J Orthop Sci 2013

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J Orthop Sci DOI 10.1007/s00776-013-0426-x

ORIGINAL ARTICLE

Reproducibility and validity of the Japanese version of the Western Ontario Rotator Cuff Index Masashi Kawabata • Toru Miyata • Daisuke Nakai • Masahiro Sato • Hiroaki Tatsuki • Yuichi Kashiwazaki Hiroshi Saito

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Received: 28 January 2013 / Accepted: 30 May 2013 Ó The Japanese Orthopaedic Association 2013

Abstract Background The Western Ontario Rotator Cuff Index (WORC) is a self-report, disease-specific, quality-of-life assessment tool. Good reliability and validity have been demonstrated with several language versions of the WORC. In this study, the WORC was translated into Japanese, and its reproducibility and validity for use in Japanese patients with rotator cuff disorder were determined. Materials and methods The translated version of the WORC was certified by the developer of the original version. Of 78 consecutive Japanese patients with rotator cuff disorder, 75 completed the following questionnaires: the WORC; the Disabilities of the Arm, Shoulder, and Hand (DASH); and the Short Form 36 (SF-36). In total, 50 patients completed the WORC twice within 2–14 days.

Internal consistency, test–retest reliability, absolute reliability, and construct validity were assessed. Results Cronbach’s alpha coefficients ranged from 0.78–0.95, and intraclass correlation coefficients ranged from 0.72–0.84 for the total score as well as scores on all WORC domains. A fixed bias was revealed between the test and retest for the total score and scores of some domains. Limits of agreement (LOA) ranged from -19.0–27.9 % for the total score on the WORC. Furthermore, the WORC scores correlated with those of DASH (r = 0.63–0.78) and SF-36 (r = -0.24 to -0.69). Conclusions Good test-retest reliability and construct validity were demonstrated for the Japanese WORC, but relatively high absolute measurement errors were observed. LOA values must be considered when using the WORC for individual patients with rotator cuff disorder.

Introduction Electronic supplementary material The online version of this article (doi:10.1007/s00776-013-0426-x) contains supplementary material, which is available to authorized users. M. Kawabata (&)  T. Miyata  H. Tatsuki Department of Rehabilitation, Sagamihara Kyodo Hospital, 2-8-18 Hashimoto, Midori, Sagamihara 252-5188, Japan e-mail: [email protected] D. Nakai Department of Orthopaedics, Hachioji Sports Orthopaedic Clinic, Tokyo, Japan M. Sato Department of Rehabilitation, Hachioji Sports Orthopaedic Clinic, Tokyo, Japan Y. Kashiwazaki  H. Saito Department of Orthopaedics, Sagamihara Kyodo Hospital, Sagamihara, Japan

Rotator cuff disorder is a common problem in shoulder joints. The incidence of full-thickness rotator cuff tears observed by ultrasonography was 20.7 % in 1366 shoulders in the general Japanese population [1]. The major symptoms of rotator cuff disorder include pain with motion, or at night muscle weakness, and a joint range of motion deficit combined with joint contracture. These functional losses cause disability and restriction of activities of daily living (ADL) and useful work. In many cases, health-related quality of life (HRQOL) is affected as well [2, 3]. Assessing patients with rotator cuff disorder requires consideration of two areas of potential discrepancy between subjective and objective conditions. First, sometimes a gap is observed between ultrasonographic findings and physical symptoms; in one report, approximately two

