Test-Retest Reliability and Criterion Validity of the Spanish Version of Two Motor Imagery Questionnaires in People With Parkinson Disease : Journal of Neurologic Physical Therapy

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Test-Retest Reliability and Criterion Validity of the Spanish Version of Two Motor Imagery Questionnaires in People With Parkinson Disease

Moreno-Verdú, Marcos PT, PhD; Ferreira-Sánchez, María del Rosario PT, PhD; Martín-Casas, Patricia PT, PhD; Atín-Arratibel, María de los Ángeles MD, PhD

Author Information
Journal of Neurologic Physical Therapy 47(1):p 35-43, January 2023. | DOI: 10.1097/NPT.0000000000000416

Abstract

INTRODUCTION

Mental practice with motor imagery (MI) has been widely and successfully used to improve motor performance in both sports1,2 and musical disciplines3 through the promotion of motor learning.4 However, evidence of its effectiveness on neurodegenerative diseases such as Parkinson disease (PD) is conflicting. Several studies have shown promising results with body schema,5 mobility, motor function,6 or gait speed7 improvements, whereas others have found no significant differences in comparison with relaxation8 or conventional physical therapy9 interventions. The ability of the person to perform MI has been identified as one of the possible factors that may influence the effectiveness of MI-based programs.10 Hence, assessing MI ability is relevant to efficiently implement these procedures in specifically suitable clinical groups that might benefit to a greater extent.

MI ability can be assessed with biological or behavioral procedures. Behavioral assessments evaluate specific domains of motor images such as temporal accuracy (ie, the time congruence between actual and imaged actions), controllability (ie, the ability to mentally manipulate images), or vividness (ie, the subjective intensity with which a person experiences MI). These aspects are assessed with separate tests such as mental chronometry, mental rotation, or questionnaires, respectively.11,12 Specifically, vividness questionnaires are widespread tools typically distinguishing between the 2 main sensory modalities used during imagery (ie, visual and kinesthetic).13 There are plenty of questionnaires currently available,14 but 2 of the most widely used in clinical contexts are the Kinesthetic and Visual Imagery Questionnaire (KVIQ) and the Movement Imagery Questionnaire-Revised Second Version (MIQ-RS), both specifically developed for people with sensory motor disabilities.15,16 Evidence of the validity of the English KVIQ in people with PD is available,17 whereas there is a lack of studies providing evidence of the validity and reliability of the MIQ-RS. These tools represent an inexpensive, fast, and useful procedure to detect poor or good imagers and therefore may optimize MI-based treatments by identifying who is more suitable to be trained with mental practice techniques and selecting therapeutic strategies based on performance.

Multiple transcultural adaptations and translations into several languages are now available for both questionnaires,18–21 as well as evidence of good psychometric properties in people with stroke or multiple sclerosis.15,22,23 Although the KVIQ has been used in people with PD,24–27 the usage of the MIQ-RS is much more limited because of a paucity of psychometric studies. Previous work consistently shows that both questionnaires have a 2-dimensional structure, therefore assessing visual or kinesthetic vividness separately.15,16,23 There is also evidence of excellent internal consistency (Cronbach α = 0.87-0.98), acceptable to moderate test-retest reliability (KVIQ: ICC = 0.81-0.9; MIQ-RS: ICC = 0.54-0.73) and good criterion validity between them.15,23 Nonetheless, their psychometric behavior remains largely unexamined in people with PD. No studies to date have analyzed the validity of the MIQ-RS in these people, though Randhawa et al17 assessed test-retest reliability of the English KVIQ and its criterion validity with the MIQ-R (first revised version) in a small sample of participants with mild to moderate PD (n = 11). However, they did not evaluate its factor structure or internal consistency, which should be previously examined according to current consensus-based standards.28 In addition, the MIQ-R includes difficult movements (eg, jumping) and thus is not the most appropriate questionnaire in people with sensory motor deficits, who should be evaluated with the MIQ-RS.29

Spanish translations of the MIQ-RS and the KVIQ are recently available, which allows to examine their appropriateness to evaluate MI ability in Spanish-speaking clinical populations.30,31 Therefore, the purpose of this study was to assess the psychometric properties of these 2 Spanish versions of the questionnaires in people with PD. We aimed to (1) assess structural validity to evaluate their 2-dimensional structure; (2) examine internal consistency and test-retest reliability of total and subscale scores individually, if pertinent; and (3) evaluate criterion validity by correlating their total and subscale scores.

