The reliability and validity of the Korean version of the reaching performance scale for stroke after translation and cross-cultural adaptation : Medicine

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Research Article: Observational Study

The reliability and validity of the Korean version of the reaching performance scale for stroke after translation and cross-cultural adaptation

Park, Ji Eun OTa; Park, So Hyun MDa; Lee, Jun Hee MDa; Ryu, Byung-Ju MD, PhDb; Hwang, Soon-Young PhDc; Baek, Seung Jun PhDd; Yang, Seung Nam MD, PhDa,*

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Medicine 102(11):p e33261, March 17, 2023. | DOI: 10.1097/MD.0000000000033261
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1. Introduction

Upper limb impairment occurs in more than 80% of patients who suffer a stroke, and only 5% to 20% of these patients will completely recover.[1–3] Following a stroke, significant changes in the ability of central nervous system to regulate muscle activation makes patients exhibit some compensation behavior, such as excessive movement of the trunk or scapula, when performing certain tasks.[4–6] These compensatory movements lead to improvements in functional performance in the short term, but repeated and stereotypical movements may also interfere with the patient’s long term recovery.[7,8] Therefore, a quantitative evaluation of compensatory movements is essential for establishing strategies for rehabilitation treatment.

There were various measurement tools for upper extremity function of stroke, But all of these evaluation tool is focused on whether to perform or not. In order to quantify the movement quality, complex and difficult evaluations such as kinematic analysis should be used.[9]

The reaching performance scale for stroke (RPSS) was developed by Levin et al[10] to assess the compensatory movements required for upper extremity reaching in people with hemiplegia secondary to stroke. It is an observational kinematic tool that can quantify the movement quality and compensation for the upper extremity and trunk as well as the overall task performance during reaching and while grasping an object. The RPSS evaluates 6 components of movement (trunk displacement, movement smoothness, shoulder movement, elbow movement, prehension, and global performance) while reaching and grasping both near and far targets. Since reaching and grasping movements are included in almost all aspects of daily life, these movements offer the advantage of not only being clinically essential but also being simple to evaluate.

Although the RPSS is a simple and useful tool, the language and cultural differences between English and Korean present barriers to its widespread use in Korea because it is developed in English. The objective of this study was to develop a Korean version of reaching performance scale for stroke (K-RPSS) through translation and cross-cultural adaptation and to investigate the reliability and validity of the K-RPSS in individuals with hemiplegia after stroke before its application in Korea.

2. Materials and Methods

Permission to translate the original form of the RPSS to the Korean language was obtained from the developer of the RPSS (Dr MF Levin). The translation and cross-cultural adaptation of the RPSS into Korean followed the guidelines set by Beaton et al[11]

2.1. Translation and cross-cultural adaptation

First, the original RPSS was independently translated from English to Korean by 2 experts (a physiatrist and an occupational therapist) with an average clinical experience of more than 15 years who were fluent in both English and Korean. After the forward translation, the 2 independently translated Korean versions were combined to form a consensus version by reconciling inconsistencies through discussion until a consensus was reached. Two translators and 1 recording observer participated in this process. The consensus version was then reverse translated back into English by 2 bilingual people (2 professors of health science) with more than 12 years of clinical experience or research who were native English speakers and also fluent in Korean. This process was carried out in a state in which the original 1 was completely blind. The 2 back-translation versions were combined into a single English 1 after discussion. The backward translation version in English was reviewed by the original 2 translators, and they confirmed that the Korean version reflected the same content as the original RPSS and that there were negligible differences that remained after comparing the original English version of the RPSS and the backward-translated version of the RPSS. After that, the experts and investigator (2 physiatrists, 2 occupational therapists and 2 physical therapists) with an average 5 years of clinical experience and familiarity with stroke reviewed and reconfirmed all translated versions to consider conceptual equivalents rather than a literal translation and developed the pre-final version for field testing. The pre-final version was tested by 1 medical doctor and 1 occupational therapist with more than 10 years of clinical experience to identify any interpretation problems and to review and correct the questions and responses. After this process, the Korean version of the RPSS was finally developed.

2.2. Participants

In accordance with the Korea University Medical Center Institutional Review Board (IRB No. 2021GR0178), written informed consent was obtained from each patient prior to the study. Ninety-eight Korean speaking patients with post stroke hemiplegia were consecutively enrolled from Guro Hospital, Korea University Medical Center, and Sahmyook Medical Center. The inclusion criteria for this study were as follows: People with hemiplegia due to stroke; Who were older than 18 years of age, and; Cognitively able to understand instructions and perform tasks appropriately. Participants with a history of a brain tumor, severe aphasia, and decreased levels of cognition were excluded. The demographic and clinical characteristics of the participants are shown in Table 1.

