Disability and Rehabilitation

ISSN: 0963-8288 (Print) 1464-5165 (Online) Journal homepage: http://www.tandfonline.com/loi/idre20

Cross-cultural adaptation, validity and reliability of the Arabic version of the Lower Extremity Functional Scale Ali H. Alnahdi, Ghada I. Alrashid, Hatem A. Alkhaldi & Ali Z. Aldali To cite this article: Ali H. Alnahdi, Ghada I. Alrashid, Hatem A. Alkhaldi & Ali Z. Aldali (2016) Cross-cultural adaptation, validity and reliability of the Arabic version of the Lower Extremity Functional Scale, Disability and Rehabilitation, 38:9, 897-904, DOI: 10.3109/09638288.2015.1066452 To link to this article: http://dx.doi.org/10.3109/09638288.2015.1066452

Published online: 17 Jul 2015.

Submit your article to this journal

Article views: 61

View related articles

View Crossmark data

Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=idre20 Download by: [Gazi University]

Date: 17 April 2016, At: 09:05

http://informahealthcare.com/dre ISSN 0963-8288 print/ISSN 1464-5165 online Disabil Rehabil, 2016; 38(9): 897–904 ! 2015 Informa UK Ltd. DOI: 10.3109/09638288.2015.1066452

ASSESSMENT PROCEDURES

Cross-cultural adaptation, validity and reliability of the Arabic version of the Lower Extremity Functional Scale Ali H. Alnahdi1, Ghada I. Alrashid2, Hatem A. Alkhaldi2, and Ali Z. Aldali1 Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia and 2Department of Rehabilitation, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia

Downloaded by [Gazi University] at 09:05 17 April 2016

1

Abstract

Keywords

Purpose: The aim was to translate and cross-culturally adapt the Lower Extremity Functional Scale (LEFS) into Arabic language and to examine its measurement properties in patients with musculoskeletal disorders of the lower extremity. Methods: Standard forward and backward translation followed by expert committee review, then preliminary testing was carried out to produce the final Arabic version of LEFS (LEFS-Ar). The test–retest reliability, measurement error, internal consistency and construct validity of the LEFS-Ar were examined in patients with musculoskeletal disorders of the lower extremity (N ¼ 116). Results: The LEFS-Ar had excellent test–retest reliability (ICC2,1 ¼ 0.96). LEFS-Ar standard error of measurement was 3.5 points while the minimal detectable change MDC95 was 9.8 points. LEFS-Ar showed excellent internal consistency with Cronbach’s alpha of 0.95. Parallel analysis and factor analysis showed that LEFS-Ar measures one underlying factor with all items loading heavily on this single factor. LEFS-Ar showed significant positive correlation with patient’s global assessment of function (r ¼ 0.59) and that patients recovering from surgery reported lower LEFS-Ar score compared to patients with no surgery further supporting the construct validity of the LEFS-Ar. Conclusion: LEFS-Ar has excellent internal consistency, test–retest reliability with relatively small measurement error and is a valid measure of activity limitation due to lower extremity musculoskeletal disorders. All these measurement properties of the LEFS-Ar suggest the clinical usefulness of this measure.

Activity limitation, functional limitation, lower extremity, lower limb, Lower Limb Functional Scale, psychometrics History Received 26 November 2014 Revised 17 June 2015 Accepted 23 June 2015 Published online 17 July 2015

ä Implications for Rehabilitation 



The Arabic Lower Extremity Functional Scale (LEFS-Ar) is a reliable and valid measure of activity limitation due to lower extremity musculoskeletal disorders with relatively small measurement error. LEFS-Ar can be used in daily clinical practice and for research purposes to quantify activity limitation in Arabic-speaking individuals with lower extremity musculoskeletal disorders.

Introduction Musculoskeletal disorders of the lower extremity are commonly seen and treated by various health care providers in different clinical setting [1]. They include any disorder in the joints, muscles, or soft tissue of the lower extremity and are known to limit the functional ability of patients [1,2]. Based on the International Classification of Functioning, Disability and Health (ICF) developed by the World Health Organization [3], activity limitation and participation restriction are essential constructs to evaluate and that therapeutic interventions should be aimed to reduce the activity limitation caused by the disorder and to enhance patient’s general participation in societal duties.

