Blinding Effectiveness of Sham Acupuncture Devices
Overall Blinding Effectiveness of Sham Acupuncture Devices
When conducting acupuncture clinical trials, subjects from both real acupuncture group and sham acupuncture group should believe that they receive real acupuncture to mimic the actual scenario which takes place during acupuncture treatment. As shown in Fig. 5, the existing non-penetrating sham acupuncture devices such as Park, Streitberger, Takakura, foam and cocktail stick displayed a result which favoured the sham group and was also statistically significant. In other words, more participants in the sham acupuncture group who did not identify the sham acupuncture treatment correctly compared to the real group and hence, they were blinded. As a result, non-penetrating sham acupuncture devices can act as an effective placebo control method to be applied in acupuncture clinical trials, especially in replacing other less effective types of control methods such as using no treatment, standard/conventional treatment or skin-penetrating sham acupuncture as the control.
Comparison between Sham Acupuncture Devices
Among all the non-penetrating sham acupuncture devices included in the data analysis, the foam device demonstrated the best ability in achieving the blinding of participants. There were five studies10,47,50,51,56 which used the foam device in their control group. The foam device is usually self-prepared by the researchers, so there are some variations in design. It is made out of a certain thickness of foam with double-sided adhesive tape at the bottom (Fig. 10). The foam pad can act as a supportive material to hold the needle in place even in the placebo group, whereas the adhesive tape can stick the device on the skin. The real foam device utilises a real acupuncture needle with a sharp tip which can penetrate the skin of participants; the placebo foam device uses a shorter blunted acupuncture needle which cannot penetrate the skin. Ultimately, the appearance after needle insertion will remain the same and hence, achieve blinding of participants in terms of vision. After needle insertion, the real device will penetrate the skin with a certain depth, whereas the placebo device will only touch the skin to blind the participants by mimicking the feeling of penetration. In the studies of Fink50 and Goddard51, the placebo needles were gently twisted to enhance the feeling of penetration. Besides having a good blinding effect, the foam device is also less pricey and easily accessible compared to the other devices, so it can be a good option to be used in the control group of acupuncture clinical trials. However, owing to the preparation of the foam device is usually self-made, hygiene in preparing the device will become the main concern. All the equipment must be sterilised adequately before being applied to the participants.
The other sham acupuncture devices such as Streitberger, Park and Takakura (Fig. 11) are also effective in blinding the participants. Their sham devices look identical with the real devices. Similar to the foam device, their sham devices possess shorter blunted-tip needles which touch on the skin to mimic penetrating sensation. Hence, all of them can be applied in clinical trials. The characteristics of the foam, Streitberger, Park and Takakura devices have been summarised in Table 3. On the other hand, the sham device of no-touch Takakura was not statistically significantly superior to the real device (P = 0.19), so it is not recommended to be used in clinical trials. No-touch sham Takakura device has no contact with the skin of participants. It may be useful in achieving visual blinding but not tactile blinding.
Table 3
Analysis of Sham Acupuncture Devices
Devices
|
Characteristics
|
Price75
|
Advantages
|
Limitations
|
Foam
|
Needle is supported by an opaque guide tube which is attached to the foam base; adhesive tape at the bottom
|
N/A
|
Inexpensive, easily accessible and self-prepared
|
Potential risk of hygienic issue and inconsistency of quality of the foam
|
Streitberger
|
Sham: retractable needle supported by plastic ring covered with plastic sheet as the base; adhesive tape at the bottom
|
$6.3 per needle
|
Can insert in different angles
|
Sham needle attachment is not firm
|
Park
|
Needle is supported by an opaque guide tube and a Park tube which is connected with the ring base; adhesive tape at the bottom
|
$2.9 per needle
|
Able to perform simple needle manipulations
|
Can only insert perpendicularly
|
Takakura
|
Needle is supported by an opaque guide tube which is filled up with stuffings at upper and lower ends and the tube is connected to an adhesive pedestal
|
N/A
|
Potentially blind the acupuncturist
|
Can only insert perpendicularly
|
N/A: not available |
Notes: price was cited from the other article. Current price may differ from the past time. |
In short, each sham acupuncture design has its own advantages and limitations. Researchers should take that into consideration when designing the experimental and control methods. Due to high heterogeneity of the studies across the subgroups (Fig. 6), the OR value may be influenced by other factors and hence, the results of blinding effectiveness of sham devices can only serve as a reference.
Limitations of the Existing Sham Acupuncture Devices
The limitations of the existing sham acupuncture devices can be discussed in several aspects, including the suitability in performing electro-acupuncture, needling location, needling angle and blinding effect in acupuncturists.
The sham devices of foam, Streitberger, Park and Takakura solely rely on the adhesive double-sided tape or pedestal to attach to the skin. The attachment is not as firmly as those in the real acupuncture, therefore, sham electro-acupuncture is difficult to perform by using these devices. Moreover, the adhesive tape may not be suitable for hairy skin or areas which are not flat. As a result, using sham acupuncture devices on the scalp, hairy regions and the skin with a great curvature such as the ears, fingers and toes can be challenging.
Apart from that, needling angle is usually limited to perpendicular for the foam, Park and Takakura devices due to the presence of guide tube, so only acupoints that allow perpendicular insertion can be selected when using these devices. Acupoints such as LU7 LieQue and EX-HN3 YinTang or acupoints on the scalp which require oblique or transverse insertion cannot be chosen in the trials. On the contrary, Streitberger device, which does not have a guide tube, can perform perpendicular and oblique insertions. Yet, having no guide tube can also make the needle unstable especially in the sham group, increasing the risk of exposure of grouping allocation.
