Abstract
Context:
It’s difficult to conduct experiments using a double-blind design in controlled clinical trials of acupuncture. To resolve this problem with blinding, we designed double-blind needles (DBNs) with stuffing to mimic the resistance felt during insertion of a regular acupuncture needle. Results of the past studies using 0.16-mm-diameter DBNs found that the resistance felt by the acupuncturists during insertion successfully blinded them.
Objective:
The study intended to compare the effects on an acupuncturist’s blinding when the practitioner used penetrating DBNs with 0.14, 0.16, 0.18, and 0.20 mm diameters.
Design:
We conducted a double-blind randomized trial.
Setting:
The study took place at the Japan School of Acupuncture, Moxibustion. and Physiotherapy in Tokyo, Japan.
Participants:
The participant was one licensed acupuncturist who performed 320 needle insertions during acupuncture for 20 healthy students, who were familiar with acupuncture and who attended the Japan School of Acupuncture, Moxibustion, and Physiotherapy.
Methods:
The acupuncturist was informed she would administer a penetrating or non-penetrating needle; however, only penetrating needles were used. She inserted the four sizes of needles in both of each student’s dorsal forearms using an alternating twirling technique. This procedure was repeated once more on another day, with at least one day between sessions.
Primary Outcome Measures:
After the acupuncturist removed each needle, we asked her to guess: (1) the type of needle inserted, (2) her level of confidence in the guess, and (3) the clues that contributed to her guess. A chi-squared test was used to determine whether the ratio of correctly or incorrectly identified needles met an expected probability of 0.5 for each needle diameter.
Results:
Of the 320 needle insertions, the acupuncturist correctly identified 54% of 0.14 mm, 45% of 0.16 mm, 46% of 0.18 mm, and 50% of 0.20 mm needle insertions. The correct and incorrect ratios of identified needles were fitted with a probability of 0.5, with no significant differences in the acupuncturist’s confidence (p=0.16). In 99% of the tests, the cue that contributed to the acupuncturist’s guess was the feeling of the needle insertion.
Conclusion:
These findings indicate that the differences in the diameters of DBNs from 0.14 to 0.20 mm didn’t significantly affect the acupuncturist’s blinding.
INTRODUCTION
The double-blind, randomized controlled trial is the most rigorous scientific method used to test medical hypotheses,1 but it’s difficult to conduct experiments using a double-blind design in controlled clinical trials of acupuncture.2 This is because in acupuncture the needle insertional force transmits a sense of resistance to the acupuncturists’ fingers when an acupuncture needle is inserted into an patient’s body.
To resolve this problem with blinding, we designed double-blind needles (DBNs). Each set consists of a penetrating needle and a matched non-penetrating needle (Figure 1). DBNs contain stuffing that mimics the resistance felt by the acupuncturist’s fingers during insertion of a regular acupuncture needle.3–8 Results of our past studies using 0.16-mm-diameter DBNs4,5 have indicated that the resistance between the needle and the tissue felt by the acupuncturists during insertion successfully blinded them.
Figure 1.
A set of double-blind acupuncture needles (DBNs)
When acupuncturists, however, use diameters of DBNs other than 0.16 mm, the ability to blind them to the needle’s size is unknown. In basic science studies and clinical trials, 0.14, 0.16, 0.18, and 0.20 mm diameters of acupuncture needles used.9–14 Okamura et al have demonstrated that an increase in needle diameter causes an increase in the needle’s insertional force,15 which indicated that acupuncturist’s blinding with 0.14, 0.18, and 0.20 mm diameter DBNs could be affected or broken.
Therefore, it’s necessary to validate the ability to blind acupuncturists with DBNs using the 3 additional common diameters of needles—0.14, 0.18, and 0.20 mm—because the perceived needle insertion force may change with the insertion of each different diameter.16
No studies comparing the effects of acupuncturist blinding with needles of these diameters have been performed at the current time.
The aim of the current study was to compare the effects on an acupuncturist’s blinding when the practitioner uses penetrating needles with 0.14, 0.16, 0.18, and 0.20 mm diameters.
METHODS
We conducted a double-blind randomized trial.
Participants
The study took place at the Japan School of Acupuncture, Moxibustion, and Physiotherapy in Tokyo, Japan. The participant was one licensed acupuncturist who performed 320 needle insertions during acupuncture for 20 healthy students who were familiar with acupuncture and who attended the Japan School of Acupuncture, Moxibustion, and Physiotherapy.
The acupuncturist was 45 years old, with 7 years of experience, and usually used needles with 0.16 or 0.18 mm diameters in her daily acupuncture practice.