METHODS

Study Design

This study followed the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) guidelines.28 A descriptive longitudinal study was conducted at the Madrid Parkinson Association. The study was approved by the Ethical Committee for Clinical Research of the Clínico San Carlos Hospital, and written informed consent from all participants was obtained prior to enrollment. All procedures were performed/done in accordance with the 1964 Declaration of Helsinki.

Participants

Sample Size Calculation

Sample size was calculated using previous models proposed for test-retest reliability studies using an asymmetrical interval procedure for not achieving a prespecified lower limit.32 The prespecified value (p0) was ICC ≤ 0.5 for unacceptable reliability,33 with a 95% probability of not obtaining that value. The expected value of ICC ≥ 0.8 was based on previous literature.17 Thirty-two participants were needed to reach a significance level of 0.05 and test power of 0.8, but considering a dropout rate of 10%, a total of 35 participants were required. This calculation was performed in Microsoft Excel 2016.

Selection Criteria

Participants were included if they (1) had a diagnosis of idiopathic PD (according to the United Kingdom Parkinson Disease Society Brain Bank Criteria),34 (2) were older than 60 years, and (3) were able to stand independently. Participants were excluded if there was evidence of (1) cognitive impairment (Mini-Mental State Examination score <24)35 or (2) a diagnosis of neurologic diseases other than PD, psychiatric diseases, orthopedic diseases, or cardiovascular diseases, or (3) the presence of visual sensory deficits (ie, complete blindness) or range-of-motion limitations (ie, <80% of age-adjusted active range of motion36 in joints involved in movements assessed with the questionnaires and measured with standard goniometry procedures37) that could interfere with the assessments.

Participants' Characteristics

Thirty-five people with a diagnosis of idiopathic PD (17 women, mean age = 74.2 years, SD = 7.2), with a mean disease duration of 8.8 years (SD = 5.9) and in Hoehn and Yahr stages I-IV participated. Impact of disease (Movement Disorders Society-Unified Parkinson's Disease Rating Scale [MDS-UPDRS]) and level of functional independence (Schwab & England scale) are shown in Table 1. According to MDS-UPDRS data,38 participants were subdivided into postural instability/gait difficulty (PIGD) (n = 25) and tremor dominant (TD) (n = 9) motor phenotypes of PD. One participant was classified as indeterminate. None of the participants had undergone deep brain stimulation surgery.

Table 1 - Functional Status of the Participants
Variable Category Mean Score SD
MDS-UPDRS Total 59.71 18.63
Part I 13.14 6.53
Part II 16.17 6.85
Part III 26.43 8.19
Part IV 3.97 3.34
n (%)
Motor phenotype TD 9 (25.71)
PIGD 25 (71.43)
Indeterminate 1 (2.9)
Hoehn and Yahr stage 1 1 (2.9)
1.5 5 (14.3)
2 5 (14.3)
2.5 8 (22.9)
3 13 (37.1)
4 3 (8.6)
Schwab & England scale 40% 1 (2.9)
60% 3 (8.6)
70% 4 (11.4)
80% 11 (31.4)
90% 15 (42.9)
100% 1 (2.9)
Abbreviations: MDS-UPDRS, Movement Disorders Society-Unified Parkinson's Disease Rating Scale; PD, Parkinson disease; PIGD, postural instability/gait difficulty; TD, tremor dominant.