Table 1 - General characteristics and clinical data of participants.
Sex 67 male, 31 female
Age 63.63 + 13.13 yr
BMI 23.20 + 3.19
Type of stroke
 Ischemic 71
 Hemorrhagic 27
Side of hemiplegia right 51, left 47
Time after post stroke (wk) 97.82 + 191.50
K-NIHSS 5.47 + 3.05
FMA for upper extremity 47.45 + 19.81
MFT affected 19.21 + 9.11, less affected side 27.64 + 4.05
Data are presented as numbers of patients or as mean + standard deviation.
BMI = body mass index, FMA = Fugl-Meyer assessment, K-NIHSS = Korean version of the national institute of health stroke scale, MFT = manual function test.

2.3. The Korean version of the reaching performance scale for stroke

The participants were seated in chairs with a backrest but no armrests in front of a table. The RPSS tasks included reaching and grasping a plastic cone that had been placed on the table as both near and far targets (1 cm and 20 cm from the edge of the table). With the participant’s consent, their performance of the task was videotaped for subsequent analysis. A camera was positioned diagonally with the frontal plane at around 30 degrees on the non-paretic side of the patients. The K-RPSS consists of reach-to-grasp tasks for both close and far targets, and each task includes 6 components. Five of these components are to evaluate the performance of close and far targets for trunk displacement, movement smoothness, shoulder movement, elbow movement, and prehension. The last component, the global score, evaluates the global quality of the performance, which may be related to the first 5 components. Each component is evaluated using a 4-point ordinal scale ranging from 0 to 3 points. Close targets and far targets can be evaluated using a range from 0 to 18 points, and the total K-RPSS score ranges from 0 to 36. The Fugl-Meyer Assessment (FMA) for the upper limb and the manual function test (MFT) were also administered to examine any motor impairment and the functional status of the patient’s upper limb.[12,13]

2.4. Reliability

The test-retest reliability of the K-RPSS was estimated by measuring whether the test was consistent over time (intra-rater reliability) and across people (inter-rater reliability). As required by the test-retest method for the analysis of reliability, 1 medical doctor and an occupational therapist with more than 5 years clinical experience who were not involved in the development of K-RPSS viewed the videotapes separately and rated the K-RPSS score. The intraclass correlation coefficient (ICC) was calculated to estimate the inter-rater reliability between 2 evaluators. After that they repeated the evaluation after 1 week using same videotapes for determination of intra-rater reliability. The ICC was calculated to estimate the intra-rater reliability between the initial and second K-RPSS scores. ICC values between 0.75 to 0.9 indicate good reliability, and values < 0.90 suggest excellent reliability.[14]

The internal consistency reliability across each item of the K-RPSS was measured using the Cronbach alpha, an index of whether the items included in 1 measurement tool were closely related to each other. Generally, a Cronbach alpha of ≥ 0.80 indicates good internal consistency, while a Cronbach alpha ≥ 0.90 indicates excellent internal consistency.[15]

2.5. Validity

To assess the concurrent validity, an analysis was carried out using the Spearman rank correlation coefficient of the between partial score (close and far targets, respectively) or the total K-RPSS score and other evaluation tools for patients with upper limb function difficulties following a stroke, such as the FMA and MFT. Values >0.6 indicated a strong correlation.[16]

Confirmatory factor analysis was carried out to investigate the factor structure of K-RPSS. The model was tested using covariance matrix and maximum likelihood estimation method. To assess model fit, we used the chi-square statistics (χ2) relative/normed chi-square (χ2/df), the compariative fit index (CFI), the root mean square error of approximation (RMSEA) and the standardized root mean square residual (SPMR). A χ2/df ratio of <3 is considered indicative of a good fit between the hypothetical model and the sample data. For other goodness of fit indexes, values indicative of good fit are CFI, >0.90, RMSEA < 0.06 and SRMR < 0.08.[17,18]

2.6. Measurement error

The standard error of measurement (SEM) was calculated to estimate the measurement error of the test, and the smallest real difference was calculated by 1.96 ×√2 × SEM (1.96 was the 95% confidence interval, √2 was the difference in the 2 variances).[19] The SRD indicates whether a person’s change in score is a true change at the 95% confidence interval level.

2.7. Statistics

All statistical analyses were performed using International Business Machines Statistical Package for the Social Sciences, version 25.0 (IBM Corp., Armonk, NY) and MedCalc, version 20.027 (MedCalc Software Ltd., Ostend, Belgium) and SAS (SAS 9.4, SAS Institute, Cary, NC).