The study’s purpose and protocol were explained to the students and written consent was obtained. This study was approved by the Ethics Committee of the Tokyo Ariake University of Medical and Health Sciences (approval number 30).
Procedures
The DBNs are unidentifiable from their appearance as to whether they are penetrating or non-penetrating needles.
The diameters of the penetrating needles used in the DBN device in the current study were 0.14, 0.16, 0.18, and 0.20 mm. All needles were stainless steel, and the insertion depth of each needle was 5 mm.4,5 The structure of the DBN device has been described in detail elsewhere.3
In the current study, the acupuncturist and the 20 participants were informed they would use or receive, respectively, either penetrating or non-penetrating needles; however, only penetrating needles were used.4
The acupuncturist inserted the first needle in the left dorsal forearm at a location 10 mm proximal from one-sixth the distance from the dorsal-wrist crease to the olecranon using the tapping-in method for skin penetration.7 The acupuncturist inserted the needle using an alternating twirling technique until the stopper made contact with the top of the inner guide tube.7 Then the needle was removed.
This procedure was repeated 3 more times on the same dorsal forearm using the needles with the 3 other diameters; they were inserted at 10-mm intervals from the first insertion. Then the 4 sizes of needles were inserted into the right dorsal forearm using the same procedure. This procedure was repeated once more on another day, with at least one day between sessions.
Outcome Measures
Immediately after each needle was removed, the acupuncturist was asked to guess: (1) the type of needle inserted—penetrating, non-penetrating, or unidentifiable, (2) her level of confidence in the guess, and (3) the clues that contributed to her guess. The acupuncturist then rated her confidence in the guess on a visual analog scale (VAS), with zero at one end indicating no confidence and 100 at the other end indicating complete confidence. The acupuncturist also estimated the diameter of each needle.
The acupuncturist selected the clues she used to guess the identity of the needle from the following (1) to (10) options which were revealed in the previous study4: (1) the participant’s facial expression; (2) body movement of the participant; (3) the feeling of the needle insertion in the insertion hand; (4) the feeling of the needle removal in the insertion hand; (5) the feeling of the needle in the supporting hand, which held the guide tube and DBN device in place; (6) bleeding; (7) subcutaneous bleeding; (8) lack of bleeding; (9) a red flare at the needle insertion site; and (10) “Is there any clues except for (1) to (9) option, if so, please you write it down here”.
Statistical Analysis
A chi-squared test—a test of equality—was used to determine whether the ratio of correctly or incorrectly identified needles met an expected probability of 0.5 for each needle diameter and to determine whether the acupuncturist’s identified clues were related to the acupuncturist’s guesses or estimates—a test for independence.
For the effectiveness of blinding, Bang’s blinding index (BI) for each of the 4 diameters was calculated by the numbers of correct, incorrect, and unidentified guesses.17,18 A BI from −0.2 to 0.2 indicated random guesses, based on the proposed criteria for the BI.17
The acupuncturist’s confidence score of correct/incorrect identifications with one and two clues from (1) to (10) option were compared using the Mann-Whitney U test. Comparisons among the 4 different needle size groups were made using the Kruskal-Wallis test.
With the exception of the BI, statistical analyses were performed with SPSS version 18.0 (SPSS, Tokyo, Japan). The calculation procedures used for the BI were based on the previous study.17,18
RESULTS
Table 1 shows the number of the acupuncturist’s guesses for each needle diameter and her confidence score for those needle guesses. Correct guesses indicate she guessed the needles to be penetrating, and incorrect guesses indicate she guessed the needles to be non-penetrating or unidentifiable.
Table 1.