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thirds of individuals with full-thickness rotator cuff tears had no symptoms [4]. Second, physical symptoms, muscle strength, and joint range of motion may correlate poorly with the ability to perform ADL and useful work [3]. Therefore, comprehensive assessment of symptoms, shoulder function, ability to perform ADL, and HRQOL is required to determine the true condition of patients with rotator cuff disorder. The English version of the Western Ontario Rotator Cuff Index (WORC) was developed by Kirkley et al. [5]. WORC is a self-report, disease-specific, HRQOL assessment tool for use in patients with rotator cuff disorder. It comprises 21 items in five domains (physical symptoms, sports/recreation, work, lifestyle, and emotions) and is scored from 0 (asymptomatic) to 2100 (worst), with each item receiving 0–100 points. Recently, the number of studies using the WORC as an outcome measurement have increased, and the reliability, validity, and responsiveness of several language versions of the WORC have been reported as well [3, 6–9]. In addition, this questionnaire can also be completed in a short time; in one report, the mean time required for completion of the WORC was about 8 min [3]. However, this disease-specific HRQOL measurement tool cannot currently be used for assessment of Japanese patients with rotator cuff disorder. In order to be used in the Japanese setting, the WORC must be translated into Japanese in accordance with the guidelines for crosscultural adaptation, after which its reliability and validity must be evaluated [10]. Adapting the WORC for use in Japanese patients would enable international comparison of outcomes for patients with rotator cuff disorder. The following were the aims and purposes of this study: to translate the WORC into Japanese and to examine its reproducibility and validity in Japanese patients with rotator cuff disorder. Our hypothesis was that the Japanese version of the WORC (the Japanese WORC) would have acceptable reproducibility and validity similar to the other language versions of the WORC.

questionnaire, discussing inconsistencies until a consensus was achieved. In accordance with the guidelines, the Japanese version was translated back into English by a professional translator. Subsequently, the back-translated version was reviewed by Dr. Griffin and carefully revised several times. In January 2010, the final Japanese version of the WORC was certified by Dr. Griffin. Patients All patients were examined by orthopedic surgeons and physical therapists at Sagamihara Kyodo Hospital. The following were the inclusion criteria for this study [7, 11]: patients had to be Japanese, aged [20 years, and suffering from a full- or partial-thickness rotator cuff tear, impingement syndrome, or tendinopathy. The diagnosis was confirmed by history, physical examination, and radiological evaluations (magnetic resonance imaging or ultrasonography) [7]. Consecutive patients included those who had either undergone physical therapy, were scheduled for surgery, or who had undergone surgery more than 3 months back [8, 9]. If patients met the inclusion criteria for both sides, the more affected side was defined as the symptomatic side. A sample size of 50 patients is appropriate for the assessment of reliability parameters [12]. Patients were excluded if they refused to provide informed consent or were aged \20 years. In addition, patients with frozen shoulder syndrome and no rotator cuff tear and those with fractures, articular rheumatism, or cervical spinal cord syndrome were excluded as well. Furthermore, patients with eyesight deficiency or dementia were excluded because of their inability to complete the self-report questionnaire. Written informed consent to participate in this study was obtained from each subject before the study. The study protocol was approved by the ethics committee of Sagamihara Kyodo Hospital (study no. 49). Assessment tools

Materials and methods Translation The translation procedures were performed in accordance with the guidelines in order to preserve equivalence in cross-cultural adaptation [10]. Permission to translate the WORC was obtained from Sharon H. Griffin, the author and owner of the original version of the WORC questionnaire. The original version of the WORC questionnaire was first translated by two physical therapists (M.K. and T.M.) independently. These two therapists and a shoulder surgeon (D.N.) compared the two versions of the

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The WORC is a self-report questionnaire comprising 21 items in five domains: physical symptoms (6 items), sports and recreation (4 items), work (4 items), lifestyle (4 items), and emotions (3 items) [5]. Patients are considered most symptomatic when they achieve the highest score of 2100, whereas they are asymptomatic when they achieve a score of 0. The score can be reported as a relative value; for example, a patient with a total score of 1625 would have a percentage score of (2100 - 1625)/2100 9 100 = 22.6 %. Using this system, the most symptomatic patients would score 0 %, whereas the most asymptomatic patients would score 100 % [5]. If a response is lacking in any domain, the lost item score can be compensated for by the mean of the

Reproducibility of Japanese WORC

other items in the domain [11]. Nevertheless, losses of more than two items in a domain cannot be compensated; they must be listed as incomplete [11]. Disabilities of the Arm, Shoulder, and Hand (DASH) is a self-report questionnaire consisting of 30 items scored on a 5-point Likert scale on the ability to perform upper limb activities [13–15]. The DASH score ranges from 0 (no disability) to 100 (most severe disability). The score cannot be computed if C4 items are missing, whereas B3 missing items can be compensated for by computing the mean score of the other items in the same domain. The Short Form 36 (SF-36) is a general health questionnaire consisting of 36 items scored on 3-, 5-, or 6-point Likert scales. It consists of eight subscales: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. The scores on each subscale range from 0 (poor health) to 100 (good health). The SF-36v2TM Health Survey is used in acute (1 week) recall versions (SF-36 version 2 Acute, in Japanese) [16, 17]; this version was used in the current study. Nevertheless, scores for lost items can be compensated for by computing the mean value of the scores using more than half of the items in a given domain.