Address for correspondence: Dr Ali H. Alnahdi, Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia. Tel: +96614693595. E-mail: [email protected]

The extent of activity limitation and participation restriction caused by the lower extremity disorders can be measured via either performance-based outcome measures or patient-reported outcome measures [4–7]. It is believed that the performancebased and the patient-reported outcome measures do not provide comparable information and that they complement each other [8] and the current clinical practice guidelines for lower extremity musculoskeletal disorders include both types of outcome measures to assess patients’ level of function [4–7]. The Lower Extremity Functional Scale (LEFS) is a regionspecific outcome measure that was designed to assess activity limitations due to musculoskeletal disorders of the lower extremity [9]. LEFS has 20 items each scored on 0–4 Likert scale and the overall score on the scale is produced by summing scores on all items. LEFS score range from 0 to 80 with higher score indicating better functional ability. The developers of LEFS showed that the scale had excellent internal consistency, test–retest reliability, provided evidence of the scale construct validity and showed that the scale is responsive to change in physical function in patients

Downloaded by [Gazi University] at 09:05 17 April 2016

898

A. H. Alnahdi et al.

with various lower extremity musculoskeletal disorders [9]. The validity, reliability and responsiveness of the LEFS has been also established in patients with hip or knee osteoarthritis [10–12], joint arthroplasty [13], anterior knee pain [14], ankle sprain [15] and ankle fracture [16]. Collectively, these resources provide evidence that the LEFS is an excellent patient-reported outcome measure that can be used in clinical practice and for research purposes to assess the level of activity limitation. Due to its clinical usefulness, simplicity and its excellent psychometric properties, LEFS has been translated and Crossculturally adapted into Dutch [17], Italian [18], Persian [19], Greek [20], Brazilian Portuguese [21], Spanish [22] and Taiwan Chinese [23]. Patient-reported outcome measures that assess the functional status of patients with lower extremity disorders are lacking in Arabic language. Therefore, the aim of this study was to translate and culturally adapt the LEFS into Arabic language and to examine the internal consistency, test–retest reliability and construct validity of the Arabic version of LEFS (LEFS-Ar) in patients with musculoskeletal disorders of the lower extremity. We hypothesized that the LEFS-Ar would have good internal consistency, excellent test–retest reliability, and would be a valid measure of lower extremity functional status. The Arabic-version of LEFS will enable clinicians in Arabic-speaking countries to assess the functional status of patients with lower extremity disorders and also will enable them to assess the change in patients’ functional status in response to conservative or surgical interventions.

Disabil Rehabil, 2016; 38(9): 897–904

this meeting, the committee approved the pre-final version of the LEFS-Ar. LEFS-Ar pre-final version was tested for face validity on 20 patients (50% female) with mean age of 38 ± 11.23 years, and BMI of 30.77 ± 6.55 kg/m2. Of these 20 patients, 12 had dysfunctions in the knee and leg, 6 in the ankle and foot, while 2 had dysfunctions in the hip and thigh region. After completing the pre-final version, these 20 patients were interviewed to make sure that they understand all the items of the questionnaire and were asked to give their comments about the questionnaire. Patients indicated the scale instructions were clear and none of the patients had any difficulty understanding the scale instructions or the individual scale items. Patients also indicated that the scale items were relevant to their condition. After testing the pre-final version, the final version of the LEFS-Ar was reached (Appendix). The internal consistency, test–retest reliability, measurement error and construct validity of the final LEFS-Ar were examined in this study. To test the measurement properties of the final LEFS-Ar, all participants were asked to complete the LEFS-Ar, numeric pain rating scale, patient’s global assessment of function. A subset of 30 participants were asked to complete the LEFS-Ar, numeric pain rating scale, patient’s global assessment of function, and global rating of change scale in another session within two week from the first testing session during their regular visits to the physical therapy department to receive physical therapy care. Numeric pain rating scale

Methods Females and males were included in this study if they had lower extremity musculoskeletal disorder, defined as any condition of the joints, muscles, or other soft tissues of the lower extremity and were at least 18 years of age. Subjects were excluded if they were unable to read or speak Arabic, or if they had any neurological dysfunction, neck or back surgery, cardiovascular or pulmonary dysfunctions perceived by the patient as functionally limiting. Subjects were recruited from the physical therapy departments at King Khalid University Hospital and Prince Faisal Sport Medicine Hospital in Riyadh, Saudi Arabia. All participants signed informed consent forms approved by the College of Medicine Human Subjects Review Board at King Saud University prior to participation. Translation and cultural adaption of the LEFS into Arabic language was conducted based on the current guidelines for cultural adaptation of patient-reported outcome measure [24]. Two independent forward translations by native-Arabic speakers were conducted and then were synthesized into one common translated version. This common version was back translated into English by two independent bilingual speakers, who were blinded to the original version of LEFS. All the forward and backward translations were conducted by professional translators who have no medical background. Expert committee including methodologist, health professionals, language professionals and the forward and backward translators was formed to review the translated versions of the scale. Members of the committee were sent the original English version of the scale, the two forward translations, the common forward translation version, and were also sent the two backward translations. Members of the committee were asked to check for semantic equivalence, idiomatic equivalence, experiential equivalence and conceptual equivalence between the Arabic and English versions of the scale and were also asked put their comments in writing. One week later, a meeting was scheduled in which members of the expert committee discussed all the comments they have until reaching consensus on all items of the scale and at the end of