Assessments

Spanish KVIQ Version

The KVIQ questionnaire evaluates MI vividness with a difference between visual and kinesthetic sensory modalities. It can be administered as the short (KVIQ-10), long (KVIQ-20), and extended (KVIQ-34) versions, which are additive.15 It evaluates simple movements of the neck, trunk, and upper and lower limbs. Limb items are administered unilaterally (short and long versions), on the dominant or nondominant side depending on the item, or bilaterally (extended version). Each item involves 4 steps: (1) adopting an initial position; (2) physically performing a movement; (3) returning to the initial position; and (4) visually or kinesthetically imaging that movement. After that, the participant rates the intensity perceived during the mental task on a 5-point scale, from 1 = no image to 5 = image as clear as actually seeing it (visual items) and from 1 = no sensation to 5 = as intense as making the movement (kinesthetic items). All items are first visually imaged (Visual subscale) and then kinesthetically (Kinesthetic subscale). Performance on the questionnaire can be reported with total scores ranging from 10 to 50 (KVIQ-10), 20 to 100 (KVIQ-20), or 34 to 170 (KVIQ-34), subscale scores (divide the previous ranges by 2), and mean individual item scores (range, 1-5), where higher values mean better ability.

Spanish MIQ-RS Version

It is a self-administered tool that assesses imagery ease/difficulty.16 It has one version of 14 items, with two 7-item subscales (Visual and Kinesthetic) whose items are interspersed during the administration. Each item follows the same procedure as in the KVIQ. The participant rates the ease or difficulty of generating the image on a 7-point scale from 1 = very hard to see/feel to 7 = very easy to see/feel, rather than the self-assessed intensity of the visual or kinesthetic sensations. Scores can be recorded as total (14-98), subscale (7-49), or individual item (1-7) values, where higher scores indicate better ability.

Experimental Procedure

All participants were evaluated twice (7- to 15-day interval) with the paper based Spanish KVIQ and MIQ-RS by the same experienced examiner at the Association facility. All participants were novel to MI techniques and were not explicitly instructed to perform or not to perform mental practice between assessments. Participants were not asked to change their regular medication schedule and were evaluated in the “on” medication state (ie, 1-2 hours after the antiparkinsonian medication intake).39 Interviews confirmed that medication status did not change during the period of study participation. To avoid medication dosing effects, all participants were tested at the same time of day for each of the 2 sessions and environmental conditions remained constant during both assessments. Administration of both questionnaires followed the recommendations and procedures described by their original authors. On the first assessment day, the KVIQ extended version was administered first and then the MIQ-RS. On the second assessment day, the order was counterbalanced. We excluded participants from the analyses if any data were lost after the assessments or from test to retest.

Psychometric Assessment and Statistical Analysis

The Statistical Package for the Social Sciences (SPSS Statistics for Windows, version 25.0; IBM Corp, Armonk, New York) was used. All analyses were conducted with 95% confidence intervals and α = 0.05 for statistical significance. The Shapiro-Wilk test for data normality indicated that nonparametric statistics should be used.

Assessing structural validity is an essential step as a part of the psychometric analysis according to COSMIN standards.28 Although it is recommended that sample size should be at least 5 times the number of items (or n > 100) to perform factor analysis, given the lack of this analysis in previous studies evaluating the validity of MI questionnaires in people with PD,17 we assessed the internal structure of each questionnaire and version (KVIQ) with an exploratory factor analysis. The Kaiser-Meyer-Olkin and Bartlett's sphericity tests were performed to determine whether factor analysis should be used, with a cut point of more than 0.5 and P < 0.01, respectively. The principal axis factoring extraction method with Promax rotation was used. If the bidimensional structure of the questionnaire/version was confirmed, the next analyses were conducted for both total and subscale scores independently.

Reliability was first tested as internal consistency. We used Revelle's ω total coefficient, which is optimal when data are non-normally distributed and the questionnaire is not unidimensional or tau-equivalent.40,41 We used the RStudio software (RStudio Team, 2020; RStudio: Integrated Development for R; RStudio, PBC, Boston, Massachusetts; http://www.rstudio.com) via calling the “omega” function from the “psych” R package to obtain ω coefficient.41 Test-retest reliability was tested with the ICC using a 2-way mixed-effects model with absolute agreement of single measures (3,1).33 According to COSMIN standards, there is currently no consensus on whether ICCs should be replaced by nonparametric alternatives when non-normal distributions are present42 and thus we used this measure as the best consensus-based approach.28 Acceptable values were ω > 0.7 and ICC > 0.5.

