http://informahealthcare.com/dre ISSN 0963-8288 print/ISSN 1464-5165 online Disabil Rehabil, Early Online: 1–7 ! 2014 Informa UK Ltd. DOI: 10.3109/09638288.2014.890673
RESEARCH PAPER
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The Spanish lower extremity functional scale: A reliable, valid and responsive questionnaire to assess musculoskeletal disorders in the lower extremity David Cruz-Dı´az1, Rafael Lomas-Vega1, Marı´a Catalina Osuna-Pe´rez1, Fidel Hita-Contreras1,2, A´ngeles Dı´az Ferna´ndez1, and Antonio Martı´nez-Amat1,2 1
Department of Health Sciences, Faculty of Health Sciences, University of Jae´n, Jae´n, Spain and 2Dept Anatomı´a y Embriologı´a, Facultad de Medicina, Institute of Biopathology and Regenerative Medicine (IBIMER), University of Granada, Granada, Spain Abstract
Keywords
Purpose: The Lower Extremity Functional Scale (LEFS) is a widely used questionnaire to evaluate the functional impairment of a patient with a disorder of one or both lower extremities. It also can be used to monitor the patient over time and to evaluate the effectiveness of an intervention. Nevertheless there is no Spanish version of the LEFS, so the aim of this study was the translation and cross-cultural adaption of the Spanish version of the LEFS and to evaluate its psychometrics properties. Methods: The questionnaire was cross cultural adapted into Spanish. The psychometric properties tested in the Spanish version of the LEFS were: internal consistency, test–retest reliability, constructs validity, discriminative validity, responsiveness, concurrent validity and floor and ceiling effects in 132 participants seeking for treatment due to lower extremity dysfunction. Results: The Spanish version of the LEFS had high internal consistency (Cronbach’s ¼ 0.989), test–retest reliability (ICC ¼ 0.998, 95% CI: 0.996–0.999) and presented a high correlation with the SF-36 (36-Item Short-Form Health Survey) especially with the physical function and pain subscales. The construct validity showed a single factor that account for 84.95% of the variance. The standard error of measurement of the Spanish version of the LEFS was 0.88 scale points (95% CI) and the minimal detectable change was 2.18 scale points (95% CI). The sample, collected from five Spanish physical therapy centers, was divided in groups (acute, sub-acute and chronic subjects). Within group changes showed a significant improvement on the LEFS score (p50.001) and effect sizes were large in all conditions. The LEFS allowed to distingue between acute and not acute conditions; for this criterion ROC curve was performed at baseline (area under the curve [AUC] ¼ 0.95). There was no floor or ceiling effects. Conclusions: The Spanish version of the LEFS has been shown to be a valid and reliable tool to assess musculoskeletal dysfunction in the lower extremity that could be used with Spanish speaker population.
Lower extremity functional scale, reliability, Spanish version, validity History Received 16 May 2013 Revised 23 January 2014 Accepted 30 January 2014 Published online 5 March 2014
ä Implications for Rehabilitation
Cross-cultural adaptation of a self-reported questionnaire to evaluate musculoskeletal lower extremity disorders in the Spanish population. To provide Spanish clinicians and physiotherapists a useful tool to assess the lower extremity function. To provide Spanish researchers a valid tool for research on lower extremity function: patient’s improvement due to treatment, compare results obtained between populations, treatment.
Background Public perception of sports has undergone considerable changes in the last few decades. Many adults who were not raised to be active in general sports now perform various types of physical exercise. Physical activity has positive effects on health but it is Address for correspondence: Professor Antonio Martı´nez-Amat, Department of Health Sciences, Faculty of Health Sciences, University of Jae´n, E-23071 Jae´n, Spain. Fax: +34953012141. E-mail: [email protected]
paradoxically associated with an increased number of injures [1], in the same way as certain sports and work activities have been identified as risk factors [2]. It is estimated that between three and five million injuries (especially lower-extremity injuries) occur annually in recreational and competitive athletes in the United States alone [3]. Musculoskeletal disorders in the lower extremities are among the most prevalent health problems in traumatology [4,5] and for this reason more treatment protocols, diagnostic procedures and prevention studies concerning the lower extremities are required. Both medical practitioners
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and researchers have focused on the study of the disabilities associated with the lower extremities but conducting research with a non-English-speaking population can become extremely difficult when the application of a validated measurement tool is required [6]. A generic questionnaire is often used to determine the effectiveness of the intervention [7]. This provides very useful information for clinicians and researchers but a specific measurement tool is needed to evaluate some attributes that are inherent to concrete dysfunctions [8]. Due to the importance of evidence-based health care (defined as doing the right things for the right people at the right time [9]), the Lower Extremity Functional Scale (LEFS) is a valid and reliable instrument to determine the functional status for acute and chronic lower extremity musculoskeletal dysfunction [10]. It is a 20-item questionnaire whose items are ranged in a fivepoint scale ranging from zero to four in order to assess the difficulty in performing different tasks due to physical dysfunction in the lower extremities. The final score of all the items is calculated in a 0–80 score scale, correlated with low and high functional levels respectively [10]. Self-report questionnaires have become a valuable tool to identify the pathology, determine the severity and design the most appropriate treatment. LEFS has shown to be a reliable tool with good psychometric properties, which is able to discriminate between pain and physical functioning where other, such as WOMAC [11] does not. Nevertheless, until recently there has not been a Spanishlanguage version of the LEFS. Instead of making a new questionnaire to evaluate some aspects of health status, cross-culturally adapting a questionnaire is deemed to be a better option [6]. The aim of the present study is to develop the Spanish version of the LEFS and to test its psychometric properties in patients with lower-extremity musculoskeletal dysfunction. The specific objectives of this investigation are to provide preliminary information regarding the group and individual-level reliability, the factor structure and criterion-referenced validity of measures obtained from a Spanish language version of the LEFS.