Last but not least, most of the sham acupuncture devices did not demonstrate the ability to blind acupuncturists, except for the Takakura device. The Takakura device has added a lower stuffing within its guide tube to mimic the feeling of skin penetration when the acupuncturist pushes the sham needle into the lower stuffing. In other words, the performance bias will be high in the acupuncture clinical trials that use other types of sham acupuncture devices.
Considerations of Designing Sham Acupuncture Controlled Clinical Trials
Guidelines of Sham Acupuncture Controlled Clinical Trials
In 1995, the Guidelines for Clinical Research on Acupuncture4 by the WHO stated that placebo acupuncture should fulfil two criteria: it must be a less effective form of acupuncture and also mimic acupuncture in a credible manner. Zhang’s paper76 also stated that placebo acupuncture should have no or minimal specific treatment effects on the tested disease and the treatment and control groups should be identical to achieve blinding. To evaluate the true efficacy of acupuncture, the difference in specific effects shall be maximised but the difference in non-specific effects shall be minimised (Fig. 12).
Determining a research question is important before selecting the type of control because each control method can be used to answer different types of research questions. As shown in Table 4, no treatment and standard treatment as control can rule out regression to the mean and study the general effectiveness of acupuncture; non-penetrating sham as control can rule out regression to the mean and psychological responses (placebo effect) and study the efficacy of acupuncture, including skin-penetrating physiological effects and acupoint specific effects; lastly, penetrating sham as control can rule out three other aspects and study specifically on the efficacy of acupoint specific effects77,78. As far as the authors know, non-penetrating sham acupuncture is the only method that can eliminate the placebo effect and meanwhile, minimise the physiological responses being generated. So, it can be widely used in a broad range of acupuncture clinical trials that study the specific effects of acupuncture. On the other hand, penetrating sham acupuncture (e.g. shallow needling/minimal acupuncture and needling on non-acupoints) is suitable to study narrower specific effects of acupuncture that will not be generated by skin penetration. Do note that the acupuncturists of penetrating sham acupuncture are not blinded most of the time owing to different needling techniques and locations in the sham group and hence, it may lead to performance bias of personnel. In addition, it has to be ensured that skin penetration will not trigger any desired specific effects of the study, if not it will result in no significant difference in both arms.
Table 4
Study Focus of Different Types of Acupuncture Control
Types of Control
|
Aspects
|
Regression to the Mean
|
Psychological Responses
|
Physiological Responses*
|
Acupoint Specific Effects
|
No treatment
|
X
|
Effectiveness
|
Efficacy
|
Efficacy
|
Standard treatment
|
X
|
Effectiveness
|
Efficacy
|
Efficacy
|
Non-penetrating sham
|
X
|
X
|
Efficacy
|
Efficacy
|
Penetrating sham
|
X
|
X
|
X
|
Efficacy
|
*, physiological responses caused by the skin penetration |
Note: the boxes with “X” in Table 4 indicate the areas that are eliminated when comparing with the real acupuncture group. |
Factors which May Influence the Blinding Effectiveness of Sham Acupuncture Devices
Besides the selection of sham acupuncture method and device, there are other factors which may also play a role in achieving successful blinding, for example, acupuncture experience and health status of the participants and needling location. As shown in Fig. 7, the naive participants are more easily blinded than the experienced participants. The experienced participants are more familiar with the acupuncture process and DeQi (needling) sensation and hence, they are more likely to guess the grouping accurately. However, both groups showed a significant difference in blinding effectiveness. Ideally, naive subjects should be recruited in acupuncture clinical trials, but experienced participants can also be considered if naive ones are not available or sufficient.
Next, both healthy and diseased participants demonstrated a significant difference in blinding effectiveness, in which the healthy ones were slightly superior to the other group (Fig. 8). Healthy subjects should be prioritised when designing acupuncture clinical trials, nonetheless, recruiting diseased participants is unavoidable when studying the efficacy of acupuncture on a particular disease.
Lastly, the locations of acupoints may also influence the effectiveness of blinding. As shown in Fig. 9, the OR values of the abdomen (11.33) [0.71, 180.77] and the back (9.1) [3.14, 26.36] were higher compared to the upper limbs (4.31) [2.50, 7.43] and the lower limbs (3.69) [0.82, 16.62]. This phenomenon is associated with the higher sensitivity of the skin and stronger needling sensations in the four limbs due to rich nervous distribution. Yet, only the back and upper limbs showed statistically significant different P-values.
Limitations of the Study
Four studies had been excluded due to language barrier and seven studies had been excluded due to inaccessibility of the full-text articles. Excluding articles other than English and Chinese may introduce language bias. Excluding inaccessible articles may also reduce the precision of combined estimates of blinding effectiveness. However, the authors were not able to overcome it due to limited resources. The included studies utilised different ways to present data, so some data had to be converted before performing the meta-analysis. Also, some studies presented their results in terms of the number of participants, whereas some were based on the total responses from the participants.
A variety of study designs also led to high heterogeneity in the results of the meta-analysis. Other potential influencing factors which might contribute to the heterogeneity such as the diameter of acupuncture needle, the depth of needle insertion, the duration of needle retention, needle manipulation techniques and the number of treatments were not analysed in the study. For instance, the participants may be aware of the grouping by observing the procedure and treatment effects after having multiple and long-time treatment.
The number of articles in some of the subgroups was small. For example, Kim device and cocktail stick device in the analysis of the types of sham acupuncture devices possessed solely one study; besides, the head and neck, abdomen and lower limbs in the analysis of the locations of acupoints possessed a small number of studies.