Limits of agreement were assessed with differences between the first-day and second-day tests plotted against the means of the 2 measurements by Bland-Altman plots.43 Measurement error was also tested using standard error of measurement (SEM) and smallest detectable change (SDC) with a 95% confidence interval,44 as SEM = SD * √1 − ICC and SDC = SEM * 1.96 * √2.

Criterion validity between questionnaires was assessed by correlating KVIQ total and subscale scores (if pertinent) to their MIQ-RS counterparts. Criterion validity of the short version of the KVIQ was tested with the long version as the gold standard.45 The aforementioned analyses were tested with Spearman's rank correlation coefficient with standard interpretation46 using the Statgraphics 19 software (Statgraphics Technologies, Inc, The Plains, Virginia).

RESULTS

Thirty-five participants initially enrolled in the study completed both assessment sessions, with a mean interval of 10.43 days (SD = 2.56) between test and retest, without any missing data or items. Participants did not report having practiced MI within the study period.

Motor Imagery Ability

Mean total, visual, and kinesthetic scores of the different KVIQ versions (long, short, and extended), as well as MIQ-RS, are listed in Table 2. According to the Wilcoxon signed-rank test, there were no significant differences between visual and kinesthetic scores in any of the KVIQ versions (P = 0.929, P = 0.97, and P = 0.606 for the KVIQ-20, KVIQ-10, and KVIQ-34, respectively) or the MIQ-RS (P = 0.097), suggesting equivalent visual and kinesthetic vividness.

Table 2 - Total, Visual, and Kinesthetic Scores of the Spanish KVIQ (Long, Short, and Extended Versions) and MIQ-RSa
All Participants (N = 35) TD Phenotype (n = 9) PIGD Phenotype (n = 25)
Questionnaire Mean SD Mean SD Mean SD
KVIQ-20 Total 72.86 20.52 75.79 20.92 71.04 20.71
KVIQ-20 Visual subscale 36.23 12.27 37.01 15.72 35.56 11.24
KVIQ-20 Kinesthetic subscale 36.63 10.43 38.78 10.2 35.48 10.62
KVIQ-10 Total 37.06 10.15 38.67 9.41 36.2 10.62
KVIQ-10 Visual subscale 18.43 6.05 18.78 7.69 18.16 5.61
KVIQ-10 Kinesthetic subscale 18.63 5.31 19.89 4.46 18.04 5.65
KVIQ-34 Total 125.4 34.53 129.34 34.46 122.8 35.27
KVIQ-34 Visual subscale 62.6 20.89 63.33 26.93 61.2 19.13
KVIQ-34 Kinesthetic subscale 62.8 17.44 66.01 16.82 61.08 17.92
MIQ-RS Total 72.91 19.59 74.01 12.85 72.13 21.98
MIQ-RS Visual subscale 37.00 11.33 36.11 13.01 37.12 11.14
MIQ-RS Kinesthetic subscale 35.91 10.35 37.9 6.95 35.01 11.49
Abbreviations: KVIQ-(10/20/34), Kinesthetic and Visual Imagery Questionnaire (short/long/extended); MIQ-RS, Movement Imagery Questionnaire-Revised Second Edition; PIGD, postural instability/gait difficulty; TD, tremor dominant.
aOne of the participants was categorized as “indeterminate” according to motor phenotype classification and their data are not shown in this table.

