Acupuncture sensations are considered essential in producing the treatment effect of acupuncture. The Massachusetts General Hospital Acupuncture Sensation Scale (MASS) is a frequently used scale in acupuncture research to measure acupuncture sensations. We translated the MASS into Japanese (Japanese MASS) based on Beaton’s guidelines. 30 acupuncturists evaluated the relevancy and meaning of the 12 descriptors included in the Japanese MASS. The content validity ratios for 10 of the 12 descriptors were 0.33 or greater. 42 healthy subjects then evaluated acupuncture sensations evoked by manual acupuncture at LI4 using the Japanese MASS. Cronbach’s alpha was 0.86. The correlation coefficient of total MASS scores and total Short Form McGill Pain Questionnaire scores and MASS indices and sensory visual analogue scores were 0.78 and 0.80, respectively. Factor analysis loaded the 12 descriptors onto two meaningful factors. This study demonstrated that the Japanese MASS has good reliability, content validity, criterion-related validity, and construct validity. Therefore, the Japanese MASS is a valid and reliable instrument for use with Japanese populations.
Acupuncture sensations, or de qi, felt by patients are sensations elicited with needling and are traditionally considered to play an important role in acupuncture treatment [
Studies suggest that there are close associations between acupuncture sensations and acupoints [
The Acupuncture Sensation Scale (ASS) [
In order to use these acupuncture sensation scales to investigate patients’ acupuncture sensations in languages other than English, the scales must be translated into the respective language. The ASS, MASS, and SNSQ have been translated into Korean [
However, only the ASS has been translated into Japanese, with the descriptors adopted from the Japanese version of the MPQ [
In this study we aimed to develop a Japanese language version of the MASS, the English version of which is the most used sensation scale in acupuncture studies [
This cross-cultural adaptation of the MASS from English to Japanese comprised translation (Beaton’s stages 1–4) and validation and reliability tests (Beaton’s stage 5) [
The original English version of the MASS was translated into Japanese according to a five-step process for cross-cultural adaptation, as described by Beaton et al. [
In the first stage, two acupuncture researchers whose native language was Japanese made forward translations from English to Japanese. In the second stage, the two independent translations made by the acupuncture researchers were synthesised into a Japanese version (synthesised version), based on a discussion between the two translators. In the third stage, two native-born Americans whose native language was English produced two English backtranslations of the synthesised version. One backtranslator was an acupuncturist. The other was not an acupuncturist and had no medical/acupuncture background and no prior knowledge of or information about the MASS. In the fourth stage, an expert committee comprised of three licensed acupuncturists (all of whom held doctoral degrees in medicine) from the TAU Department of Acupuncture and Moxibustion, along with a Boston-based Japanese acupuncturist who had obtained her acupuncture license in Massachusetts, reviewed the original MASS, the forward translations, the synthesised version, and the two backtranslations. They discussed the material for semantic, idiomatic, experimental, and conceptual equivalences between the original MASS and the synthesised version to develop a prefinal version of the Japanese MASS.
In the fifth stage, we recruited 30 licensed acupuncturists (19 males, 11 females) to evaluate the content validity of the Japanese MASS, based on Lawshe’s approach [
We recruited 42 healthy subjects (20 males, 22 females, aged
Subjects lay on their back on a bed with their arms resting along their sides. An acupuncturist disinfected the subject’s skin with ethanol, administered the needle using the tapping-in method to penetrate the skin, and then applied the rotation technique at LI4 (large-intestine meridian) [
To exclude bias from acupuncture naïve or nonnaïve subjects, we randomly assigned acupuncture-experienced and non-acupuncture-experienced subjects to right LI4 or left LI4 groups using a web-generated table of random numbers (
Immediately after the removal of the needle, subjects completed three questionnaires on their acupuncture sensations during the needle rotation: (1) the sensory visual analogue scale (S-VAS), on which subjects rated the intensity of sensations from 0 (no sensation) to 100 (most severe sensation, unbearable); (2) the Japanese MASS (prefinal version), on which subjects rated the magnitude of each acupuncture sensation corresponding to the 12 descriptors on a numerical rating scale (NRS) from 0 (none) to 10 (strongest imaginable); if the subjects felt other sensations besides the 12 descriptors, they described the additional sensation and rated it on the NRS; (3) the Japanese version of the Short Form MPQ (SF-MPQ), which consists of the same sensory and affective descriptors as the original English version of the SF-MPQ. As the reliability of the Japanese SF-MPQ has been demonstrated, it may be used to evaluate criterion-related validity to show the concurrent validity of the Japanese MASS.