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Finally, an expert committee was formed by two bilingual experts with medical background, two official translators and one physical therapist was convened to develop a final version by consensus of the previous version of the questionnaire, thus ensuring the proper adaptation to the particular features of the Spanish language and culture and the preservation of the original meaning and structure. After these considerations, the final version was administered to 132 patients and the psychometric properties of the final Spanish version of the LEFS were assessed. Study population and procedures The final Spanish version of the LEFS was administered to a total 132 native Spanish-speaking patients. Inclusion criteria for patients’ recruitment were the same as those applied in the original version [10], with language as the only variation. Individuals referred for physical therapy affected by one side lower extremity musculoskeletal dysfunction (defined as any condition of the joints, muscles or other soft tissues of the lower extremities) and who accept to be enrolled in the present study were recruited by invitation from five Spanish physical therapy and rehabilitation centers. In order to preserve the study population anonymity, patients were identified by their birthday date included in the questionnaire. The study was approved by the Human Ethics Committee of the University of Jae´n and written informed consent was gained from all participants prior to commencing data collection. Inclusion criteria fulfillment was determined by the medical staff of the physical therapy centers. In the first meeting, patients were administered the self-report Spanish version of the LEFS and the SF-36 questionnaires. In order to measure the test–retest reliability, patients completed the LEFS again in an interval time period ranging from two to five days. This short time between test and retest was set in order to reduce the time the patient had to wait to start treatment. The participants of the study did not receive any treatment during this period with the intention of minimizing the possibility of clinical changes. In order to assess responsiveness, a new LEFS measurement was taken after treatment completion; physical therapy treatment consisted of analgesic electrotherapy, joint mobilizations and thermotherapy adapted to each patient’s clinical condition (acute or not acute).
Materials and methods Study design: psychometric evaluation of a cross-sectional survey Cross-cultural adaptation The adaptation of a questionnaire to another language is not limited to perform a literal translation of the original. The culture and peculiarities of the receiving culture must be taken into account in order to preserve the main goals of the tool. If this process is not followed, the validity and reliability of the measure instrument can vary from those of the original version, thus rendering the tool useless for its purpose. The guidelines proposed by Guillemin [12] and Beaton et al. [13] were followed in the cross-cultural adaptation of the LEFS to the Spanish language. Working independently, two native English speakers with a medical background translated the English LEFS into Spanish, one of them with experience in the application of the original questionnaire. The two bilingual experts met with two independent translators without any knowledge about the original questionnaire or health sciences. A single version of the LEFS was developed by consensus between the two versions. This was the previous version of the questionnaire. Back-translation from Spanish into English was performed independently by two other professional bilingual translators who were blinded to the original English version of the LEFS.