[19]. The 95 % CI for the lower and upper LOA was estimated using the following formula [19]: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðmean  1:96  SDÞ  t  ð3SD2 =nÞ; where mean was the mean difference between the test and retest, SD was the standard deviation of the difference, t was the value of t corresponding to two-sided P = 0.05 for degree of freedom (n - 1), and n was the sample size. Construct validity of the Japanese WORC was assessed using the Pearson correlation coefficient. Because there is no gold standard for evaluating the validity of the Japanese WORC, the score was compared with other assessment tools reflecting HRQOL. Thus, correlations among the Japanese WORC, DASH, and SF-36 were evaluated using the above-mentioned assessment protocol [3, 5, 11]. In fact, the Japanese versions of DASH and SF-36 are commonly used as self-report assessment tools for HRQOL. SPSS version 11.0 software (SPSS Inc., Chicago, IL, USA) was used in the analyses.

Results Translation

Statistical analysis Internal consistency of the Japanese WORC was assessed using Cronbach’s alpha coefficient. The coefficient ranges from 0–1, with C0.7 indicating sufficient internal consistency [12]. Internal consistency assesses whether items comprising total WORC and those in each domain contribute to and correlate with the total WORC score or score for each domain, respectively [12]. Test-retest reliability was determined by calculating the intraclass correlation coefficient (ICC) [18]. The Japanese WORC was completed twice within an interval of 2–14 days by a group of stable patients [8]. Here good correlation was defined as excellent reliability with coefficients of 0.75–1.00, as good reliability with coefficients of 0.60–0.74, as fair reliability with coefficients of 0.40–0.59, and as poor reliability with coefficients of \0.40 [11, 18]. Absolute reliability was assessed using the Bland–Altman plot, which was created by plotting the differences against the mean between the test and retest [19]. Fixed bias was identified when the 95 % confidence interval (95 % CI) for the mean difference did not include zero [20]. Moreover, proportional bias was indicated when the regression slope of the difference on the mean differed significantly from zero (P \ 0.05) [20]. The limit of agreement (LOA) was calculated as the mean difference ± 1.96 9 the standard deviation of the difference

Items 7 and 17 of the back-translated version of the Japanese WORC were reviewed by the original developer of the instrument, because these items could not be translated to reflect exactly the same meaning as in the original version. After these items had been revised based on the developer’s instructions, the Japanese WORC was finalized. Patient characteristics Of 78 consecutive Japanese patients with rotator cuff disorders, 3 were excluded from the construct validity analysis because of incomplete questionnaires. Patient characteristics (n = 75) and mean values for the Japanese WORC scores are displayed in Tables 1 and 2. Missing items were as follows: 2 patients omitted 1 item on the Japanese WORC. For DASH, 22 patients omitted 1 item, 3 patients omitted 2 items, 2 patients omitted 3 items, and 2 patients omitted 4 items. For the SF-36, 3 patients omitted 1 item, 3 omitted 2 items, 1 omitted 3 items, and 1 omitted 4 items. In addition, 25 patients were excluded from the reproducibility analysis because they could not complete the Japanese WORC a second time within 2–14 days. Thus, in the final sample, 50 patients were included (28 men and 22 women; mean age, 63.2 years; mean interval between the first and second tests, 6.1 days).

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M. Kawabata et al. Table 1 Characteristics of patients with rotator cuff disorder (n = 75)

Table 2 Absolute values of all scores at the first test (n = 75) Mean (SD)

Range

95 % CI

1050.3 (449.9)

69.5–1875.0

923.6–1177.1

Physical symptoms (0–600)

265.0 (125.8)

0.0–478.0

229.6–300.5

Sports/recreation (0–400)

234.3 (92.6)

4.0–398.0

208.2–260.4

Work (0–400)

215.0 (105.4)

0.0–400.0

185.3–244.7

52 (69)

Lifestyle (0–400)

187.2 (99.4)

11.5–379.0

159.2–215.2

Left

23 (31)