Patients were asked to rate their average pain intensity during the day on a 11-point scale (0 to 10), where 0 represents no pain and 10 represents the most severe pain imaginable. Patients were asked to choose a whole number representing their pain intensity [25]. Higher scores on numeric pain rating scale (NPRS) indicate greater pain intensity. Global assessment of function Patients were asked to rate their perceived functional ability on a scale from 0 to 100 where 0 represents inability to perform any activity of daily living whereas 100 represents the ability to perform all activities of daily living without difficulty. Global rating of change scale Patients were asked to rate the change in their condition since the initial visit in which they completed the LEFS-Ar for the first time. In this study, we used a 15-point global rating of change scale (GRC) ranging from (7) a very great deal worse to (7) a very great deal better [10]. Patients with GRC score of 1 ‘‘tiny bit better, almost the same’’, 0 ‘‘no change’’ and 1 ‘‘tiny bit worse, almost the same’’ were considered unchanged. Statistical analysis Floor and ceiling effects Floor and ceiling effects of the LEFS-Ar were determined by computing the percentage of participants who had the lowest score of the scale, or the highest score of the scale. The scale was considered to have flooring or ceiling effect when more than 15% of the participants had the lowest or highest possible score [17]. Internal consistency and test–retest reliability Cronbach’s alpha was used to examine the internal consistency of LEFS-Ar. Intraclass correlation coefficient model 2,1 for absolute agreement (ICC2,1) [26] was used to examine the test–retest

Arabic Lower Extremity Functional Scale

DOI: 10.3109/09638288.2015.1066452

reliability of the LEFS-Ar. The formula proposed by Bonett [27] was used to estimate the required sample size for the reliability testing:



8Z 2  ð1  ICC Þ2 ð1 þ ðK  1Þ  ICC Þ2   N¼ K ðK  1Þ  CI width2 þ 1



where, Z ¼ Z value associated with the chosen confidence level (1.96 was used for 95% confidence), ICC ¼ estimated ICC (0.90 was used), K ¼ number of observations (2 was used), CI width ¼ confidence interval width (0.2 was used). This method suggested that 15 participants represent an adequate sample size for the test–retest reliability portion of this study.

Downloaded by [Gazi University] at 09:05 17 April 2016

Measurement error Standard error of measurement (SEM) and the Bland–Altman plot were used to examine the measurement error associated with repeated measurement using the LEFS-Ar. SEM was pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi computed using the formula, SEM ¼ SD  1  ICC , where SD was the sample standard deviation and ICC was the test–retest intraclass correlation coefficient [28]. True change in LEFS-Ar that is beyond the measurement error was quantified using the minimal detectable change with 95% confidence (MDC95). MDC95 was computedpffiffiffi using the following formula: MDC95 ¼ SEM  1:96  2 [28]. Construct validity Factor analysis was used to examine the construct validity of the LEFS-Ar. Construct validity will be supported if factor analysis revealed only one major factor underlying the items of LEFS-Ar with loading of all scale items (0.4) on that single factor indicating that the scale measures only one construct, activity limitation [9,17]. Parallel analysis has been suggested as an objective method that help determine the number of factors to be extracted in factor analysis [29]. In this analysis, random data sets similar in size to the original data are generated, and then the 95th percentile of the random data eigenvalues is compared to the actual data eigenvalues. Factors to be extracted are those factors with actual eigenvalue greater than the 95th percentile of the random data eigenvalue. In this study, we used the principle axis factoring method to examine the structure of the LEFS-Ar items and their relations with underlying factors [30]. For parallel analysis, we used O’Connor’s SPSS syntax to generate 1000 normally distributed random data sets [29]. Consensus on the number of participants needed for factor analysis does not exist, but a sample size of 100 seems to be adequate to examine the structure of 20 item questionnaire [31–33]. In addition to factor analysis, we used hypothesis testing method to examine the construct validity of the LEFS-Ar. We hypothesized that LEFS-Ar would show moderate to strong significant positive correlation (r  0.4) with global assessment of function. Pearson’s correlation coefficient was used to examine this hypothesis. Correlation coefficient of 0.4 or above with another outcome measuring similar construct has been suggested to support construct validity [34]. As part of testing the construct validity of LEFS-Ar, we also hypothesized that patients who were in their first 6 months after lower extremity surgical procedure would show lower LEFS-Ar scores compared to patients with lower extremity dysfunction who did not undergo surgery. An independent t-test was used to examine this hypothesis. All analyses were performed with IBM SPSS Statistics 21 (IBM Corp, Armonk, NY). The significance level was set at 0.05.

899

Table 1. Characteristics of participants (N ¼ 116).