Data analysis Data were described with means and standard deviations for continuous variables and frequencies and percentages for categorical variables. To verify the normal distribution of the continuous variables, Kolmogorov–Smirnov test was used. Levene test was used to check the homoscedasticity of the groups. Management and data analysis were performed with the statistical package SPSS for Windows version 17.0 (SPSS Inc, Chicago, IL) and MedCalc 12.5 (MedCalc, Mariakerke, Belgium). The level of statistical significance was set at p50.05. In order to determine the psychometric properties of the Spanish version of the LEFS as an adequate instrument to measure musculoskeletal dysfunction in the lower extremities, floor and ceiling effects, internal consistency, test–retest reliability (Intraclass Correlation Coefficient), concurrent validity, construct validity, responsiveness and discriminative validity were analyzed. Floor and ceiling effects were determined by calculating the number of individuals that got the lowest (0) and highest (80) scores possible and were considered present if more than 15% of the participants achieved the highest or lowest score [14]. Internal consistency of the LEFS was evaluated with Cronbach’s a coefficient and item analysis using the data of baseline evaluation. Internal consistency is considered good when
Cross-cultural adaptation
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DOI: 10.3109/09638288.2014.890673
Cronbach’s a lies between 0.7 and 0.9 [15]. An instrument is considered internally consistent when the items are at least moderately correlated with each other and each item is correlated with the total score ( ¼ 0.70 to 0.95) [13–16]. Test–retest reliability was obtained with Intraclass Correlation Coefficient (ICC) by Shrout and Fleiss [17]. Reliability is considered poor when the ICC is 50.40, moderate between 0.40 and 0.75, substantial between 0.75–0.90 and excellent when ICC 40.90 [17]. Since the acute condition would be experimented rapid change in the clinic situation, only chronic subjects (n ¼ 44) were selected to calculate ICC [10]. Also, to quantify the reliability of the LEFS and to indicate the precision of the score, we determined the Standard Error of Measurement (SEM). The SEM is a representation of measurement error expressed in the same units as the original measurement. We calculated SEM as standard deviation (SD) at baseline (sbase) less the square root of (1Rxx), where Rxx is the test–retest reliability index (ICC) [18]. In addition, we quantified the minimal detectable change at the 95% confidence level p (MDC 95) from the SEM formula as ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi MDS95 ¼ 1:96 base ð1 Rxx Þ, where 1.96 is the z value corresponding to the confidence interval of 95%. The MDC provides a good opportunity to translate the ICC into units of change in the instrument. Concurrent validity. We used the adapted Spanish version of the SF-36 [19]. This is an instrument used to obtain a measure of health status that provides eight scaled scores including physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional and mental health. It also provides two summary measures: physical health (PCS) and mental health (MCS). Each subscale is scored from 0 to 100, with higher scores representing better health status [20]. To evaluate the relation between LEFS and the different dimensions and summary components of SF-36, Pearson correlation coefficients were obtained. This coefficient ranges between 1 and +1 inclusive, where 1 is total positive correlation, 0 is no correlation and 1 is negative correlation between the two variables [21]. Construct validity was assessed by exploratory factorial analysis of the LEFS scores obtained at the first meeting. Principal components analysis was employed with varimax rotation if it was necessary. The number of potential factors was suggested by the number of Eigen values that were 41.0. A scree plot was used to investigate this further using visual estimation. Items on the rotated solution that loaded 40.60 on one factor and 50.40 on any other factor were retained. We chose this rule because it represents a conservative inclusion criterion [22]. This analysis was not tested in the original version of the instrument; however other recent studies have assessed the clinimetric properties of the LEFS and demonstrated a singlefactor structure [23]. Responsiveness refers to the property of a measuring instrument to detect meaningful change over time [24]. Responsiveness was studied with different approaches. We first determined whether the change between baseline LEFS scores and posttreatment scores was statistically significant using Paired t-test for all, acute, sub-acute and chronic subjects. Standardized Response Mean (SRM) [25] was used to analyze the effect size of the change scores between baseline and post-treatment LEFS scores of the sample. The SRM was calculated as the mean change scores divided by the standard deviation of the change scores. Separately, SRM was calculated for all, acute, sub-acute and chronic subjects. The validation study of the LEFS supposed that LEFS scores would be to distingue between acute and not acute conditions [10].
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To measure discriminative validity between acute and not acute conditions, at the first time, t-test was conducted. In the second time, ES (Effect size) and ROC Curves were performed. ES was calculated as the mean difference between acute and not acute (subacute and chronic subjects) divided by the pooled standard deviation of both groups. Separately, ES was calculated making as reference baseline and change scores. ES and SRM were interpreted as follows: 0.2 ¼ small, 0.5 ¼ moderate and 0.8 ¼ greater or large [26]. Separately ROC (Receiver Operating Characteristic) curve analysis was performed using as criterion the acute and not acute condition of the subjects and as variable of responsiveness LEFS scores at baseline.