Number of needles guessed correctly or incorrectly by the acupuncturist and confidence scores of her guesses
| Needle diameter | Acupuncturist’s guesses | Number (mean/median confidence score) of needles guessed as | Total | |||
|---|---|---|---|---|---|---|
| 0.14 mm | 0.16 mm | 0.18 mm | 0.20 mm | |||
| 0.14 mm | Correct | 7 (73.1/79.3) | 26 (61.0/76.4) | 10 (55.0/60.3) | 0 (−/−) | 43 (61.5/74.3) |
| Incorrect | 7 (58.0/68.8) | 22 (47.5/52.4) | 8 (49.5/56.9) | 0 (−/−) | 37 (49.9/64.7) | |
| 0.16 mm | Correct | 4 (86.7/84.0) | 16 (60.5/74.3) | 15 (54.3/50.0) | 1 (83.7/83.7) | 36 (61.5/76.4) |
| Incorrect | 1 (75.2/75.2) | 17 (41.9/36.1) | 21 (57.0/70.3) | 5 (42.9/17.5) | 44 (50.0/60.6) | |
| 0.18 mm | Correct | 0 (−/−) | 8 (34.4/21.7) | 12 (67.7/78.2) | 17 (72.6/80.8) | 37 (62.7/78.6) |
| Incorrect | 0 (−/−) | 12 (57.9/78.3) | 20 (51.8/59.6) | 11 (63.6/75.7) | 43 (56.5/75.7) | |
| 0.20 mm | Correct | 0 (−/−) | 2 (55.1/55.1) | 16 (57.6/61.0) | 22 (65.4/72.6) | 40 (61.8/71.7) |
| Incorrect | 1 (0.0/0.0) | 4 (58.9/74.7) | 19 (47.6/51.3) | 16 (47.6/45.0) | 40 (47.5/51.3) | |
| Total | Correct | 11 (78.1/80.7) | 52 (56.5/72.1) | 53 (58.5/68.4) | 40 (68.9/80.1) | 156 (61.9/74.5) |
| Incorrect | 9 (53.5/68.8) | 55 (48.9/56.9) | 68 (51.9/63.4) | 32 (52.4/70.6) | 164 (51.1/64.5) | |
For “Acupuncturist’s guesses”, “Correct” indicates needles correctly guessed as “penetrated the skin”; “Incorrect” indicates needles incorrectly guessed as “not penetrated the skin” or “unidentifiable”.
Bold letters indicate needles correctly guessed as “penetrated the skin” with correct guesses of needle diameters by the acupuncturist.
The acupuncturist indicated she couldn’t guess for 4 insertions whether the needle was penetrating or non-penetrating; one used a 0.14-mm needle, one used a 0.16-mm needle, and 2 used a 0.20-mm needle.
The guesses for needles of the same diameter were fitted with a probability of 0.5: (1) 0.14 mm: X2=0.45, p=0.50; (2) 0.16 mm: X2=0.80, p=0.37; (3) 0.18 mm X2=0.45, p=0.50; and (4) 0.20 mm: X2<0.001, p=1.00. No significant differences were observed in the ratios of correctly and incorrectly identified needles among the 4 diameters (X2=1.39, p=0.71).
The BIs were 0.09, −0.09, −0.08, and 0.03 for the 0.14-, 0.16-, 0.18-, and 0.20-mm-diameter needles, respectively, which indicates random guesses for needles of every diameter.7
Concerning identification of correct needle diameters, the acupuncturist correctly identified 2.2%, 5.0%, 3.8%, and 6.9% of the needles for the 0.14, 0.16, 0.18, and 0.20 mm diameter needles, respectively. For these correctly identified needle diameters, the correct-to-incorrect ratios, regarding whether the needles were penetrating or not, were fitted with a probability of 0.5: (1) 0.14 mm: X2<0.001, p=1.00; (2) 0.16 mm: X2=0.03, p=0.86; (3) 0.18 mm: X2=2.00, p=0.16; and (4) 0.20 mm: X2=0.95, p=0.33.
Figure 2 shows the relationship between the clues the acupuncturist selected, the acupuncturist’s guesses, and the confidence of the guesses. Of the 320 needle insertions, 318 (99.4%) of the acupuncturists’ guesses were based on the feeling of insertion. For the needles guessed exclusively using the feeling of insertion (86.6%), no significant differences were observed in the acupuncturist’s confidence score between incorrectly guessed (49.1%) of and correctly guessed (37.2%) needles (p=0.25).
Figure 2.
Percentage of 320 needles and the mean score of confidence in acupuncturist’s guesses associated with the clues.
DISCUSSION
We investigated whether the results for acupuncturist blinding were influenced by insertion of needles of different DBN diameters, from 0.14 to 0.20 mm. The numbers of correct and incorrect guesses of DBN types weren’t significantly different with the different sizes of needles inserted. Also, random guesses, based on the BI for every diameter of needle, were a result of the efficacy of the acupuncturist’s blinding.
In the current study, almost all of the needles were identified based on the feeling of insertion and more than half of them were identified incorrectly. This result indicates that the stuffing in the guide tube provided enough resistance to the needle body during needle insertion for needles with 0.14, 0.16, 0.18, and 0.20 mm diameters.
The insertional force comprises 3 components that act on the needle: the tip force, the friction force, and the clamping force.19 The tip force acting on the needle tip in the axial direction is assumed to be primarily related to cutting the skin.19 The shape and size of the tips of needles with the 4 common diameters are almost the same; thus the tip forces for the needles may be similar. On the other hand, friction and clamping forces, which are generated by the viscoelastic properties exerted by the tissue on the sidewall of the needle body during insertion,15,20 may be different in those 4 sizes of needles because the surface area of each needle is different. This difference may become evident when the penetrating needle travels through multiple areas of tissue that have various viscoelastic properties. However, the current result provides evidence that possible increases in the needle insertional force with increasing needle diameters in conjunction with the needle body traveling through the tissue, didn’t significantly affect or break the acupuncturist’s blinding.