3. Results

Ninety-eight participants (67 males, 31 females) and their general and clinical information are detailed in Table 1. The mean K-RPSS score of the participants was 25.52 + 10.91 (range: 0–36). The K-RPSS scores of each of the 6 components for close and far targets are shown in Table 2. The internal consistency of the 6 items of the K-RPSS was demonstrated be excellent (Cronbach alpha = 0.956 for close targets, 0.955 for far targets, and 0.977 for the total score). Of all participants, 17.5% received 36 points (a perfect score), and 5.2% received 0 points. Since more than 15% of the respondents achieved the highest possible score, the K-RPSS can be interpreted to have a ceiling effect.[15,20]

Table 2 - Six components of Korean version of reaching performance scale for stroke.
Component Close target Far target
Trunk displacement 2.47 + 0.91 2.34 + 1.02
Movement smoothness 1.78 + 1.00 1.72 + 1.03
Shoulder movement 2.37 + 0.92 2.36 + 0.95
Elbow movement 2.34 + 1.02 2.33 + 1.01
Prehension 1.98 + 1.14 1.87 + 1.20
Global score 2.02 + 0.98 1.93 + 0.97
Total score 12.97 + 5.43 12.55 + 5.60
Data are presented as mean + standard deviation.

3.1. Test-retest reliability of the K-RPSS

The intra-rater reliability of the K-RPSS total score as well as the partial score (for close and far targets) that were evaluated using the ICC were excellent in this study. The inter-rater reliability of the K-RPSS total score and the partial score between Raters 1 and 2 were also excellent (Table 3).

Table 3 - The reliability of Korean version of reaching performance scale for stroke.
Intra-rater Inter-rater
Score ICC (95% CI) ICC (95% CI)
Close target 0.9842 (0.9766–0.9894) 0.982 (0.9734–0.9879)
Far target 0.9808 (0.9715–0.9871) 0.9806 (0.9711–0.9870)
Total 0.9865 (0.9799–0.9910) 0.9866 (0.9800–0.9910)
CI = confidence interval, ICC = intraclass correlation coefficient.

3.2. The correlation of the K-RPSS with the FMA for the upper limb and MFT

The validity of the K-RPSS was confirmed to have a strong correlation with the FMA for the upper limb (R = 0.664, P = .000) and the MFT (R = 0.671, P = .000) (Fig. 1). The K-RPSS subscore for close targets and far targets also had a strong correlation with the FMA for the upper Limb and the MFT scores, respectively (Table 4).

Table 4 - Correlation of Korean version of reaching performance scale for stroke with Fugl-Meyer assessment for upper extremity and manual function test.
Parameter Total score Close target Far target
FMA for upper limb 0.634* 0.751* 0.738*
MFT 0.671* 0.700* 0.745*
Data are presented as Spearman rho.
FMA = Fugl-Meyer assessment, MFT = manual function test.
*P < .001.

Figure 1.:
Relationship between (A) the FMA for upper limb and K-RPSS and (B) the MFT and K-RPSS. r = correlation coefficient. K-RPSS = Korean version of reaching performance scale for stroke, MFT = manual function test.

3.3. Factor analysis

The confirmatory factor analysis was used to evaluate the goodness of fit of the 2-factor (close target, far target) structure of K-RPSS in 98 patients. The value of the fit was not good (χ2 = 510.9013, χ2/df = 53, P < .001, CFI = 0.7595, RMSEA = 0.3, SPMR = 0.0566). The goodness of fit of 6 factor (Trunk displacement, Movement smoothness, Shoulder movement, Elbow movement, Prehension, Global score) structure of K-RPSS was also evaluated using confirmatory factor analysis. The goodness of the fit was improved but some of the indices were acceptable but some of them were not still good (χ2 = 168.0688, χ2/df = 39, P < .001, CFI = 0.9322, RMSEA = 0.1857, SPMR = 0.0188).

3.4. Measurement error

The SEM was 1.108, and the SRD was 3.071. These results indicate that a change of approximately 3 points is the score change needed to indicate a statistical significance change of K-RPSS.

4. Discussion

This study conducted a formal translation and cross-cultural adaptation of the original RPSS into the Korean language. The K-RPSS demonstrated excellent intra-rater and inter-rater reliability and internal consistency. In addition, the concurrent validity was evaluated as good and had a strong correlation with the FMA for Upper Limb and MFT scores in stroke patients.

As the preliminary analysis of reliability of the original RPSS, the ICC for inter-rater reliability averaged 0.84 (range: 0.58–0.95) for the close target and 0.89 (range: 0.69–0.96) for the far target.[10] The ICC for inter-rater reliability in our results was 0.98 (range: 0.97–0.98) for both close and far targets. These 2 results differences between the original inventory and the K-RPSS may have occurred because the original RPSS had only preliminary results with a small number of patients.