Results Descriptive statistics From a total of 148 patients recruited, 135 met with the inclusion criteria and 3 patients were excluded because they received medical treatment before re-test. Questionnaires were administered to a total of 132 native Spanish-speaking patients (over 18 years old; 73 male and 59 female). Demographic and clinic characteristics of the sample are presented in Table 1. Attending the evolution of the injury, 75 of the 132 patients showed an acute (53 months), 13 subacute (3 6 months) and 44 chronic (46 months) musculoskeletal dysfunction. On the baseline assessment, acute condition group showed a lower score than the other groups (Table 2). However, on posttreatment assessment, the scores of all groups were more equilibrated. Floor and ceiling effects None of the 132 participants reported the lowest possible score or the highest functional level, implying that the Spanish LEFS has no floor or ceiling effects. Table 1. Demographic and clinic characteristics of the sample (n ¼ 132). Characteristic
Mean
SD
Age (year) Weight (kg) Height (m) BMI (kg/m2)
27.11 70.57 1.72 23.87
6.22 9.24 0.07 2.09
Characteristic
Frequency
Percentage
Injury Osteoarthritis Muscle Strain Ligament Injury Meniscal Injury Patellofemoral Pain Fracture Total Joint Replacement Location Hip Thigh/Knee/Leg Ankle/Foot Type of lesion Articular Soft Tissue Fracture Condition Chronic Subacute Acute
2 29 12 31 29 10 19
1.5% 22.0% 9.1% 23.5% 22.0% 7.6% 14.4%
19 82 31
14.4% 62.1% 23.5%
39 72 19
30.0% 55.4% 14.6%
44 13 75
33.3% 9.8% 56.8%
SD ¼ Standard Deviation; BMI ¼ Body Mass Index.
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Table 2. Mean differences between baseline and post-treatment LEFS scores and acute or not acute subjects. Sample LEFS LEFS LEFS LEFS
Baseline
SD
Post-treatment
SD
Change score
SD
t
p Value
SRM
38.9 25.9 44.5 59.7
19.6 11.7 14.7 11.1
73.6 72.2 72.6 76.3
3.7 2.8 3.1 3.9
34.6 46.3 28.1 16.6
17.8 11.6 13.7 10.1
22.3 34.4 7.4 10.9
50.0001 50.0001 50.0001 50.0001
1.9 4.0 2.0 1.9
Not acute (Chronic and subacute)
SD
Acute
SD
Difference
SE
t
p Value
ES
56.2 19.2
13.5 11.9
25.9 46.3
11.7 11.6
30.4 27.1
2.2 2.1
13.8 13.1
50.0001 50.0001
2.4 2.3
Sample Acute Sub-Acute Chronic
Measurements Pre-treatment scores Change scores
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The values are expressed as Mean and Standard Deviations (SD). LEFS ¼ Lower Extremity Functional Scale. SE ¼ Standard Error. SRM ¼ Standardized Response Mean. ES ¼ Effect Size.
Table 4. Correlation coefficients showed between pretreatment LEFS score and dimensions and summary components of SF-36.
Table 3. Analysis of items.
Items
Corrected item: Cronbach a if total correlation item is deleted
‘‘Today, do you or would you have any difficulty at all with:’’ 1. Any of your usual work, house0.963 0.988 work or school activities 2. Your usual hobbies, recreational or 0.961 0.988 sporting activities 3. Getting into or out of the bath 0.980 0.988 4. Walking between rooms 0.936 0.988 5. Putting on your shoes or socks 0.956 0.988 6. Squatting 0.913 0.988 7. Lifting an object, like a bag of 0.827 0.989 groceries from the floor 8. Performing light activities around 0.956 0.988 your home 9. Performing heavy activities around 0.950 0.988 your home 10. Getting into or out of a car 0.920 0.988 11. Walking 2 blocks 0.902 0.988 12. Walking a mile 0.935 0.988 13. Going up or down 10 stairs 0.966 0.988 (about 1 flight of stairs) 14. Standing for 1 hour 0.918 0.988 15. Sitting for 1 hour 0.672 0.990 16. Running on even ground 0.866 0.989 17. Running on uneven ground 0.872 0.989 18. Making sharp turns while running 0.859 0.989 fast 19. Hopping 0.870 0.989 20. Rolling over in bed 0.941 0.988
Reliability Internal consistency of the LEFS Spanish version was excellent ¼ 0.98. Item analysis showed no significant alpha improvement (Table 3). Test–retest reliability measured with ICC showed a value of 0.998 (95% CI: 0.996 to 0.999). The SEM was 0.88 LEFS points, which led to a minimal detectable change (MDC95) of 2.18 (SD at baseline of 11.1) on a 80-point scale.
