Pressure Probes for Auriculotherapy Diagnosis: Are They Accurate?

Abstract

Background:

Point detection is a pillar for auriculotherapy diagnosis. However, the pressure probes’ accuracy is yet to be established.

Objective:

To assess the accuracy of commercially available pressure probes for auriculotherapy’s diagnosis.

Methods:

Four probes were tested against a semi-analytic bubble level and calibrated precision pressure scale. Forty peaks of pressure from each device were recorded. The raw and the normalized peaks (by probes’ length and diameter) were analyzed.

Results:

The absolute and the relative trials consistency were considered reliable, but inter-device differences were found for all pairwise comparisons among devices. The ideal preset pressure of 250 g was not achieved by any device, with effect sizes ranging from moderate to huge.

Conclusions:

All devices showed higher values compared with 250 g. The device’s results disagree compared to each other, impairing the reliability and the diagnosis. Aside from the within-device absolute and relative consistency, the results suggest there is still no gold-standard device to assertively assess the auricular tender points.

INTRODUCTION

Auriculotherapy consists of stimulating the external ear to modulate the central nervous system’s plasticity.^1–3 During the decade of 1950, Dr. Paul Nogier proposed the theory of somatotopic representation, where body regions are represented on the external ear.^4,5 This theory would allow the treatment of a disorder from a particular part of the body using the corresponding point or area in the ear.⁶

Auricular point detection is a pillar to diagnose areas that must be treated by auriculotherapy.^7,8 Pressure-probes are often used to provoke pain in the affected areas, identifying pressure pain thresholds (PPTs) according to the patient’s perception.^7,9 Once the probe is perpendicularly positioned on the point, the built-in spring mechanism is supposed to deliver around 250 g of pressure to evoke pain on the sensitized location.⁷ Thus, the auriculotherapist may diagnose and treat the affected area using distinct types of stimuli (for example, needle, electric, or laser).^10–12

Screening the pressure-probes’ parts and mechanism, the inner spring’s tension may account for the level of applied pressure, and its calibration might affect the reliability of successive measures. Aside of that, the terminal end of the probe that contacts the patient’s skin may also interfere due to the probe’s length until the spring is fully inserted or also due to a reduced area of contact with the patient’s skin.

Any device used for diagnostic purposes must provide enough accuracy to guide the treatment’s prescription.¹³ However, and despite the widely accepted validity of those devices as well as their manufacturer’s calibration assurance, to our knowledge, no evidence was found to ensure the results obtained from the commercially available pressure-probes. Thus, the present study aimed to test the accuracy of four commercially available pressure-probes for auricular diagnostic.

METHODS

Experimental Set-up and Procedures

Four pressure probes (Table 1 and Fig. 1) were tested against a semi-analytic bubble levelled and calibrated precision pressure scale (Bioscale, Varzea, Portugal, Model BL 1200AS-BI, maximum load = 1200 g, d = 0.01 g; Fig. 2). A single experienced rater randomly positioned each pressure-probe on the center of the scale plate. Then, four sets of 10 pressure trials for each pressure-probe were performed (1 min of rest between sets was allowed). The vertical pressure was exerted until the contact probe was completely inside of the tested device’s body, by pressuring the inner spring. To avoid any additional pressure bias, no contact between the edge of the device’s body and the scale plate was allowed. The scale display was continuously recorded using high-resolution smartphone’s camera (Redmi Note 8 Pro, Xiaomi, Beijing, China, 4K, 30 fps). All recorded videos were uploaded to Kinovea software (version 0.9.5, retrieved from: http://www.kinovea.org). As the pressure increased, the frame-by-frame video analysis was performed to report the actual pressure peak from each trial. Data were extracted to Excel (Microsoft Corporation, 2018; Redmond, WA, US, USA; Available at: https://office.microsoft.com/excel). All trials were performed in the Biochemistry Laboratory of the Federal University of Juiz de Fora, Brazil.

Table 1.

Pressure-Probes’ Characteristics. A Calibrated Digital Caliper (WorldTools-MTX, Limeira, SP) Was Used to Assess the Probes’ Diameter and Length

Manufacturer	Probe diameter	Probe length
Sedatelec (Irigny, France)	2.02 mm	14.76 mm
Fava (Barreto, Brazil)	2.37 mm	21.91 mm
Dux (Porto Alegre, Brazil)	1.97 mm	12.36 mm
Complementar (São João Del Rei, Brazil)	2.61 mm	21.90 mm

FIG. 1.

Pressure probes. (A) Sedatelec; (B) Fava; (C) Dux; (D) Complementar.

FIG. 2.

Semi-analytic precision scale.