Variables Age (years) Female Height (m) Mass (kg) Body Mass Index (BMI) LEFS-Ar NPRS GAF Site Hip and thigh Knee and leg Ankle and foot Type of musculoskeletal disorder Osteoarthritis Meniscal injury Ligament sprain Fracture Plantar fasciitis/heel pain Muscle strain Total joint arthroplasty Arthroscopy Tendinopathy Patellofemoral pain syndrome Non-specific sprain/strain Osteotomy Cyst removal Lower extremity surgery Yes No Educational level Elementary school Middle school High school Undergrauate degree Postgraduate degree Missing

Mean (SD) or N (%) 30.6 52 1.67 77.6 27.5 33.04 4.4 85.5

(10.6) (45) (0.08) (20.2) (7.0) (17.7) (2.2) (22.9)

12 (10.3) 71 (61.2) 33 (28.4) 21 (18.1) 6 (5.2) 24 (20.7) 11(9.5) 15 (12.9) 1 (0.86) 5 (4.3) 2 (1.7) 4 (3.4) 7 (6.03) 17 (14.6) 2 (1.7) 1 (0.86) 26 (22.4) 90 (77.6) 3 7 34 58 12 2

(2.6) (6) (29.3) (50) (10.3) (1.7)

LEFS-Ar ¼ Arabic version of the Lower extremity Functional Scale; NPRS ¼ numeric pain rating scale; GAF ¼ global assessment of function.

Results One hundred and sixteen patients, all Saudi Arabian, with musculoskeletal lower extremity dysfunction participated in this study (Table 1). Translation and cultural adaptation of the LEFSAr was straight forward. The walking two blocks item was translated to walking 250 m in the Arabic version because the phrase ‘‘block’’ is not used in the Arabic culture. The walking for a mile item was also changed to walking for 1.5 km because miles are not used for distances in the Arabic culture. All the 20 patients interviewed during initial stages of the study indicated that all items in the scale were clear, relevant and they did not have any problem in understanding any of the items. Eighty-five patients (73.3%) had no missing items on the LEFS-Ar. 19 patients (16.4%) had one missing items, 7 patients (6%) had 2 missing items, 2 patients (1.7%) had 3 missing items while 3 patients (2.6%) had 4 missing items. Item number 19 (hopping) was the highest missing item and it represents 23% of the missing values followed by item number 6 (squatting) representing 14% of missing values (Table 2). Flooring and ceiling effects None of the patients participated in this study achieved the minimum score or the maximum score on LEFS-Ar. According to

900

A. H. Alnahdi et al.

Disabil Rehabil, 2016; 38(9): 897–904

Downloaded by [Gazi University] at 09:05 17 April 2016

Table 2. LEFS items’ statistics.

Item

Mean

SD

Corrected item to total correlation

Cronbach’s alpha if item deleted

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

2.39 1.86 3.22 3.37 3.16 1.72 2.71 3.04 1.68 2.87 2.63 1.99 2.15 1.64 2.25 1.65 1.11 1.06 1.11 2.72

1.22 1.30 0.98 0.99 1.14 1.42 1.23 1.04 1.30 1.14 1.32 1.31 1.27 1.34 1.43 1.41 1.23 1.26 1.35 1.30

0.75 0.64 0.53 0.63 0.55 0.72 0.63 0.72 0.83 0.69 0.77 0.73 0.77 0.75 0.69 0.77 0.75 0.75 0.69 0.65

0.952 0.953 0.955 0.954 0.955 0.952 0.954 0.952 0.951 0.953 0.951 0.952 0.952 0.952 0.953 0.952 0.952 0.952 0.953 0.953

Any of your usual work, housework or school activities Your usual hobbies, recreational or sporting activities Getting into or out of the bath Walking between rooms Putting on your shoes or socks Squatting Lifting an object, like a bag of groceries from the floor Performing light activities around your home Performing heavy activities around your home Getting into or out of a car Walking 2 blocks Walking a mile Going up or down 10 stairs (about 1 flight of stairs) Standing for 1 h Sitting for 1 h Running on even ground Running on uneven ground Making sharp turns while running fast Hopping Rolling over in bed

Figure 1. Bland–Altman plot of the difference (vertical axis) versus the mean (horizontal axis) for measurements obtained in the first testing session (test) and in the second testing session (retest). The dashed line represents the mean difference between the two testing sessions. The upper and lower thick solid black lines represent the 95% limits of agreement. The upper and lower solid gray lines represent the 95% confidence interval of the mean difference between the two testing sessions. The thin solid black line in the middle represents the line over 0 (the line of equality). Data points for two patients are overlapping.

the criteria we set previously, LEFS-Ar does not seem to have an issue with flooring and ceiling effects. Internal consistency and test–retest reliability For testing the internal consistency of the LEFS-Ar, Cronbach’s alpha was excellent ( ¼ 0.95). With deletion of one item at a time, Cronbach’s alpha ranged from 0.951 to 0.955 (Table 2). The alpha value did not change significantly with the removal of any of the 20 items within the scale. Thirty patients completed the LEFS-Ar in two separate days with mean duration between testing sessions of 8.3 days (range: 1 to 26 days). Eighteen patients out of the 30 reported no change in their functional ability between the two testing sessions according to their response in the GRC. Based on that we used the data from these stable patients (N ¼ 18; 9 male and 9 females) for the ICC computation. LEFS-Ar showed excellent test–retest reliability (ICC2,1 ¼ 0.96; 95% CI; 0.91–0.99).