To evaluate the need for each descriptor as an acupuncture sensation and the content validity of the Japanese MASS, we calculated the content validity ratio (CVR) from the scores of all 30 acupuncturists using the formula used by Lawshe [
To estimate the reliability of the Japanese MASS, we calculated the Cronbach’s alpha coefficient using the scores obtained from all subjects to assess internal consistency. To evaluate the criterion-related validity to show concurrent validity, we calculated Pearson’s correlation coefficients between the total MASS scores and S-VAS scores, total SF-MPQ scores, and the sensory and affective dimension scores in SF-MPQ, respectively. We also calculated Pearson’s correlation coefficients between the MASS indices and the same scores. The MASS index is an exponential smoothing average, which is considered a more reliable method to measure the magnitude of overall acupuncture sensations than total MASS scores. We calculated the MASS indices using scores for the 12 descriptors [
Based on the original MASS study [
Statistical analyses were performed with SPSS Version 24 (SPSS Japan Inc., IBM Company, Tokyo, Japan).
Figure
Japanese MASS. Each descriptor in English is as follows: (1) soreness, (2) aching, (3) deep pressure, (4) heaviness, (5) fullness/distension, (6) tingling, (7) numbness, (8) sharp pain, (9) dull pain, (10) warmth, (11) cold, (12) throbbing, and (13) other. Intensities under each scale in Japanese (in English) are as follows:
Figure
Rate of responses for each descriptor (acupuncture sensation) and content validity ratios (CVR,
The mean ± SD intensity of acupuncture sensations marked on the S-VAS by the 42 subjects was
For the 42 subjects, the mean ± SD intensity for the total MASS score was
Frequency and intensity of acupuncture sensations on the Japanese MASS
In terms of the frequency of occurrence, “tingling” was felt by 70% of subjects, showing the highest occurrence of the 12 descriptors. Less than 5% of subjects felt “cold.” The frequencies and intensities of the sensations for the 12 descriptors were positively correlated; that is, the more frequent the occurrence, the higher the intensity (Figure
There were no significant differences between males and females, or between right and left LI4 for the S-VAS scores, total MASS scores, and MASS indices.
Overall, Cronbach’s alpha coefficient for the 12 descriptors was 0.860. The largest value for 11 descriptors was 0.865 with the exclusion of “cold,” the second largest was 0.856 with the exclusion of “soreness,” and the smallest was 0.835 with the exclusion of “warmth.” The corrected item-total correlation for “cold” was 0.154, while the others ranged from 0.427 to 0.734.
Total MASS scores and MASS indices correlated significantly with total SF-MPQ scores, S-VAS scores, and SF-MPQ sensory dimension scores. The Pearson’s correlation coefficient between total MASS scores and SF-MPQ affective dimension scores was larger than that between MASS indices and affective dimension scores (Table
Pearson’s correlation coefficients between total MASS scores and MASS indices versus SF-MPQ total scores, sensory dimension scores, affective dimension scores, and S-VAS scores
Total SF-MPQ scores | SF-MPQ sensory dimension scores | SF-MPQ affective dimension scores | S-VAS scores | |
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Total MASS scores |
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MASS indices |
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The factor analysis using a scree plot criterion loaded the 12 descriptors onto two factors. The cumulative contribution ratio was 0.561. The Kaiser-Meyer-Olkin statistic, which indicates sampling adequacy, was 0.796, and Bartlett’s test of sphericity was
Factor loadings of the Japanese MASS: two factors
Descriptors | Factors | |
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Varying pain sensation | Pressure sensation depth under the skin | |
Throbbing | 0.766 | |
Numbness | 0.722 | |
Aching | 0.668 | |
Cold | 0.648 | |
Sharp pain | 0.632 | |
Tingling | 0.596 | |
Dull pain | 0.555 | 0.451 |
Heaviness | 0.793 | |
Deep pressure | 0.764 | |
Soreness | 0.723 | |
Warmth | 0.474 | 0.651 |
Fullness/distension | 0.612 |
Note: factor loadings over 0.45 are exclusively represented.