The Chedoke-McMaster Stroke Assessment Scale for the arm and hand and the Grip Force and Upper Extremity Performance Test for the Elderly were used to evaluate the validity of the original RPSS, and a strong correlation between the RPSS and all the above tools was reported.[10] Recently, Subramanian et al[21] reported the concurrent validity for individual RPSS items with corresponding kinematic outcomes. Individual RPSS items for both close and far targets were mildly to moderately correlated with corresponding kinematic values. We evaluated the correlation between the K-RPSS and the FMA for the Upper Limb and the MFT test. The FMA and MFT are widely used in Korea; the FMA is a tool used to assess motor impairment, and the MFT is a functional scale. We attempted to evaluate the correlation between the K-RPSS score and both upper limb impairment and function. The K-RPSS was determined to have good validity due to its strong correlation with both the FMA and MFT. In our results, the K-RPSS was considered to have a ceiling effect. Although the K-RPSS had a good correlation with other evaluation tools like the FMA and MFT, it cannot evaluate the patients performance, especially in patients with good upper limb function. The FMA score was variously distributed from 50 to 66, and the MFT score ranged from 22 to 31 among those who had a perfect score on the K-RPSS. The K-RPSS is recommended to be used in a way that can evaluate the compensation and movement quality of patients with hemiplegia and is also a useful evaluation tool for upper limb impairment and function, much like the FMA and MFT. Prior to our study, a Brazilian-Portuguese version of the RPSS was developed, and the measurement properties of this version were reported.[22] The developers demonstrated excellent reliability and found that the internal consistency and validity with the FMA was strong; all of their findings were quite similar to ours.

To the best of our knowledge, this is the first study evaluating the factor structure of RPSS. The fitness of index was not good in 2-factor model of K-RPSS. Also, fitness of 6 factor model was variable in this research. It is thought that the model fitness was not good because the items of RPSS was highly correlated with each other. However, each item of RPSS was necessary for evaluating patient’s movement quality and compensation. The component of global score can be considered to be removed because it is relatively ambiguous to evaluate and overlaps with other components. In fact, goodness of fit was improved with 5 factors when factor of global score was removed.

The assessment of the movement quality and compensation of the trunk and upper limb is an important tool for planning the best treatment strategy and clinical management of poststroke hemiplegia. Reaching movements involve the transport of the hand in a targeted space, while grasping is shaping the hand and finger posture in anticipation of intrinsic object properties, such as size, shape, and orientation. The reaching and grasping actions represent basic movements of upper limb function in almost all activities of daily living. In addition, the amount of time required to complete a K-RPSS evaluation is short, and this test also has the advantage of being simple and easy to interpret. Experts can distinguish between high-quality and low-quality movements using compensation after close inspection of the patient’s movement behavior, but it is difficult to quantify these and to detect changes between the before and after. A 3-dimensional (3D) kinematic analysis should be required for measurements used to quantify and change the movement quality.[9] However, 3D kinematic analysis is not easily used in practice because it is time-consuming and expensive and also requires special equipment, such as a 3D motion analysis that involves placing reflective markers on the patient’s body surface, which can interfere with normal movement. The RPSS is a numerical scale that can quantify the quality of upper limb movements of each of 6 components that are easily occurring problems of compensation and low-quality movement. The same type of detailed information that can be provided by a kinematic analysis cannot be obtained from the RPSS, but it is a good enough tool for clinical use and offers the advantages of being able to be learned and evaluated quickly; it also has a high reliability and validity.

5. Conclusion

The Korean version of the RPSS has been shown to be a reliable and valid tool for assessing the compensation and movement quality of the upper limb and trunk. A 3-point score change should be used as the minimum threshold to indicate statistical significance. The K-RPSS is simple and is expected to be used widely by Korean speaking clinicians and researchers.


The authors are grateful to Dr MF Levin for permission to translate the original version of the RPSS to Korean one.

Author contributions

Conceptualization: Seung Nam Yang.

Data curation: Ji Eun Park, So Hyun Park, Jun Hee Lee, Byung-Ju Ryu.

Formal analysis: Soon-Young Hwang.

Supervision: Seung Nam Yang, Seung Jun Baek.

Writing – original draft: Ji Eun Park.

Writing – review & editing: Seung Nam Yang.


compariative fit index
Fugl-Meyer assessment
intraclass correlation coefficient
Korean version of reaching performance scale for stroke
manual function test
root mean square error of approximation
reaching performance scale for stroke
standardized root mean square residual
standard error of measurement


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hemiplegia; Korean version; reaching; reaching performance scale; stroke; upper limb

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