Structural Validity

Kaiser-Meyer-Olkin criteria for adequate measure of sampling adequacy of more than 0.855, with an acceptable minimum of 0.5, and Bartlett's sphericity tests (χ2 ≥ 479.414, df ≥ 91, P < 0.001) indicated it was pertinent to use factor analysis for the MIQ-RS, KVIQ-20, and KVIQ-10. However, it was not possible for the KVIQ-34 due to excessively high collinearity between items and thus its psychometric assessment was performed only as a total score and not as 2-dimensional tool. Two factors explained the 70.63%, 67.43%, and 65.08% of total variance for the MIQ-RS, KVIQ-20, and KVIQ-10, respectively, therefore showing evidence of their 2-dimensional underlying structure. These factors were related to each other with r = 0.6-0.63, which indicated that a nonorthogonal rotation was needed. Visual items were grouped together with Factor 1, which explained 53.5% to 58.73% of variance, and kinesthetic items did the same with Factor 2, which explained 11.59% to 11.9% of variance. Mean individual item scores and their factor loadings (each KVIQ version independently) are shown in Table 3.

Table 3 - Mean Score of the Individual Items for the KVIQ-20, KVIQ-10, and MIQ-RS and Their Factor Loadingsa
KVIQ-20 KVIQ-10 MIQ-RS
Factor Factor Factor
Item Mean SD 1 2 Item Mean SD 1 2 Item Mean SD 1 2
Item 10Vd 3.8 1.45 0.941 ... Item 8Vd 3.74 1.42 0.91 ... Item 13 (V) 4.91 1.77 0.960 ...
Item 7Vnd 3.83 1.29 0.936 ... Item 9Vnd 3.54 1.44 0.864 ... Item 10 (V) 5.23 1.76 0.902 ...
Item 8Vd 3.74 1.42 0.876 ... Item 5Vd 3.91 1.31 0.741 ... Item 4 (V) 5.11 1.74 0.897 ...
Item 9Vnd 3.54 1.44 0.865 ... Item 6V 3.66 1.43 0.729 ... Item 8 (V) 5.00 1.79 0.886 ...
Item 2V 3.4 1.44 0.847 ... Item 3Vnd 3.57 1.5 0.722 ... Item 2 (V) 5.23 2.00 0.818 ...
Item 3Vnd 3.57 1.5 0.819 ... Item 5Kd 3.69 1.28 ... 0.974 Item 5 (V) 5.14 1.88 0.774 ...
Item 1V 3.26 1.48 0.809 ... Item 8Kd 3.97 1.2 ... 0.829 Item 14 (V) 4.89 1.90 0.753 ...
Item 5Vd 3.91 1.31 0.754 ... Item 9Knd 3.71 1.2 ... 0.793 Item 9 (K) 5.34 1.76 ... 0.897
Item 4Vd 3.51 1.54 0.734 ... Item 6K 3.63 1.29 ... 0.714 Item 6 (K) 5.46 1.68 ... 0.864
Item 6V 3.66 1.43 0.694 ... Item 3Knd 3.63 1.46 ... 0.505 Item 7 (K) 5.43 1.78 ... 0.858
Item 10Kd 3.86 1.22 ... 0.985 Mean 3.71 1.35 ... - Item 11 (K) 5.11 1.85 ... 0.828
Item 5Kd 3.69 1.28 ... 0.922 Item 12 (K) 5.29 1.65 ... 0.811
Item 8Kd 3.97 1.2 ... 0.88 Item 3 (K) 5.37 1.80 ... 0.587
Item 9Knd 3.71 1.2 ... 0.808 Item 1 (K) 5.40 1.80 ... 0.569
Item 7Knd 3.86 1.22 ... 0.772 Mean 5.20 1.80 ... -
Item 6K 3.63 1.29 ... 0.76
Item 4Kd 3.51 1.31 ... 0.75
Item 1K 3.37 1.33 ... 0.664
Item 2K 3.4 1.46 ... 0.555
Item 3Knd 3.63 1.46 ... 0.537
Mean 3.64 1.36 ... -
Abbreviations: d, dominant side; K, kinesthetic; KVIQ-(10/20), Kinesthetic and Visual Imagery Questionnaire (short/long); MIQ-RS, Movement Imagery Questionnaire-Revised Second Edition; nd, nondominant side; V, visual.
aFactor loadings less than 0.2 have been removed.