LEFS scores
r Coefficient
p Value
0.896 0.800 0.504 0.764 0.744 0.760 0.903 0.657 0.902 0.824
50.001 50.001 50.001 50.001 50.001 50.001 50.001 50.001 50.001 50.001
Physical Functinoning Role Physical Role Emotional Social Functioning Mental Health Vitality Bodily Pain General Health Physical Component Summary Mental Component Summary
Table 5. Factor analysis: Variance explained for the Lower Extremity Functional Scale and factor loadings for each item. Initial eigenvalues Component 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Total 16.891 1.128 0.734 0.443 0.299 0.176 0.122 0.068 0.049 0.043 0.031 0.009 0.004 0.002 0.000 0.000 0.000 0.000 0.000 0.000
% Variance Cumulative, % 84.454 5.641 3.672 2.214 1.496 0.879 0.609 0.341 0.246 0.214 0.156 0.046 0.020 0.011 0.000 0.000 0.000 0.000 0.000 0.000
84.454 90.095 93.768 95.982 97.478 98.357 98.966 99.307 99.554 99.767 99.923 99.969 99.989 100.000 100.000 100.000 100.000 100.000 100.000 100.000
Item number
Factor loadings
Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 Item 9 Item 10 Item 11 Item 12 Item 13 Item 14 Item 15 Item 16 Item 17 Item 18 Item 19 Item 20
0.969 0.967 0.983 0.942 0.962 0.923 0.845 0.962 0.956 0.931 0.910 0.939 0.968 0.925 0.699 0.879 0.880 0.869 0.878 0.949
Construct validity Concurrent validity LEFS Spanish version showed excellent concurrent validity with several scales of SF-36 in the baseline measure. The highest correlation coefficients were obtained with the physical functions and pain subscales. The lowest values of correlation were obtained with General Health and Role Emotional scores, indicating a lower relation of these scores scales with LEFS scores (Table 4).
Principal components analysis yielded one factor that accounted for 84.95% of the variance (Table 5); these results point to a single-factor structure. The factor loadings for each item are also represented in Table 5. As shown in the table, all of the items loaded highly on the factor. Typically, an initial principal components analysis is followed by a rotation that aids in the interpretation of the factors. Rotation in this case was unnecessary since there was only one factor.
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Figure 1. ROC curve making as reference pretest. Classification variable was acute or not acute condition.
Responsiveness The change was statistically significant for all groups and the more it was pronounced, the more acute was the process. The SRM values were large for all groups but higher on more acute condition. The ES between acute and not acute condition were also large at baseline and changes scores (Table 2). On baseline scores, ROC curve analysis showed that AUC was 0.95 (95% CI: 0.90 to 0.98). Sensitivity was 94.67 and specificity was 92.98 for a cut-off point 38 (Figure 1).
Discussion Until now, there was no validated Spanish version of the LEFS, so the aim of this study was to cross-culturally adapt the original version of the LEFS to be used with Spanish-speaking patients with musculoskeletal dysfunction on the lower extremities and evaluate its psychometrics properties. It is of paramount importance to have a measurement tool that allows researchers to compare results in different populations, and the process of crossculturally adapting an instrument that has shown good properties and whose used is extended among clinicians is well documented [12]. Moreover, this guideline to cross-culturally adapt a questionnaire has been successfully used in many health areas [27,28]. Following this standardized protocol to obtain the Spanish version, we did not find any serious difficulties in understanding the technical terms. The only minor modification was the adaptation of the unit length system to the Spanish culture, resulting in the conversion of miles to kilometers in question 12. Preserving the semantic equivalence of the original version, there was no need for grammatical changes during the back translation process. Concerning the psychometric properties of the Spanish LEFS, Cronbach’s a was 0.989, indicating an excellent internal consistency. Compared with others available versions, the results are slightly better than in the original, which showed a Cronbach’s a of 0.968, or the Italian and Dutch versions with a Cronbach’s a of 0.96 and 0.94, respectively [29,30]. Test–retest reliability measured with ICC showed a value of 0.998. This value can also be considered excellent. In similar
Cross-cultural adaptation
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studies, as the Italian version [29], ICC values were 0.89 (95% CI: 0.83–0.91). The Spanish version can thus be considered a reliable tool. Interestingly, the values of the SEM and MDC of the Spanish version of the LEFS were lower than the values reported in prior studies [10,23] (the MDC is approximately 9 scale points in the original version of LEFS). These differences probably were due to the higher reliability in the current study. Higher ICC can also be explained by higher inter-participant variability. The study group had more heterogeneous lower limb pathologies than other studies. Thus, this heterogeneity might have increased variance attributable to participants and, consequently, have decreased the error variance. Factor analysis results indicated a single-factor structure that accounted for 84.95% of the variance (Table 5). All of the items loaded highly on this factor. In the original version of LEFS exploratory factorial analysis showed a one-dimensional structure and other authors who tested it also found a single-factor structure [23]. SF-36 is a generic questionnaire that is widely employed for comparisons with new measures or measurement tools. It could be appreciated that a high correlation exists between LEFS scores and physical function and pain subscales according to the original version of LEFS [10] and Italian version [29]. The use of a questionnaire makes possible to evaluate the