Even though the acupuncturist was able to see and feel the needle body during the needle insertions, it was difficult for her to discern small differences in needle diameter, especially for a difference of 0.02 mm. Most of the incorrectly identified needle diameters were ± 0.02 mm and 0.04 mm from the actual needle size. Therefore, it’s possible to blind acupuncturists regarding needle diameters within a range of ± 0.04 mm difference.
Uehara et al reinforced the idea that 0.16-mm needles are preferred among Japanese acupuncturists, followed by 0.18-mm needles.9
Studies need to be performed to determine whether a different dose effect occurs with needles of different diameters, especially with the 0.16 and 0.18 mm. We believe that the results of the current study warrant double blinding using DBNs in future dose studies.
Although no significant differences existed in confidence scores between the correct and incorrect guesses when the acupuncturist used only one clue, overall the acupuncturist’s confidence in correct guesses was higher than with incorrect guesses. The acupuncturist’s high confidence in her needle-insertion guesses occurred when she was using multiple clues, especially regarding the participants’ body movement and the feeling of the needle insertion. Participants’ movements associated with pain from the needle insertion resulted in the acupuncturist’s high confidence in her guesses. Therefore, controlling participants’ body movements is necessary for preserving the effectiveness of acupuncturist blinding in acupuncture clinical studies using DBNs.
Also, the current study used only penetrating needles. Non-penetrating needles weren’t used because the tip and needle body of the double-blind non-penetrating needles pass through the stuffing in the guide tube but aren’t inserted into the body. Thus, the non-penetrating needle doesn’t generate the same insertional-force changes that occur during insertion of a penetrating needle into the body. Studies using double-blind non-penetrating needles are likely to more easily blind the acupuncturist compared to the double-blind penetrating needles, which may allow more clues for guessing the needle type, because only penetrating needles are subject to insertional forces.
Limitations
This study has some limitations. Only penetrating DBNs were used, which may have influenced the results. Also, only one acupuncturist participated, and she used 0.16 or 0.18 mm diameter needles in her daily clinical practice. If the study’s acupuncturist were unfamiliar with the needle diameters used, however, the results may have been different.
CONCLUSIONS
The acupuncturist was unable to distinguish whether she inserted penetrating or non-penetrating DBNs, irrespective of their diameter—0.14, 0.16, 0.18, or 0.20 mm. Therefore, the acupuncturist remained blind to needle type. Future studies should include examining the ability of the participants to remain blinded to DBN type.
Acknowledgments:
Hiroyoshi Yajima, Miho Takayama, and Nobuari Takakura are supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant numbers JP15K08938, JP16K09266 and JP17K09329), Japan. This article was made possible by Grant Number R01HD091210 from the National Institute of Child Health and Human Development (NICHD), National Institutes of Health. Its contents are solely the responsibility of the authors and don’t necessarily represent the official views of the NICHD. The final peer-reviewed manuscript is subject to the National Institutes of Health Public Access Policy.
Authors’ disclosure statement:
For the needles described in this article, Takakura N and the Educational Foundation of Hanada Gakuen possess the following patents: US patent 6575992B1; Canadian patent CA 2339223; Korean patent 0478177; Chinese Taiwan patent 150135; Chinese patent ZL00800894.9, with the title “Safe needle, placebo needle, and needle set for double-blinding”; and 2 Japanese patents: patent 4061397, with the title “Placebo needle and needle set for double-blinding” and patent 4315353, the title “Safe needle.” Takakura N is a salaried employee of the Educational Foundation of Hanada Gakuen. Dr. Schlaeger received a grant from the National Institute of Nursing Research of the National Institutes of Health. No other author had any competing interests.
Contributor Information
Hiroyoshi Yajima, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan.;.
Miho Takayama, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan.;.
Morihiro Nasu, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan.;.
Masako Nishiwaki, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan.;.
Akiko Kawase, Japan School of Acupuncture, Moxibustion, and Physiotherapy, Tokyo, Japan..
You Hiramatsu, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan. The School of Graduate student of The Open University of Japan;.
Ruka Nobe, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan..
Judith M. Schlaeger, College of Nursing, Department of Women, Children, and Family Health Science, University of Illinois Chicago, Chicago, Illinois, USA..
Nobuari Takakura, Department of Acupuncture and Moxibustion, Faculty of Health Sciences, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan..
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