Emotions (0–300)

148.8 (91.2)

0.0–300.0

123.1–174.5

Both

0 (0)

29.2 (16.1)

0.8–69.0

24.7–33.8

No. (%) Age (years)

Mean (SD)

Range

63.4 (11.1)

38.0–88.0

WORC: total (0–2100)

Sex Male Female

43 (57) 32 (43)

Affected side Right

DASH (0–100) SF-36 (0–100)

Diagnosis Impingement syndrome or tendinopathy

14 (19)

Physical functioning

81.0 (15.6)

20.0–100.0

76.6–85.4

Partial-thickness rotator cuff tear

12 (16)

71.8 (25.6) 52.9 (20.8)

0.0–100.0 10.0–90.0

64.5–79.0 47.1–58.8

10.0–97.0

Full-thickness rotator cuff tear

27 (36)

Role physical Bodily pain

Post-surgery (rotator cuff repair)

22 (29)

General health

58.6 (18.4)

Vitality

62.1 (22.6)

0.0–100.0

55.7–68.5

Social functioning

80.0 (23.3)

25.0–100.0

73.4–86.6

No. Sample size, SD standard deviation

Reproducibility and validity Table 3 presents the percentage scores on the first and second WORC, the mean difference (95 % CI) and slope of the regression between the test and retest, ICC, and LOA (95 % CI for lower and upper LOA). Furthermore, the Cronbach’s alpha coefficient for the total score and scores for each domain on the Japanese WORC are presented in Table 4. The Bland-Altman plots provided in Fig. 1 illustrate the distribution of the difference against the mean between the test and retest. Except in the sports/recreation and work domains, fixed bias existed in the results of the Japanese WORC because the 95 % CI for the mean difference (results of the second test minus the results of the first test) did not include 0 (Table 3). No proportional bias was observed in the total score and scores for all domains (Table 3; Fig. 1). Significant correlations were observed between the total scores and scores for each domain in the Japanese WORC compared with those of DASH and all subscales of SF-36 (Table 4).

53.4–63.8

Role emotional

77.8 (26.9)

0.0–100.0

70.2–85.4

Mental health

68.3 (23.1)

5.0–100.0

61.8–74.8

SD Standard deviation, CI confidence interval, WORC Western Ontario Rotator Cuff Index, DASH Disabilities of the Arm, Shoulder, and Hand score, SF-36 Short-Form 36

Japanese WORC were smaller than those of other assessment tools, the Japanese WORC would be a usable assessment tool. However, a relatively high absolute measurement error was also found. Translation Item 7 in the original version contained the phrase ‘‘fitness levels;’’ however, this phrase might be misunderstood by the Japanese, particularly older individuals. Therefore, several supplementary explanations were added to aid understanding: ‘‘How much does your shoulder affect your fitness level (e.g., your ability to go jogging, walking, and exercising in other ways)?’’ In addition, item 17 in the original version, ‘‘roughhousing and horsing around,’’ could not be translated into Japanese; thus, the sentence was revised to one with much the same meaning as per the developer’s comments: ‘‘To what extent does your shoulder impede your ability to participate in rough activity like floor wrestling with family and friends?’’

Discussion Reproducibility and validity The results of this study demonstrated acceptable reliability and validity of the Japanese WORC as a measurement tool for Japanese patients with rotator cuff disorder. In addition, because the numbers of items and missing items in the

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The internal consistency in the Japanese WORC was acceptable, as indicated by the high Cronbach’s alpha coefficients (Table 4). In fact, this internal consistency was

Reproducibility of Japanese WORC Table 3 Test–retest and absolute reliability of the Japanese WORC (n = 50) First test

Second test

d (95 % CI)

B (P value)

ICC (95 % CI)

LOA (95 % CI for lower/upper LOA)

WORC: total

48.9 (22.1)

53.4 (22.1)

4.5 (1.1–7.9)

-0.00 (0.98)

0.84 (0.72–0.91)

-19.0 to 27.9 (-24.9 to -13.1/22.0 to 33.8)

Physical symptoms

53.5 (19.8)

57.8 (22.0)

4.3 (0.6–8.1)

-0.17 (0.25)

0.78 (0.64–0.87)

-21.8 to 30.5 (-28.4 to -15.3/24.0 to 37.1)