patient at the baseline and being able to detect meaningful changes over time. This property is called responsiveness by many authors [24] and it is an essential test to carry out before recommending the use of a measurement tool. To determine the responsiveness of the Spanish LEFS, we compared the scores obtained prior to physical therapy intervention and post-treatment (at the time of discharge). In this interval, it could be observed how the scores changed due to the intervention. Patients with acute conditions demonstrated lower LEFS scores than patients with not acute conditions at the beginning of the treatment, in agreement with the original version of the questionnaire. We expected significant change in the LEFS values of these patients at the end of the treatment. As the original version of LEFS, this approach was based on clinical judgment and on previous work by Westaway et al. [31], whose data suggested that experienced clinicians can make prognoses about patients. Results showed that the effect sizes were large in all conditions but mean within-group differences and SRM values were higher in patients with acute conditions, as we expected. Therefore, the questionnaire is able to detect changes in lower extremity function. Additionally, we conducted Receiver Operating Characteristic curves analysis with LEFS scores at baseline that revealed a large responsiveness for the LEFS. The psychometric properties of the Spanish version of the LEFS were tested in a heterogeneous population. Cacchio et al. [29] successfully carried out a cross-cultural adaptation of the LEFS, pointed out the scarcity of patients with foot conditions in their study population. Thus, the heterogeneity of the population included in the present study can be considered as a positive factor: the original LEFS was developed as a measure that could be used for all kinds of conditions of the lower extremities; for this reason, we do not limit our study to a particular disorder, for example, as Hoogeboom et al. [30] made with hip and knee osteoarthritis. We followed the structure of the original LEFS as a self-report questionnaire instead of an interview process, as was the case of the Italian version. The lack of complex technical terms and the risk of examiner bias were considered when adopting this model. A limitation of our study is the short period of time allowed before retesting. To avoid memory effect, a larger interval between test and retest administration could strengthen our results. Nevertheless, the study population comprised only real
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patients who were seeking for physical therapy assistance and it would, therefore, be unethical to delay their treatment. On the other hand, similar studies have employed the same interval of time [10,25,30]. Another limitation is that only the psychometric properties of the Spanish version of the instrument have been evaluated but not the measurement properties have been calculated for its application to individual patients. Further research could be interesting to assess the ability of the Spanish version of the LEFS to establish functional levels, set goals and track progress and outcome [10]. In addition, the expected maximum value of the Cronbach’s a is 0.90; above this value, it is considered that there is redundancy or duplication. Several items can be measured exactly the same element of a construct; therefore, the redundant items should be deleted. In fact, given the high internal consistency of the Spanish version of the LEFS and its unidimensionality it could lead to future studies to perform a shorter version so that can measure the same way faster and more efficient [32]. Finally, it is to be noted that SRM and effect size (ES) are two measures of responsiveness but their respective definition is slightly different [33]; sometimes the values of SRM have often been interpreted in the same way as ES, however, this may lead to over- or underestimation of effect [34]. In conclusion, the Spanish LEFS is a valid, reliable and responsive measurement tool; it is indicated to properly measure functional impairment in the Spanish population with lowerextremity musculoskeletal dysfunction (see Appendix 1).
Declaration of interest We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated and, if applicable, we certify that all financial and material support for this research (e.g. NIH or NHS grants) and work are clearly identified in the title page of the manuscript. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.
References 1. Haskell WL, Lee I, Pate RR, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Circulation 2007;116:1081–93. 2. Bahr R, Bahr IA. Incidence of acute volleyball injuries: a prospective cohort study of injury mechanisms and risk factors. Scand J Med Sci Sports 1997;7:166–71. 3. National Collegiate Athletic Association. Injury surveillance system. Washington: NCAA; 2002. 4. Bahr R, Reeser JC. Injuries among world-class professional beach volleyball players. The Federation Internationale de Volleyball beach volleyball injury study. Am J Sports Med 2003;31:119–25. 5. Fong DT, Hong Y, Chan L, et al. A systematic review on ankle injury and ankle sprain in sports. Sports Med 2006;37:73–94. 6. Mulero-Portela AL, Colon-Santaella CL, Cruz-Gomez C. Crosscultural adaptation of the disability of arm, shoulder, and hand questionnaire: Spanish for Puerto Rico Version. Int J Rehabil Res 2009;32:287–93. 7. Streiner DL, Norman GR. Health measurement scales. A practical guide to their development and use. Oxford, UK: Oxford Medical Publications; 2003. 8. Bombardier C, Melfi CA, Paul J, et al. Comparison of a generic and a disease-specific measure of pain and physical function after knee replacement surgery. Med Care 1995;33:AS131e44. 9. Muir Gray JA. Evidence based healthcare how to make health policy and management decisions. California: Harcourt Publishers Limited; 2001.