Measurement error Based on the ICC reliability coefficient, SEM of the LEFS-Ar was 3.5 points, while the MDC95 was 9.8 points. The Bland–Altman plot showed no systematic bias, but rather random error along different levels of the scale (Figure 1). The 95% CI of the mean difference between the second testing session and the first testing session contained the line of equality (zero) indicating the absence of systematic error between testing sessions. Construct validity Parallel analysis indicated that only the first factor had an eigenvalue greater than the 95th percentile of the random data eigenvalue, thus only one factor should be extracted and that the items of LEFS-Ar have one underlying dimension (Figure 2). This factor had an eigenvalue of 10.85 explaining 54.3% of the total variance (Table 3). All items had loadings more than 0.4 on the

Arabic Lower Extremity Functional Scale

Downloaded by [Gazi University] at 09:05 17 April 2016

DOI: 10.3109/09638288.2015.1066452

901

Figure 2. Results of parallel analysis showing the factor number on the horizontal axis and eigenvalue of the vertical axis.

Table 3. LEFS-Ar factor structure.

Table 4. LEFS-Ar factor loading. Initial eigenvalues

Factor

Total

% of Variance

Cumulative %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

10.85 1.79 1.07 0.82 0.73 0.71 0.58 0.55 0.47 0.40 0.33 0.32 0.28 0.24 0.23 0.20 0.16 0.11 0.09 0.07

54.27 8.97 5.35 4.11 3.65 3.56 2.91 2.73 2.36 2.01 1.63 1.59 1.41 1.17 1.13 1.02 0.79 0.55 0.44 0.35

54.27 63.24 68.59 72.70 76.35 79.90 82.81 85.54 87.90 89.91 91.55 93.13 94.55 95.72 96.85 97.87 98.66 99.21 99.65 100.00

first factor with loadings ranging from 0.54 for item number 3 (getting into or out of the bath) to 0.85 for item number 9 (performing heavy activities around your home) (Table 4). The Kaiser–Meyer–Olkin Measure of Sampling Adequacy (KMO) was used to examine the adequacy of the sample used in this study to run factor analysis. KMO statistics value was 0.91 indicating that the sample size used in the factor analysis was sufficient [31]. LEFS-Ar showed significant positive correlation with GAF (r ¼ 0.59, p50.001) and significant negative correlation with NPRS (r ¼ 0.35, p50.001). When comparing post-operative patients who underwent surgery 6 months or before prior to participation in the study to non-operative patients, post-operative patients had lower LEFS-Ar scores (27.3 ± 15.5) compared to the non-operative patients (47.1 ± 16.4) (mean difference ¼ 19.8 points, 95% CI: 12.1, 27.5; p50.001).

LEFS items 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

Any of your usual work, housework or school activities Your usual hobbies, recreational or sporting activities Getting into or out of the bath Walking between rooms Putting on your shoes or socks Squatting Lifting an object, like a bag of groceries from the floor Performing light activities around your home Performing heavy activities around your home Getting into or out of a car Walking 2 blocks Walking a mile Going up or down 10 stairs (about 1 flight of stairs) Standing for 1 h Sitting for 1 h Running on even ground Running on uneven ground Making sharp turns while running fast Hopping Rolling over in bed

Factor 1 loading 0.77 0.66 0.54 0.65 0.56 0.74 0.64 0.74 0.85 0.70 0.80 0.75 0.79 0.77 0.71 0.78 0.77 0.76 0.71 0.66

Discussion This study was conducted to culturally adapt the LEFS into Arabic language and to test its measurement properties including internal consistency, test–retest reliability, measurement error and construct validity. We hypothesized that the LEFS-Ar would have good internal consistency, excellent test–retest reliability, and would be a valid measure of lower extremity functional status. The result of the current study supports these hypotheses. The Arabic version of the LEFS showed excellent internal consistency (Cronbach’s alpha ¼ 0.95) indicating that items within the scale are correlated, homogenous and are not redundant [26,28]. Cronbach’s alpha of the LEFS-Ar did not change with deletion of items one at a time (Table 2) indicating that all items are homogenous and correlated well with each other and that