Sports/recreation

39.6 (23.7)

43.4 (24.6)

3.8 (-0.2–7.9)

-0.07 (0.64)

0.82 (0.70–0.89)

-23.9 to 31.6 (-30.9 to -17.0/24.6 to 38.6)

Work

46.2 (27.2)

49.1 (26.3)

2.9 (-2.3–8.1)

0.06 (0.71)

0.76 (0.62–0.86)

-33.0 to 38.8 (-42.0 to -24.0/29.8 to 47.9)

Lifestyle

53.5 (25.5)

59.0 (25.7)

5.5 (0.3–10.8)

-0.02 (0.89)

0.72 (0.55–0.83)

-30.6 to 41.7 (-39.7 to -21.5/32.6 to 50.8)

Emotions

49.7 (32.4)

55.8 (30.0)

6.1 (0.4–11.7)

0.12 (0.39)

0.78 (0.64–0.87)

-33.0 to 45.2 (-42.9 to -23.2/35.4 to 55.0)

Mean (standard deviation) values are expressed in percentages (0–100 %). The second test was administered within 2–14 days from the first test WORC Western Ontario Rotator Cuff Index, d mean difference between the first and second tests, CI confidence interval, B slope of the regression, ICC intraclass correlation coefficient, LOA limits of agreement

Table 4 Internal consistency and construct validity of the Japanese WORC (n = 75) Cronbach’s a

Pearson correlation coefficients r (P value) DASH

SF-36 PF

RP

BP

GH

VT

SF

RE

MH

WORC: total

0.95

0.78* (0.00)

-0.50* (0.00)

-0.50* (0.00)

-0.69* (0.00)

-0.34* (0.00)

-0.49* (0.00)

-0.54* (0.00)

-0.51* (0.00)

-0.45* (0.00)

Physical symptoms

0.82

0.66* (0.00)

-0.40* (0.00)

-0.40* (0.00)

-0.64* (0.00)

-0.37* (0.00)

-0.54* (0.00)

-0.45* (0.00)

-0.46* (0.00)

-0.40* (0.00)

Sports/ recreation

0.78

0.70* (0.00)

-0.42* (0.00)

-0.53* (0.00)

-0.62* (0.00)

-0.24* (0.04)

-0.44* (0.00)

-0.50* (0.00)

-0.46* (0.00)

-0.39* (0.00)

Work

0.85

0.70* (0.00)

-0.50* (0.00)

-0.49* (0.00)

-0.63* (0.00)

-0.26* (0.02)

-0.36* (0.00)

-0.46* (0.00)

-0.40* (0.00)

-0.35* (0.00)

Lifestyle

0.78

0.74* (0.00)

-0.44* (0.00)

-0.38* (0.00)

-0.53* (0.00)

-0.30* (0.01)

-0.33* (0.00)

-0.49* (0.00)

-0.45* (0.00)

-0.40* (0.00)

Emotions

0.90

0.63* (0.00)

-0.46* (0.00)

-0.39* (0.00)

-0.57* (0.00)

-0.27* (0.02)

-0.46* (0.00)

-0.47* (0.00)

-0.44* (0.00)

-0.43* (0.00)

WORC Western Ontario Rotator Cuff Index, DASH Disabilities of the Arm, Shoulder, and Hand score, SF-36 Short Form 36, PF physical functioning, RP role physical, BP bodily pain, GH general health, VT vitality, SF social functioning, RE role emotional, MH mental health * P \ 0.05

similar to those of the other translated versions of the WORC (range 0.68–0.97) [3, 6–8]. Thus, this good internal consistency suggests that the items of this questionnaire correlated with the total score and scores for each WORC domain [12]. For appropriate analysis in a reproducibility study, use of the ICC and Bland-Altman plot is recommended [21]. In addition, the LOA is useful in clinical settings [11]. Good to excellent test–retest reliability was observed with the Japanese WORC within 2–14 days (ICC = 0.72–0.84). Moreover, similar reliability has been reported with the original version as well [5] (ICC = 0.96), and ICCs have ranged from 0.74–0.99 in several translated versions [6–8].