Statistical Analysis

Data were expressed as mean and standard deviation. The outcome variables were defined as the raw pressure values, the ratio between the obtained pressure values and the probe’s length, and the ratio between the pressure values and the probes’ diameter (normalizing factors). The absolute between-trials reliability was assessed using the coefficient of variation calculated by the ratio of the standard deviation to the mean multiplied by 100 to be expressed in percentage coefficient of variation (%CV). The optimal %CV return values are less than 10%. The intraclass correlation coefficient (ICC) along with the Cronbach’s α coefficient was used to assess the consistency among all trials. ICC and Cronbach’s α values were qualitatively classified as poor (<0.50), moderate (0.5–0.75), good (0.75–0.90), or excellent (>0.90).¹⁴ The one-way analysis of variance (ANOVA) was used to detect the inter-device differences. The Bonferroni’s post hoc test was used to avoid multiple testing during pairwise comparisons. The Cohen’s d coefficient (ES) was used to assess the magnitude of the effect size. The magnitude of the ES was qualitatively interpreted using the following thresholds: <0.2, trivial; 0.2–0.6, small; 0.6–1.2, moderate; 1.2–2.0, large; 2.0–4.0, very large; and >4.0, huge.¹⁵ In addition, the one-sample t-test was used to understand the extent of the differences compared with the ideal 250-g preestablished value. All data analysis was performed using the JAMOVI software (v. 1.6.15.0, The JAMOVI Project, 2022), with the significance level set at 5%.

RESULTS

The absolute pressure was progressively recorded from the pressure-probes of Fava (mean = 331 g [SD = 11.37 g]), followed by Sedatelec (346.56 g [13.20 g]), Complementar (404.64 g [6.68 g]), and Dux (449.60 g [16.76 g]). The normalized values are in the Table 2. The %CV was considered low for all devices (Sedatelec = 3.81%, Fava = 3.44%, Dux = 3.73%, and Complementar = 2.15%), and they were not affected by the normalization procedure. The trial’s consistency was classified as excellent (ICC = 0.97 and Cronbach’s α = 0.99).

Table 2.

Normalized Pressure Values

Device	Diameter-normalized (in g/mm)	Length-normalized (in g/mm)	Differences
Sedatelec	171.56 (6.54)	23.48 (0.89)	Dux > Sedatelec > Complementar > Fava^*
Fava	139.68 (4.80)	15.11 (0.52)
Dux	228.22 (8.51)	36.38 (1.36)
Complementar	155.04 (3.33)	18.48 (0.40)

All pairwise comparisons: p < 0.001.

Considering the raw values, differences were found for all comparisons with moderate to huge ES (F = 928, p = 0.001; Sedatelec vs. Fava, p = 0.001, ES = 1.08 [moderate]; Sedatelec vs. Dux, p = 0.001, ES = 5.87 [huge]; Sedatelec vs. Complementar, p = 0.001, ES = 3.81 [very large]; Fava vs. Dux, p = 0.001, ES = 7.43 [huge]; Fava vs. Complementar, p = 0.001, ES = 5.27 [huge]; Dux vs. Complementar, p = 0.001, ES = 2.42 [large]). The diameter and length-normalized values also showed significant differences (Table 2). When normalized, the main finding was the Complementar device delivering less pressure compared with the Sedatelec device. Other pairwise comparisons remained in the same order of the raw values. The diameter-normalized ES were from very large to huge (Sedatelec vs. Fava, ES = 5.22 [huge]; Sedatelec vs. Dux, ES = 9.28 [huge]; Sedatelec vs. Complementar, ES = 2.71 [very large]; Fava vs. Dux, ES = 14.50 [huge]; Fava vs. Complementar, ES = 2.51 [very large]; Dux vs. Complementar, ES = 11.98 [huge]). The length-normalized ES followed the same path, ranging from very large to huge (Sedatelec vs. Fava, ES = 9.57 [huge]; Sedatelec vs. Dux, ES = 14.74 [huge]; Sedatelec vs. Complementar, ES = 5.72 [huge]; Fava vs. Dux, ES = 24.30 [huge]; Fava vs. Complementar, ES = 3.85 [very large]; Dux vs. Complementar, ES = 24.46 [huge]).

The Fava device was the closest to the optimal pressure of 250 g, but still with significant differences and a huge ES (p = 0.001, ES = 7.13 [huge]). The 2nd was the Sedatelec (p = 0.001, ES = 7.31 [huge]), followed by Complementar (p = 0.001, ES = 11.91 [huge]) and Dux (p = 0.001, ES = 17.81 [huge]).

DISCUSSION

The results showed consistency among trials, but significant inter-device differences were observed. All devices were far from the optimal pressure of 250 g, and aside from the huge ES of them all, the Fava pressure probe showed the closest value, respectively, followed by Sedatelec, Complementar, and Dux devices.