Downloaded by [Gazi University] at 09:05 17 April 2016

902

A. H. Alnahdi et al.

removal of any item would not improve the internal consistency and homogeneity of the scale. Item statistics (Table 2) also showed good variability around the mean score of all items indicating good performance of these items. Corrected item-to-total correlation (Table 2) represents the correlation between the item with the sum of the rest of items within the scale and it provides an idea about the ability of the item to discriminate between patients on the construct measured. All the 20 items of the LEFS had item-to-total correlation more than 0.4 (range: 0.53–0.83). Item-to-total correlation above 0.4 indicates that this item correlate well with the other items within the scale and this item does help in discriminating between patients [26,34]. However, formal testing of item parameters (difficulty and discrimination) requires implementation of item response theory models [35]. The result of this study supported our hypothesis that the LEFS-Ar would be a reliable measure. LEFS-Ar showed excellent relative test–retest reliability (ICC2,1 ¼ 0.96). The magnitude of this reliability coefficient is higher than that reported for the original English version [9] and the Italian version [18]; and similar to the reliability coefficients reported for the Brazilian [36], Taiwanese [23] and Persian [19] versions of LEFS. To ensure that the condition of patients participating in the retest part of the study did not change between measurements, patients were asked to complete GRC scale. On the GRC, patients reporting 1 (tiny bit worse, almost the same), 0 (no change) and 1 (tiny bit worse, almost the same) were considered unchanged and thus were appropriate for the test–retest reliability testing. Eighteen patients out of the 30 patients (60%) who participated in the test– retest part of the study report no change. Additionally, these patients’ score on the global assessment of function did not change between the testing sessions. Collectively, these informations provide evidence that the status of these patients remained unchanged and thus they were appropriated for the test–retest reliability study. Standard error of measurement (SEM) of the LEFS-Ar was 3.5 points while the MDC95 was 9.8 points. When expressed as a percentage of the average LEFS-Ar score, SEM was 10.6% while MDC95 was 29.3%. Based on their values and their percentage relative to the mean LEFS-Ar score, the measurement error of LEFS-Ar and the MDC presented in this study seems to be clinically applicable. The magnitude of the MDC reported here for the Arabic version of the LEFS is very close to those reported for the original English version and other translated versions. The scale MDC reported to be 9 scale points by the scale developers [9], and it ranges from 7 to 12 scale points in most of the translated versions of the scale [17–19,21,23]. The magnitude of MDC reported in the Spanish version (2.18) seems to differ significantly from that reported by the scale developers and other translated versions of the scale [22] including the Arabic version reported in this manuscript. Factor analysis was used to examine the construct validity of the LEFS-Ar. We hypothesized that LEFS-Ar would have onefactor structure. Exploratory factor analysis revealed one major factor underlying the items of the LEFS-Ar. Parallel analysis performed in this study provided evidence that LEFS-Ar has onefactor structure. All items within the LEFS-Ar loaded significantly on this factor that explains a great proportion of the total variance (54.3%) of the LEFS-Ar. The results of the factor analysis performed in this study support the construct validity of the Arabic version of LEFS and support the notion that the scale measures mainly one underlying construct, activity limitation due to lower extremity musculoskeletal disorders. The underlying structure of the LEFS-Ar is in line with previous reports examining the underlying structure of LEFS. One major factor underlie the items of the original English LEFS [9,37], Dutch

Disabil Rehabil, 2016; 38(9): 897–904

[17], Spanish [22] and Taiwan Chinese LEFS [23]. On the other hand, the authors of the Persian version of the LEFS reported twofactor structure [19]. In addition to the results of factor analysis, the pattern of correlation between LEFS-Ar and GAF also supports the construct validity of the LEFS-Ar. LEFS-Ar was expected to show significant positive correlation with GAF because both LEFS-Ar and GAF measure similar construct, activity limitation, and higher scores on each represents higher level of functioning or less activity limitation. In this study, the LEFS-Ar had moderate correlation with GAF, thus further supporting the construct validity of the LEFS-Ar. For construct validity testing, we also hypothesized that patients recovering from lower extremity surgery would score lower on the LEFS-Ar compared to patient who did not undergo surgery. The results of this study showed that post-operative patients scored significantly lower on the LEFS-Ar compared to the non-operative patients indicating that postoperative patients had lower level of functioning, or high level activity limitation compared to the non-operative patients. The mean difference between the two groups was 19.8 points, which was not only statistically significant but also clinically meaningful since it is twice the value of the scale MDC. This provides another line of evidence supporting the construct validity of the LEFS-Ar. In line with the results of this study, Binkley et al. [9] reported that post-operative patients have significantly lower LEFS scores compared to non-operative patients. The cross-cultural validation of LEFS into Arabic language, implemented in this study, provide clinicians and researchers in Arabic-speaking countries a validated tool that they used to quantify an important health-related domain, activity limitation, in patients with lower extremity musculoskeletal disorders. Using LEFS-Ar would allow clinicians to establish baseline of activity limitation for their patients and also assist clinicians in making the decision whether the patient’s level of activity limitation is reduced, indicating better physical function, as a result of intervention, by comparing the magnitude of change in LEFSAr to the MDC value established in this study. Using LEFS-Ar would also allow researchers in determination of activity limitation at a single time point, the study of the change in activity limitation overtime and also would allow the examination of change in activity limitation as a result of interventions implemented in clinical trials. In this study, LEFS was translated to the classical Arabic language and not to any local dialect of the Arabic language. This was done because translation to the classic Arabic would enhance the use of the scale in all Arabic-speaking countries, which all understand the classic Arabic language contrary to any local dialects understood in one country but not in the others. It should be mentioned here that although LEFS was translated to the classic Arabic language understood in all Arabic-speaking countries, all participants in this study were Saudi Arabian thus recommendations to use the scale in different Arabic countries apart from Saudi Arabia should be preceded by formal testing of the measurement properties of the LEFS-Ar. To say that LEFS-Ar is suitable to be used with patients of different characteristics, LEFS-Ar measurement properties might need to be tested in elderly patients and patients with low educational level because patients with these characteristics were not represented well in this study. This study is not without limitation. The cross-sectional design of the study precluded the examination of the ability of the LEFSAr to measure change (responsiveness) in activity limitation overtime. For LEFS-Ar to be useful in clinical practice, it has to be able to detect change in patient’s status during the course of intervention. In this study, we also did not establish the magnitude of change in the LEFS-Ar considered by patients as important,