Reliability

Internal consistency, test-retest reliability, SEM, and SDC results are reported in Table 4. Wilcoxon signed-rank tests for all questionnaires and their subscales (when pertinent) confirmed there were not statistically significant differences between test and retest scores (P > 0.05), suggesting that a learning effect was absent. Revelle's ω total values of 0.9 or more for the overall scores and subscales (when pertinent) provided evidence of excellent internal consistency. ICC = 0.59-0.75 showed moderate test-retest reliability. The Visual subscales of all questionnaires exhibited higher ICCs than their Kinesthetic counterparts. Bland-Altman plots for the KVIQ-20 and MIQ-RS are shown in Figure 1.

Table 4 - Reliability Results of the Total, Visual, and Kinesthetic Scores for the KVIQ (Short, Long, and Extended Versions) and MIQ-RS
Day 1 Day 2
Revelle's ω Total Coefficient Mean SD Mean SD ICC (95% CI) SEM SDC
KVIQ-20 Total 0.97 72.86 20.52 78.94 16.33 0.663 (0.410-0.818) 11.92 33.02
KVIQ-20 Visual subscale 0.96 36.23 12.27 40.02 9.33 0.656 (0.395-0.815) 7.19 19.94
KVIQ-20 Kinesthetic subscale 0.94 36.63 10.43 38.91 8.73 0.585 (0.323-0.765) 6.72 18.63
KVIQ-10 Total 0.94 37.06 10.15 39.94 8.17 0.673 (0.428-0.823) 5.56 15.41
KVIQ-10 Visual subscale 0.91 18.43 6.05 20.17 4.64 0.674 (0.425-0.824) 3.3 9.14
KVIQ-10 Kinesthetic subscale 0.9 18.63 5.31 19.77 4.49 0.604 (0.349-0.777) 3.3 9.14
KVIQ-34 Total 0.97 125.4 34.53 134.06 27.31 0.692 (0.463-0.833) 19.16 53.12
MIQ-RS Total 0.97 72.91 19.59 71.77 17.63 0.681 (0.452-0.825) 11.15 30.9
MIQ-RS Visual subscale 0.96 37.00 11.33 36.40 10.34 0.752 (0.562-0.867) 5.71 15.83
MIQ-RS Kinesthetic subscale 0.92 35.91 10.34 35.37 9.37 0.671 (0.437-0.819) 5.99 16.59
Abbreviations: ICC, intraclass correlation coefficient; KVIQ-(10/20/34), Kinesthetic and Visual Imagery Questionnaire (short/long/extended); MIQ-RS, Movement Imagery Questionnaire-Revised Second Edition; SDC, smallest detectable change; SEM, standard error of measurement.

F1
Figure 1:
Bland-Altman plots for the total, visual, and kinesthetic scores of the Spanish KVIQ-20 and MIQ-RS. (A-C) Plots for the MIQ-RS and (D-F) plots for the KVIQ-20. Each panel show the difference between test and retest plotted against the mean of the 2 days. The mean difference (continuous line) and upper and lower limits for a 95% confidence interval (discontinuous lines) are shown in blue, red, and green for the total, visual, and kinesthetic scores of both questionnaires, respectively. KVIQ-20, Kinesthetic and Visual Imagery Questionnaire (long); MIQ-RS, Movement Imagery Questionnaire-Revised Second Edition. This figure is available in color online (www.jnpt.org).

Criterion Validity

The overall and subscale scores of the KVIQ-20 were statistically significant (P < 0.01), positively and strongly (r > 0.7) correlated to their MIQ-RS counterparts (Figure 2). The same was found for the KVIQ-10 and MIQ-RS correlations, thus showing evidence of strong criterion validity between these measures. The KVIQ-10 was strongly and significantly correlated to the KVIQ-20 for the overall, visual, and kinesthetic scores (r = 0.97, r = 0.98, and r = 0.96, respectively; P < 0.01). The overall score of the KVIQ-34 was correlated to the MIQ-RS, KVIQ-20, and KVIQ-20 overall scores (r = 0.82, r = 0.99, and r = 0.98, respectively; P < 0.01).

