘alternate twirling’ (rotating the needle clockwise and counterclockwise alternately) technique. She used the right forearm in the first and fourth subject, the left forearm in the second and third subject, repeating this pattern for the remaining subjects. The subjects were not blindfolded and thus they could see the needling site.

After each needle removal, an assistant who was blinded to true nature of needles handed the subject the questionnaires. We asked the subjects to rate the sensation of skin penetration/skin penetration-like or skin pressure/pressure-like pain (SPP) on a visual analogue scale (VAS), ranging from 0 (no pain) to 100 (the most intense SPP imaginable).4 7 8 They also reported whether they felt de qi.4 7 8 The subjects were asked to record whether they thought the needle was ‘penetrating’, ‘skin-touch’, ‘no-touch’ or ‘unidentifiable’.1,,8 We did not tell the subjects that they would receive all three types of needle, but of the 80 subjects, 29 chose three types of needles which did not fit the expected value (6/27) (χ2=5.199, p=0.02). The subjects then rated their confidence in their guess of the type of needle (ie, the degree of certainty that their decision was correct) on a VAS, the end points of which were 0 for no confidence and 100 for complete confidence.1 7 To confirm achievement of practitioner blinding and reduce the chance of influence, we also asked the practitioner to record her judgements on the nature of needles and her confidence in those judgements.1,,8

We employed the assistant to take all possible precautions to ensure that the identity of the needle was not revealed to the subjects or the practitioner, and that their guesses could not be influenced by each other. The subject and practitioner filled in a questionnaire in silence and were unaware of each other's answers. The assistant collected the completed questionnaires face down. Thus there was no possibility that the subject and practitioner would be influenced by each other by hearing or looking at each other's reports.

Statistical analysis

We used the Kruskal–Wallis test to detect statistical differences between the three interventions and the Mann–Whitney U test to identify pairwise group differences in the confidence of the subjects' and practitioner's identifications and intensity of SPP. The χ2 test was used to determine whether the numbers of needles fitted an expected probability. All statistical analyses were performed using IBM SPSS Statistics 18 (IBM Japan, Tokyo). The true identity of the needle was not revealed until after the results had been tabulated.

Results

Effectiveness of subject blinding

As table 1 shows, 23 (29%) of the 80 no-touch control needles were misidentified, including those that could not be identified. The subjects misidentified 53% of the 80 skin-touch placebo needles, of which 14% were judged to be no-touch. For the penetrating needles, 19% were misidentified, including those that could not be identified. No penetrating needle was guessed to be a no-touch needle.

Table 1

Number of needles (confidence score in subjects' judgements, mean±SD) associated with subjects' judgements

Of the 240 needles applied, overall the subjects identified 160 (67%) correctly with mean±SD confidence of 80.2±21.4 on the 100 mm VAS, 68 (28%) incorrectly with confidence of 78.7±19.2 and 12 (5%) needles were reported as unidentifiable. There was no significant difference in the subjects' confidence between 31 skin-touch placebo and 65 penetrating needles judged as penetrating (p=0.26).

Pain on needle application

Of the 80 no-touch control needles, 3% elicited SPP, and no needles judged as no-touch elicited SPP (table 2). Of the 80 skin-touch placebo and penetrating needles, 50% and 81% elicited SPP, respectively. There was no significant difference between SPP elicited by the penetrating and skin-touch placebo needles (p=0.09). Thirty-three (41%) penetrating, 13 (16%) skin-touch and 2 (3%) no-touch control needles elicited de qi.

Table 2

Number of needles elicited skin penetration/skin penetration-like or skin pressure/pressure-like pain (intensity, mean±SD) associated with subjects' judgements

Practitioner blinding

As table 3 shows, the respective numbers of correct/incorrect (including unidentified needles) answers of the acupuncturist were 120/120 which did not fit an expected 1:2 ratio (χ2=30.00, p<0.01). However, there was no significant difference in the practitioner's confidence score of her judgements between the no-touch control, skin-touch placebo and penetrating needles judged as no-touch (p=0.54), skin-touch (p=0.09) and penetrating (p=0.17), respectively.