DOI: 10.3109/09638288.2015.1066452

minimal clinically important change (MCIC). Determining MCIC of the measure will enhance the clinical relevance of the scale and will help clinicians in deciding whether the change in patient’s score is clinically relevant or not. In summary, this study was carried out to culturally adapt the LEFS in patients with lower extremity musculoskeletal disorders and to examine the measurement properties of the Arabic version of the scale. Adaptation process was smooth with slight changes from the original LEFS. LEFS-Ar was easily understood as reported by patients. The LEFS-Ar had good internal consistency, excellent test–retest reliability, small measurement error and also shown to be a valid measure of activity limitation due to lower extremity musculoskeletal disorders. All these measurement properties of the LEFS-Ar suggest the clinical usefulness of this measure.

Acknowledgements The authors would like to thank all the participants for being part of this study.

Downloaded by [Gazi University] at 09:05 17 April 2016

Declaration of interest The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through the Research Project No. NFG-14-02-15.

References 1. Jacobs JJ. The burden of musculoskeletal diseases in the United States: prevalence, societal and economic cost. Rosemont (IL): American Academy of Orthopaedic Surgeons; 2008. 2. Cross M, Smith E, Hoy D, et al. The global burden of hip and knee osteoarthritis: estimates from the global burden of disease 2010 study. Ann Rheum Dis 2014;73:1323–30. 3. World Health Organization. Internal Classification of Functioning, Disability and Health. Geneva: World Health Organization; 2001. 4. Cibulka MT, White DM, Woehrle J, et al. Hip pain and mobility deficits – hip osteoarthritis: clinical practice guidelines linked to the international classification of functioning, disability, and health from the orthopaedic section of the American Physical Therapy Association. J Orthop Sports Phys Ther 2009;39:A1–25. 5. Logerstedt DS, Snyder-Mackler L, Ritter RC, Axe MJ. Knee pain and mobility impairments: meniscal and articular cartilage lesions. J Orthop Sports Phys Ther 2010;40:A1–35. 6. Logerstedt DS, Snyder-Mackler L, Ritter RC, et al. Knee stability and movement coordination impairments: knee ligament sprain. J Orthop Sports Phys Ther 2010;40:A1–37. 7. McPoil TG, Martin RL, Cornwall MW, et al. Heel pain – plantar fasciitis: clinical practice guildelines linked to the international classification of function, disability, and health from the orthopaedic section of the American Physical Therapy Association. J Orthop Sports Phys Ther 2008;38:A1–18. 8. Stratford PW, Kennedy D, Pagura SM, Gollish JD. The relationship between self-report and performance-related measures: questioning the content validity of timed tests. Arthritis Rheum 2003;49:535–40. 9. Binkley JM, Stratford PW, Lott SA, Riddle DL. The Lower Extremity Functional Scale (LEFS): scale development, measurement properties, and clinical application. North American Orthopaedic Rehabilitation Research Network. Phys Ther 1999;79: 371–83. 10. Williams VJ, Piva SR, Irrgang JJ, et al. Comparison of reliability and responsiveness of patient-reported clinical outcome measures in knee osteoarthritis rehabilitation. J Orthop Sports Phys Ther 2012; 42:716–23. 11. Stratford PW, Kennedy DM, Hanna SE. Condition-specific Western Ontario McMaster Osteoarthritis Index was not superior to regionspecific Lower Extremity Functional Scale at detecting change. J Clin Epidemiol 2004;57:1025–32. 12. Pua YH, Cowan SM, Wrigley TV, Bennell KL. The Lower Extremity Functional Scale could be an alternative to the Western Ontario and McMaster Universities Osteoarthritis Index physical function scale. J Clin Epidemiol 2009;62:1103–11.