The original English MASS was translated into Japanese to develop a reliable and valid Japanese MASS for use in evaluating acupuncture sensations, or de qi, in acupuncture trials with Japanese populations. The results obtained from our reliability and validation tests showed that the Japanese MASS is a reliable and valid questionnaire to evaluate acupuncture sensations associated with needle insertion or manipulation in a Japanese sample. Our study yielded the first reliable and valid Japanese version of the MASS.
In the Oxford English Dictionary, “soreness” is defined as “a raw or painful place on the body.” Translating “soreness” into “feeling of languid” in Japanese might have been biased due to the translator’s previous experience with acupuncture. However, this biased translation was highlighted in the backtranslation and amended by the expert committee. There was no discrepancy between the two backtranslators in the backtranslation process, even though one backtranslator had a medical/acupuncture background, which is not consistent with Beaton’s guidelines. This suggests that the backtranslation process avoided information bias and elicited no unexpected meanings for the descriptors. Given the amendment of the initial forward translation of “soreness” in the third and fourth stages of our cross-cultural adaptation process, we believe that the meanings of the descriptors in the Japanese MASS are equivalent to those in the English MASS.
A relatively large proportion of acupuncturists in our study disagreed with “cold” being an acupuncture sensation, which might be because patients and subjects rarely reported a “cold” sensation during needling. In the original and Chinese MASS study, “cold” was included because coldness and warmth are two of the earliest sensations to be symptom-specific based on the vacuity-repletion theory [
The CVR for “fullness/distension” was lower than that for “cold.” However, we found the average intensity and frequency of “fullness/distension” were higher than those of “cold”; therefore, we kept the descriptor in the MASS.
The overall Cronbach’s alpha coefficient for the descriptors (0.860) was between 0.70 and 0.95, indicating that the Japanese MASS had good internal consistency [
The criterion-related validity of the Japanese MASS was demonstrated by strong correlations between total MASS scores and total SF-MPQ scores and between total MASS scores and the SF-MPQ sensory dimension scores. These strong correlations were expected, as four descriptors classified as sensory from the SF-MPQ are included in the MASS, and the descriptors in the ASS are closely related to those in the MPQ [
The SF-MPQ affective dimension scores were moderately correlated with the total Japanese MASS scores, whereas no correlation was found with the Chinese MASS [
The stronger correlation between the S-VAS scores and the MASS indices than between the S-VAS scores and total MASS scores indicates that the Japanese MASS indices expressed the total amount of acupuncture sensations well. Therefore, the Japanese MASS works as well as the original MASS in studying acupuncture sensations.
Although the 12 descriptors were classified into five factors in the Chinese MASS validation study, they were classified into two meaningful factors in the Japanese MASS, which corresponded to the two factors in the original MASS [
The Japanese MASS presented in this study will allow Japanese acupuncture researchers to investigate acupuncture sensations in clinical studies with Japanese populations. In order to understand acupuncture sensations in terms of clinical efficacy from an ethnical perspective, further exploration is necessary to compare the de qi profiles in the Japanese MASS with those obtained by the original MASS and the Chinese MASS.
Our study demonstrated that the Japanese MASS has good reliability, content validity, criterion-related validity, and construct validity. Therefore, the Japanese MASS is a valid and reliable instrument for use with Japanese populations.
The authors declare that they have no conflicts of interest.
The authors express their appreciation to all participants of this study, especially the translators. Jian Kong is supported by R01AT006364, R01 AT008563, R21AT008707, R61AT009310, and P01 AT006663 from NIH/NCCIH. They also thank Joel Park and Courtney Lang at Massachusetts General Hospital for their help in polishing English.