F2
Figure 2:
Spearman's rank correlation coefficients between the total and subscale scores (if pertinent) of the Spanish KVIQ and MIQ-RS. KVIQ-(10/20/34), Kinesthetic and Visual Imagery Questionnaire (short/long/extended); MIQ-RS, Movement Imagery Questionnaire-Revised Second Edition. This figure is available in color online (www.jnpt.org).

DISCUSSION

In this study, we provide evidence for the validity (structural and criterion) and reliability (internal consistency, test-retest, measurement error) of the Spanish MIQ-RS and KVIQ in people with PD. To the best of our knowledge, this is the first study that assesses the suitability of the MIQ-RS in this movement disorder. Our results showed evidence of a good psychometric behavior of the MIQ-RS and the long and short versions of the KVIQ, in comparison with its extended version whose factor structure could not be confirmed.

Our observations are in accordance with previous studies showing evidence of the 2-dimensional structure of these instruments in people with stroke and multiple sclerosis.15,22 Here, we further found that the short and long versions of the Spanish KVIQ as well as the MIQ-RS showed equivalent structural validity and excellent internal consistency in people with PD. However, in our study, it was only possible to extract the 2 theoretical factors in the long and short versions of the KVIQ, since very high collinearity between items was found in the extended version. This reflected that some dominant or nondominant upper- and lower-limb items were nearly totally predicted by the others, contained in the KVIQ-20, and therefore in this version the score should not be interpreted as 2 separate subscales but as an overall score.47 The problem of high collinearity is a well-known limitation of long psychometric questionnaires measuring closely related constructs,48 where some redundancy is expected between items.49 This was illustrated by Revelle's ω total ≥ 0.95 for the total and visual KVIQ-20/MIQ-RS and total KVIQ-34 scores in our study. In this context, perhaps the use of the KVIQ-10 is recommendable as there is evidence of its appropriate factor structure and excellent internal consistency, as well as good test-retest reliability and similar measurement error.

Test-retest reliability assessment yielded lower ICCs than previous studies that analyzed the English KVIQ-34 or the German KVIQ-20/KVIQ-10 in people with PD.17,18 The English version accomplished almost excellent reliability for the total, visual, and kinesthetic scores (ICC > 0.8), whereas the German version showed lower data for the KVIQ-20 (ICC = 0.86, 0.68, and 0.82, respectively) or the KVIQ-10 subscales (Visual: ICC = 0.69; Kinesthetic: ICC= 0.84). However, our results showed that ICCs ranged from 0.58 to 0.69, which substantially differ from these previous studies. While the non-normal distribution of our data might have influenced the values of the ICC,42 other factors might explain these inconsistencies as well. For instance, previous work used a one-way random-effects model of the ICC but a 2-way mixed-effects model should be used when assessing test-retest reliability.33 In addition, the type and definition of the ICC were not specified, which is relevant in the process of selecting and reporting. Moreover, sample sizes were significantly smaller (n = 11 and n = 8 vs n = 35), and participants had different clinical characteristics (eg, Hoehn and Yahr stages 1-2.517 or mean disease duration of 5.2 years, SD = 3.4,18 vs stages 1-4 or disease duration of 8.8 years, SD = 5.9, in our study). These elements should be considered when interpreting ICCs of the different translations and versions of the KVIQ in people with PD, which may have been overestimated in previous literature. Conversely, the MIQ-RS showed test-retest reliability similar to previous studies,23 with ICCs ranging from 0.67 to 0.75, which is likely to reflect the consistency of MI questionnaires over time more appropriately.

Consistent positive strong correlations between questionnaires suggested high criterion validity, which is in accordance with precedent works.17,23 Nonetheless, both instruments should not be used interchangeably in clinical practice, as there are substantial differences between them. On the one hand, the KVIQ evaluates simpler and joint-specific movements of the neck, trunk, and upper/lower limbs (eg, neck flexion, hand finger tapping, hip abduction, or foot stepping), though their functional significance is reduced. However, the MIQ-RS assesses functionally meaningful movements but with an almost exclusive focus on upper-limb tasks (eg, grasping a glass and lifting it off a table or opening a door). On the other hand, in our experience, the administration of the KVIQ long and extended versions takes up to 30 minutes but the MIQ-RS and the KVIQ short version need approximately/about 10 minutes, which is of importance when evaluating their applicability to clinical practice. These differences should be considered when administering them to people with PD, as well as the psychometric properties obtained in this study.