Arabic Lower Extremity Functional Scale

903

13. Alnahdi AH, Zeni JA, Snyder-Mackler L. Hip abductor strength reliability and association with physical function after unilateral total knee arthroplasty: a cross-sectional study. Phys Ther 2014;94: 1154–62. 14. Watson CJ, Propps M, Ratner J, et al. Reliability and responsiveness of the lower extremity functional scale and the anterior knee pain scale in patients with anterior knee pain. J Orthop Sports Phys Ther 2005;35:136–46. 15. Naal FD, Impellizzeri FM, Torka S, et al. The German Lower Extremity Functional Scale (LEFS) is reliable, valid and responsive in patients undergoing hip or knee replacement. Qual Life Res 2015; 24:405–10. 16. Lin CW, Moseley AM, Refshauge KM, Bundy AC. The lower extremity functional scale has good clinimetric properties in people with ankle fracture. Phys Ther 2009;89:580–8. 17. Hoogeboom TJ, de Bie RA, den Broeder AA, van den Ende CH. The Dutch Lower Extremity Functional Scale was highly reliable, valid and responsive in individuals with hip/knee osteoarthritis: a validation study. BMC Musculoskelet Disord 2012;13:117. 18. Cacchio A, De Blasis E, Necozione S, et al. The Italian version of the lower extremity functional scale was reliable, valid, and responsive. J Clin Epidemiol 2010;63:550–7. 19. Negahban H, Hessam M, Tabatabaei S, et al. Reliability and validity of the Persian lower extremity functional scale (LEFS) in a heterogeneous sample of outpatients with lower limb musculoskeletal disorders. Disabil Rehabil 2014;36:10–15. 20. Stasi S, Papathanasiou G, Anagnostou M, et al. Lower Extremity Functional Scale (LEFS): cross-cultural adaption into Greek and reliability properties of the instrument. Health Sci J 2012;6: 750–73. 21. Metsavaht L, Leporace G, Riberto M, et al. Translation and crosscultural adaptation of the lower extremity functional scale into a Brazilian Portuguese version and validation on patients with knee injuries. J Orthop Sports Phys Ther 2012;42:932–9. 22. Cruz-Diaz D, Lomas-Vega R, Osuna-Perez MC, et al. The Spanish lower extremity functional scale: a reliable, valid and responsive questionnaire to assess musculoskeletal disorders in the lower extremity. Disabil Rehabil 2014;36:2005–11. 23. Hou WH, Yeh TS, Liang HW. Reliability and validity of the Taiwan Chinese version of the Lower Extremity Functional Scale. J Formos Med Assoc 2014;113:313–20. 24. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine (Phila Pa 1976) 2000;25:3186–91. 25. Hawker GA, Mian S, Kendzerska T, French M. Measures of adult pain: Visual Analog Scale for Pain (VAS Pain), Numeric Rating Scale for Pain (NRS Pain), McGill Pain Questionnaire (MPQ), Short-Form McGill Pain Questionnaire (SF-MPQ), Chronic Pain Grade Scale (CPGS), Short Form-36 Bodily Pain Scale (SF-36 BPS), and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP). Arthritis Care Res (Hoboken) 2011;63: S240–52. 26. de Vet HCW, Terwee CB, Mokkink LB, Knol DL. Measurement in medicine: a practical guide. Cambridge: Cambridge University Press; 2011. 27. Bonett DG. Sample size requirements for estimating intraclass correlations with desired precision. Stat Med 2002;21:1331–5. 28. Portney LG, Watkins MP. Foundations of clinical research: applications to practice. Upper Saddle River: Pearson/Prentice Hall; 2009. 29. O’Connor BP. SPSS and SAS programs for determining the number of components using parallel analysis and velicer’s MAP test. Behav Res Methods Instrum Comput 2000;32:396–402. 30. Warner RM. Applied statistics: from bivariate through multivariate techniques. Thousand Oaks: Sage Publications; 2012. 31. Field A. Discovering statistics using SPSS. London: Sage Publications Ltd; 2009. 32. MacCallum RC, Widaman KF, Zhang SB, Hong SH. Sample size in factor analysis. Psychol Methods 1999;4:84–99. 33. MacCallum RC, Widaman KF, Preacher KJ, Hong S. Sample size in factor analysis: the role of model error. Multivar Behav Res 2001;36: 611–37. 34. Cappelleri JC, Zou KH, Bushmakin AG, et al. Patient-reported outcomes: measurement, implementation and interpretation. Boca Raton: Taylor & Francis; 2013.

904

A. H. Alnahdi et al.

35. Chang CH, Reeve BB. Item response theory and its applications to patient-reported outcomes measurement. Eval Health Prof 2005;28: 264–82. 36. Pereira LM, Dias JM, Mazuquin BF, et al. Translation, cross-cultural adaptation and analysis of the psychometric properties of the lower

Disabil Rehabil, 2016; 38(9): 897–904

extremity functional scale (LEFS): LEFS-BRAZIL. Brazil J Phys Ther 2013;17:272–80. 37. Gabel CP, Melloh M, Burkett B, Michener LA. Lower limb functional index: development and clinimetric properties. Phys Ther 2012;92:98–110.

Downloaded by [Gazi University] at 09:05 17 April 2016

Appendix: Arabic version of the Lower Extremity Functional Scale

Cross-cultural adaptation, validity and reliability of the Arabic version of the Lower Extremity Functional Scale.

The aim was to translate and cross-culturally adapt the Lower Extremity Functional Scale (LEFS) into Arabic language and to examine its measurement pr...
713KB Sizes 0 Downloads 23 Views