Table 3

Number of needles (confidence score in practitioner's judgements, mean±SD) associated with practitioner's judgements

Discussion

In this study, the subjects rarely misidentified no-touch control needles as penetrating, or skin-touch placebo needles and penetrating needles as no-touch. Therefore, in future clinical trials no-touch control needles may be used as a suitable control for the ritual aspects of acupuncture treatment, but not to eliminate any patient-oriented biases from expecting to receive treatment with penetrating needles.

For subjects, SPP was an important clue in identifying the true nature of the penetrating needle.4 7 The skin-touch placebo needles were well blinded to the subjects because of the similarity of SPP elicited with the penetrating needles. Because of the very nature of the no-touch control needles, it might be inherently difficult to make subjects think that they are skin-touch or penetrating; and it seems almost impossible to identify the penetrating and skin-touch placebo needles as no-touch. Unexpectedly, however, approximately 20% of the no-touch control needles were misidentified as skin-touch. This result shows that the no-touch control needle might be a potential tool for investigating whether skin pressure with a blunt tip needle to an acupoint is a ‘clinically’ inert placebo.

For the penetrating and skin-touch placebo needles, although the subjects were uncertain about their judgements, their confidence scores were relatively high for both the correctly and incorrectly identified needles. These high confidence scores could be because subjects had sensations elicited with penetrating or placebo acupuncture which gave an important clue in guessing the nature of the needle.4 7 In contrast to real and placebo pills which do not have such sensations, it is possible that patients' beliefs have a significant impact on the efficacy of acupuncture treatment. In the case of sham/placebo needles in acupuncture trials, therefore, analysis taking account of patients' judgements of the potential benefit from needle penetration, expectation or both, should be undertaken, in addition to an intention-to-treat analysis.

For practitioner blinding, the true nature of the skin-touch placebo needles was well blinded; but for the no-touch control and penetrating needles the practitioner blinding still resulted in a high number of correctly identified needles. The disparity in practitioner's guesses suggests that the potential for achieving complete practitioner blinding is limited. It is noteworthy, however, that practitioners were uncertain about most of their correct judgements, as in the previous study,1 and we think that the double-blind needles are a possible device for blinding practitioners.1,,8 The practitioner's guesses with confidence should be recorded to see whether the true identity of the needle is revealed in future clinical study. In the studies using the no-touch control, skin-touch placebo and penetrating needles, no-touch control needles could be used as control to eliminate practitioner-oriented biases, which would give us important information that could not be obtained by waiting list or other controls.1

The basic limitations of the double-blind needles have been described elsewhere.1 2 4 7 In addition, this study had the following limitations: we used only one practitioner, so intertester reliability was not tested; the subjects were healthy students in an acupuncture school; this study was not carried out in a clinical setting; the insertion depth was restricted to 5 mm; it cannot be denied that the second and third judgements of the participants were influenced by their previous judgements. Changes in practitioner, the subjects who receive needles or the insertion depth might produce different results of ‘patient’ blinding. Therefore, further validation is necessary, especially for the no-touch control needles.

Conclusion

The no-touch control needles may be used as a blind control for the acupuncture procedure, or to test the physiological effect of the skin-touch needles, but are not suitable for double-blind testing of the needle effect.

Acknowledgments

The authors thank Ikuo Homma (Second Department of Physiology, Showa University School of Medicine, Tokyo) for his support. The authors also express their appreciation to all the participants of this study.

References

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Footnotes

  • Funding The Educational Foundation of Hanada Gakuen, 20-1 Sakuragaoka-machi, Shibuya-ku, Tokyo 150-0031, Japan.

  • Competing interests NT and the Educational Foundation of Hanada Gakuen possess a US patent 6575992B1, a Canadian patent CA 2339223, a Korean patent 0478177, a Taiwanese patent 150135, a Chinese patent ZL00800894.9 (Title: Safe needle, placebo needle and needle set for double blind) and a Japanese patent 4061397 (Title: Placebo needle, and needle set for double-blinding) on the needles described in this manuscript. NT is a salaried employee of the Educational Foundation of Hanada Gakuen and has received research funding from the Educational Foundation of Hanada Gakuen.

  • Patient consent Obtained.

  • Ethics approval This study was conducted with the approval of the ethics committee of the Showa University School of Medicine.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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