The results obtained in this work should be interpreted considering the clinical characteristics of the participants enrolled. For instance, PIGD motor phenotype of PD was present in most participants (n = 25), and this fact might have impacted on the psychometric analyses considering there is evidence suggesting that tremor may modify MI by modulating central somatosensory processing.50 Nevertheless, the effect of PD motor phenotype (PIGD or TD) on imagery ability remains largely unexplored. In addition, despite participants were in a broad range of Hoehn and Yahr stages (1-4), mild to moderate stages (1.5-3) were predominant (n = 31). Specifically, most participants were in stages 2.5 or 3 (n = 21), which is of importance considering that MI ability seems to correlate with disease severity (measured with the MDS-UPDRS) in “on” medication states.51 However, there is parallel evidence showing nonsignificant correlations between measures of imagery ability and the Hoehn and Yahr scale.24,52 Future lines of work with larger sample sizes may be opened in light of these inconsistencies.

Study Limitations

Because of the specific clinical characteristics of the participants regarding their motor phenotype or the Hoehn and Yahr stage, the generalizability of our results is limited. Some methodological limitations should also be considered. First, we intentionally used a counterbalanced order on the second assessment day to avoid learning effects, but this fact could have affected test-retest reliability producing an order effect. In addition, we used ICCs to assess test-retest reliability despite our data showed non-normal distributions across all variables studied. Because ICC assumes data to be normally distributed, this may have affected the results.53 Nonetheless, there is currently no international consensus on alternatives to the ICC in such cases.42

Second, questionnaires were administered in the “on” medication state, which limits the applicability of our results despite motor fluctuations appear to not significantly modify MI ability.51 Finally, although our sample size was sufficient to evaluate test-retest reliability,32 it should be considered small by the requirements of the COSMIN guidelines for assessing structural validity using factor analysis.28 However, exploratory factor analysis can be used in studies with n < 50 under some conditions that apply to this work, such as high factor loadings, a low number of factors, or a high number of variables.54

Clinical Implications

Our results have several contributions to clinical practice. MI ability assessment in Spanish-speaking people with PD can now be conducted accurately using 2 easily administered, simply interpretable, and inexpensive measures. This is a major advantage for clinicians as other assessment methods of imagery ability (ie, neuroimage techniques or electrophysiological measures) require complex procedures, expensive equipment, and extensive experience by the examiner, which limits their clinical usability, applicability, and interpretability. Furthermore, SEM and SDC of the questionnaires are provided. Therefore, clinical practitioners aiming to use mental representation techniques (MI or action observation) can evaluate MI ability with these tools and determine precisely how this capacity changes with training programs.

MI modality-specific vividness can be independently assessed with these measures that are able to distinguish between visual and kinesthetic imagery. Importantly, it is not mandatory to complete the whole questionnaires, as subscales can be administered in isolation, which may be of interest in specific clinical contexts. Finally, there is evidence of the validity and reliability of the KVIQ short version (KVIQ-10), which can now be administered to people with PD and it is significantly less time-consuming than its long counterpart.

CONCLUSIONS

The results provide evidence of the validity and reliability of the Spanish MIQ-RS and KVIQ long and short versions to assess MI vividness in people with PD. The KVIQ extended version (KVIQ-34) should be used cautiously because there is no evidence of an adequate structural validity in this population.

ACKNOWLEDGMENTS

The authors thank all the participants for their time and willingness. The authors also thank Dr Carmen Bravo-Llatas and Rubén Fernández-Matías, PT, for their statistical advice.

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Keywords:

assessment; Parkinson disease; motor imagery; test-retest reliability; vividness

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