The recommended ICC for an assessment tool is ICC [ 0.7 for a large group (as in research) or ICC [ 0.9 for individuals [5, 8]. Therefore, the results of this study indicate that the Japanese WORC has sufficient reliability for use in a large group, but may be unsuitable for use in individual patient assessment. In addition, although ICC values were mostly high in this study, LOA values were relatively high as well. The emotions domain, which indicated the highest LOA of all domains, may have affected the result of relatively high LOA values in this study because the visual analog scale is susceptible to mental change [22]. As the LOA indicates the smallest within-individual variation in score, exceeding the LOA

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M. Kawabata et al.

Difference between the test and retest (%)

WORC Total

Physical symptoms

Sports/recreation

80

80

80

60

60

60

40

40

40

20

20

20

0

0

0

-20

-20

-20

-40

-40

-40

-60

-60

-60

-80

-80 0

25

50

75

-80 0

100

25

Work

50

75

100

0

Lifestyle 80

80

60

60

60

40

40

40

20

20

20

0

0

0

-20

-20

-20

-40

-40

-40

-60

-60

-60

-80

-80 25

50

75

100

50

75

100

Emotions

80

0

25

-80 0

25

50

75

100

0

25

50

75

100

Mean of the test and retest (%)

Fig. 1 Bland-Altman plots for the total score and scores for all domains of the Japanese Western Ontario Rotator Cuff Index (WORC). The bold dashed line indicates the mean difference between the test and retest. The thin dashed lines indicate the limits of agreement

value can be interpreted as a true change in one individual [12, 19]. Thus, it would be important to consider the LOA value for use in individual patients. The minimal clinically important difference, including the LOA, was also relatively high in previous studies; for example, two studies reported values on the reliable change index of 16.9 % [9] and 17.2 % [6], and in another study, the minimum detectable change was 19.1 % in the total score on WORC [11]. Although the values on the reliable change index ranged from 24.7–30.2 % in the five domains in one study [9], values in other studies, including those using the original version of the WORC, were not provided [3, 7, 11]. Unlike the high ICC value observed in the present study, the Bland-Altman plot demonstrated a fixed bias between the results of the first and second tests in the total score and scores for several domains of the Japanese WORC (Fig. 1). Although all subjects indicated no remarkable change in their condition between the test and retest, various physical therapy and prescribed medication interventions were in progress during the study period. Thus, an involuntary influence on the results may have occurred to some extent. Although one previous study mentioned a bias between the test and retest WORC scores, the quantitative values were insufficient [9]. Consequently, we conclude that the

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Japanese WORC demonstrated good reliability for use in a large group, but for use in individual patient assessment, the relatively high values of LOA must be considered. The construct validity of the Japanese WORC was reasonable as compared with that of the other language versions of the WORC [5, 8, 11]. Correlation coefficients are displayed in Table 4; this result was similar to those in previous studies [5, 8, 11]. SF-36 subscales were fairly to moderately correlated with the WORC [8], particularly those related to physical parameters such as bodily pain, role physical, and physical functioning, for which higher correlation coefficients were observed than for the mental parameters [8]. DASH was moderately to highly correlated with WORC [5, 8, 11] because DASH is used for assessment of general disabilities of the upper limbs and includes some common items. This study had several limitations. First, the patient group may not reflect all classes of patients with rotator cuff disorder because all patients were treated in only one hospital. Second, although the test–retest interval was 2–14 days, the optimal interval time has been controversial [23]. In previous studies, the time interval was often chosen with no definite reason for the choice [12]. Thus, in this study, the test and retest were conducted at two consecutive

Reproducibility of Japanese WORC

outpatient visits to minimize therapeutic effects as much as possible. Lastly, because the responsiveness of the Japanese WORC was not tested in this study, it must be tested in future studies. The Brazilian and English versions of the WORC were most responsive to detecting improvement of the three questionnaires [24, 25]. In conclusion, acceptable reliability and validity were demonstrated in this study for the Japanese WORC as an assessment tool for Japanese patients with rotator cuff disorder. In a clinical setting, it could be useful for evaluation of individuals with rotator cuff disorder along with consideration of the relatively high LOA values. Acknowledgments We sincerely thank Dr. S. Griffin for granting us permission to translate and use the WORC and Enago for the English language review.

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14.

Conflict of interest None of the authors has received or will receive any benefit or financial payment from any commercial party related to the subject of this article. 15.

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