Objective pain assessment is very important to establish a prospective evaluation, comparing baseline results to other timeline assessments or even as a prognostic measure that can predict future outcomes,^16,17 but for auriculotherapy, it is essential as the method is fully based on the detection of tender points. In this sense, excessive pressure delivered by the probe may lead to misdiagnosis and confusion to select the points to be treated. The point would elicit pain due to overpressure instead of tenderness in the area. Tenderness of acupuncture points could be explained by the accumulation of subdermal noxious substances,¹⁸ but evidence assessing the reliability of pressure diagnoses is conflicting. Without any information on the current medical condition, a study showed the capacity to correctly predict around 75% of actual medical diagnosis in 40 patients using the auricular diagnostic.¹⁸ Another study showed that combining inspection and palpation of auricular tender points, medical symptoms were accurately diagnosed in 78.6% of 506 patients.⁸ In addition, the authors found that an increased number of tender points in the specific auricular areas (upper part of the ear, lower part of the auricle, posterior transition zone between the ear lobe and antihelix/helix, anterior of the tragus, intertragic notch, and anterior part of the lobe) were correlated to the severity of pain. However, other reports account only 50–55% of accuracy for point detection using 250 g pressure-probes,⁷ suggesting a general pattern of autonomic changes that may occur in response to auricular stimuli, with variable intensity depending on the area of stimulation.¹⁹ The authors also found that the average pressure pain threshold for auricular detection was 468 g instead of the 250 g suggested by Nogier.⁶ They suggest using a set of probes, selecting distinct levels of pressure depending on the assessed area of the ear.

Another complex issue is the relationship between the diameter and the length of the probe with the pressure delivered by the system. The current measures showed a lack of consistency for those probes’ characteristics and also a lack of information on the manufacturer’s website and on the probes’ packages. As the auricular diagnostic accuracy lays on those parameters, it would be expected that standardization of the probes would already be achieved. An important upgrade for research would be an index considering the combined length and diameter effect on the applied pressure to normalize the results. However, the usefulness of such an index in clinical settings may be questioned, as the equipment used to assess the outcome must be already prepared to respond immediately to the applied stimuli to provide the diagnostic. Nevertheless, normalizing is usual in science. Raw electromyography values need to be normalized by the maximal isometric voluntary contraction to avoid heterogeneity.²⁰ Muscle strength measures are often normalized using the lever arm (the distance between the movement axis and the point of applied resistance).^21,22 Handgrip and pinch strength in older adults is often normalized by the subject’s weight.^23,24 When the normalization was performed, it affected the outcome pressure delivered by Sedatelec and Complementar devices. To avoid inconsistencies in group contrasts, further comparisons of studies effects (including reviews with or without meta-analysis) should describe the device brand in addition to its characteristics. A normalization procedure is also recommended. However, the standardization of the device’s characteristics for diagnosis is very encouraged. The accuracy on tangibility and the traceability of clinical results rely on it. If the standardization is not yet a reality, the same device should always be used for prospective comparisons.

Limitations and Future Directions

Some limitations of the present study must be addressed. The study was designed to assess the precision and the consistency of the selected pressure probes. Further studies may assess the reliability of distinct devices to assess in vivo point locations. Only four pressure probes were included, so the results are valid only for them. Other probes can show different results. However, the Sedatelec is the most recommended brand by the auriculotherapy internationally teaching, including the Groupe Lyonnais d’Études Médicales—GLEM, the original center of auriculotherapy in France. In other countries, it may vary and lead to misdiagnosis depending on the raw pressure on the ear. Some devices’ specifications, such as the spring tension, length, and hysteresis, were not described due to the lack of those by the manufacturer.

CONCLUSIONS

All tested devices showed statistically higher values compared with the preestablished ideal of 250 g. The ES were all higher than the expected amount for a standard assessment. Also, their results did not agree compared to each other, which may impair the reliability and the further auricular diagnostic. Aside from the within-device absolute and relative consistency, the results suggest there is still no gold-standard device to assertively assess the auricular reflex points.

Footnotes

ACKNOWLEDGMENTS

The authors thank the Department of Physical Therapy of the Federal University of Juiz de Fora.

DATA AVAILABILITY

The raw data were available online: Barbosa, Alexandre (2022), “Pressure probes for auriculotherapy diagnosis: are they accurate?”, Mendeley Data, V1, doi: 10.17632/cwkbwdh2cg.1

AUTHOR DISCLOSURE STATEMENT

The authors declare that they have no conflicts of interest.

FUNDING INFORMATION

No funding was received for this article.

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