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10. Binkley JM, Stanford 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. 11. Bellamy N. WOMAC osteoarthritis index. A user’s guide. London, Ontario, Canada: University of Western Ontario; 1995. 12. Guillemin F. Cross-cultural adaptation and validation of health status measures. Scand J Rheumatol 1995;24:61–3. 13. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine 2000;15:3186–91. 14. McHorney CA, Tarlov AR. Individual-patient monitoring in clinical practice: are available health status surveys adequate? Qual Life Res 1995;4:293–307. 15. Cronbach LJ. Coefficient alpha and the internal structure of tests. Psychometrika 1951;16:297–334. 16. Ware JE, Snow KK, Kosinski M, Gandek B. SF-36 Health Survey (Manual and Interpretation Guide). Boston, MA: Health Institute, New England Medical Center; 1993. 17. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull 1979;86:420–8. 18. Weir JP. Quantifying test–retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res 2005;19: 231–40. 19. Alonso J, Prieto L, Anto´ JM. The Spanish version of the SF-36 Health Survey (the SF-36 health questionnaire): an instrument for measuring clinical results. Med Clin 1995;104: 771–6. 20. Ware Jr JE, Kosinski M, Bayliss MS, et al. Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study. Med Care 1995;33:AS264–79. 21. Rodgers JL, Nicewander WA. Thirteen ways to look at the correlation coefficient. Am Stat 1988;42:59–66. 22. Cattell RB. The scientific use of factor analysis in behavioral and life sciences. New York, NY: Plenum Press; 1978. 23. Gabel CP, Melloh M, Burkett B, Michener LA. Lower Limb Functional Index. Development and clinimetric properties. Phys Ther 2012;92:98–110. 24. Husted JA, Cook RJ, Farewell VT, Gladman DD. Methods for assessing responsiveness: a critical review and recommendations. J Clin Epidemiol 2000;53:459–68. 25. Liang MH, Fossel AH, Larson MG. Comparison of five health status instruments for orthopaedic evaluation. Med Care 1990;28: 632–42. 26. Cohen J. Statistical power analysis for the behavioral sciences. Hillsdale, NJ: Lawrence Erlbaum Associates; 1988. 27. Victor JF, Ximenes LB, Almeida PC. Cross-cultural adaptation of the Exercise Benefits/Barriers Scale (EBBS) for application in elderly Brazilians: preliminary version. Cad Saude Publica 2008;24: 2852–60. 28. Cruz-Dı´az D, Hita-Contreras F, Lomas-Vega R, et al. Cross-cultural adaptation and validation of the Spanish version of the Cumberland Ankle Instability Tool (CAIT): an instrument to assess unilateral chronic ankle instability. Clin Rheumatol 2013;32:91–8. 29. 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. 30. 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. 31. Westaway M, Stratford PW, Binkley JM. The Patient Specific Functional Scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther 1998;27:331–8. 32. Streiner DL. Starting at the beginning: an introduction to coefficient alpha and internal consistency. J Pers Assess 2003;80:99–103. 33. Angst F, Aeschlimann A, Stucki G. Smallest detectable and minimal clinically important differences of rehabilitation intervention with their implications for required sample sizes using WOMAC and SF36 Quality of life measurement instruments in patients with osteoarthritis of the lower extremities. Arthritis Rheum 2001;45: 384–39. 34. Chui K, Hood E, Klima D. Meaningful change in walking speed. Top Geriatr Rehabil 2012;28:97–103.
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Appendix 1 Spanish version of the LEFS scale. Estimad/a sen¯or/a Estamos interesados en saber si tiene alguna dificultad en alguna de las actividades enumeradas abajo como consecuencia de los problemas de su pierna por los cuales usted esta´ solicitando tratamiento. Por favor, responda a cada una de las actividades. En el dı´a de hoy tiene o tendrı´a alguna dificultad al realizar alguna de las siguientes actividades:
Actividades
Mucha dificultad
Dificultad moderada
Un poco de dificultad
Ninguna dificultad
0 0
1 1
2 2
3
4 4
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2
3 3 3 3
4 4 4 4
0 0
1 1
2 2
3 3
4 4
0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1
2 2 2 2 2 2 2 2 2 2 2
3 3 3 3 3 3 3 3 3 3 3
4 4 4 4 4 4 4 4 4 4 4
1
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Alguna parte de su trabajo habitual, labores dome´sticas o actividades escolares. 2 Suspasatiempos habituales, actividades recreativas y/o deportivas. 3 Al entrar o salir de la ban˜era. 4 Caminando de una habitacio´n a otra 5 Ponie´ndose medias o zapatos. 6 Ponie´ndose en cuclillas. 7 Levantando un objeto por ejemplo una bolsa del supermercado del suelo. 8 Realizando actividades ligeras en su casa. 9 Realizando actividades pesadas en su casa. 10 Subie´ndose o baja´ndose de un coche. 11 Caminando 250 metros. 12 Caminando un kilo´metro. 13 Subiendo o bajando 10 peldan˜os de una escalera. 14 Estando de pie durante una hora. 15 Estando sentado durante una hora. 16 Corriendo sobre terreno peano. 17 Corriendo sobre terreno irregular. 18 Haciendo giros bruscos mientras corre ra´pidamente. 19 Saltando. 20 Al darse la vuelta en la cama. Total columna:
Dificultad extrema o incapaz de realizar la actividad
Puntuacio´n__/80
RESEARCH PAPER
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The Spanish lower extremity functional scale: A reliable, valid and responsive questionnaire to assess musculoskeletal disorders in the lower extremity David Cruz-Dı´az1, Rafael Lomas-Vega1, Marı´a Catalina Osuna-Pe´rez1, Fidel Hita-Contreras1,2, A´ngeles Dı´az Ferna´ndez1, and Antonio Martı´nez-Amat1,2 1
Department of Health Sciences, Faculty of Health Sciences, University of Jae´n, Jae´n, Spain and 2Dept Anatomı´a y Embriologı´a, Facultad de Medicina, Institute of Biopathology and Regenerative Medicine (IBIMER), University of Granada, Granada, Spain Abstract
Keywords
Purpose: The Lower Extremity Functional Scale (LEFS) is a widely used questionnaire to evaluate the functional impairment of a patient with a disorder of one or both lower extremities. It also can be used to monitor the patient over time and to evaluate the effectiveness of an intervention. Nevertheless there is no Spanish version of the LEFS, so the aim of this study was the translation and cross-cultural adaption of the Spanish version of the LEFS and to evaluate its psychometrics properties. Methods: The questionnaire was cross cultural adapted into Spanish. The psychometric properties tested in the Spanish version of the LEFS were: internal consistency, test–retest reliability, constructs validity, discriminative validity, responsiveness, concurrent validity and floor and ceiling effects in 132 participants seeking for treatment due to lower extremity dysfunction. Results: The Spanish version of the LEFS had high internal consistency (Cronbach’s ¼ 0.989), test–retest reliability (ICC ¼ 0.998, 95% CI: 0.996–0.999) and presented a high correlation with the SF-36 (36-Item Short-Form Health Survey) especially with the physical function and pain subscales. The construct validity showed a single factor that account for 84.95% of the variance. The standard error of measurement of the Spanish version of the LEFS was 0.88 scale points (95% CI) and the minimal detectable change was 2.18 scale points (95% CI). The sample, collected from five Spanish physical therapy centers, was divided in groups (acute, sub-acute and chronic subjects). Within group changes showed a significant improvement on the LEFS score (p50.001) and effect sizes were large in all conditions. The LEFS allowed to distingue between acute and not acute conditions; for this criterion ROC curve was performed at baseline (area under the curve [AUC] ¼ 0.95). There was no floor or ceiling effects. Conclusions: The Spanish version of the LEFS has been shown to be a valid and reliable tool to assess musculoskeletal dysfunction in the lower extremity that could be used with Spanish speaker population.
Lower extremity functional scale, reliability, Spanish version, validity History Received 16 May 2013 Revised 23 January 2014 Accepted 30 January 2014 Published online 5 March 2014
ä Implications for Rehabilitation
Cross-cultural adaptation of a self-reported questionnaire to evaluate musculoskeletal lower extremity disorders in the Spanish population. To provide Spanish clinicians and physiotherapists a useful tool to assess the lower extremity function. To provide Spanish researchers a valid tool for research on lower extremity function: patient’s improvement due to treatment, compare results obtained between populations, treatment.
Background Public perception of sports has undergone considerable changes in the last few decades. Many adults who were not raised to be active in general sports now perform various types of physical exercise. Physical activity has positive effects on health but it is Address for correspondence: Professor Antonio Martı´nez-Amat, Department of Health Sciences, Faculty of Health Sciences, University of Jae´n, E-23071 Jae´n, Spain. Fax: +34953012141. E-mail: [email protected]
paradoxically associated with an increased number of injures [1], in the same way as certain sports and work activities have been identified as risk factors [2]. It is estimated that between three and five million injuries (especially lower-extremity injuries) occur annually in recreational and competitive athletes in the United States alone [3]. Musculoskeletal disorders in the lower extremities are among the most prevalent health problems in traumatology [4,5] and for this reason more treatment protocols, diagnostic procedures and prevention studies concerning the lower extremities are required. Both medical practitioners
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and researchers have focused on the study of the disabilities associated with the lower extremities but conducting research with a non-English-speaking population can become extremely difficult when the application of a validated measurement tool is required [6]. A generic questionnaire is often used to determine the effectiveness of the intervention [7]. This provides very useful information for clinicians and researchers but a specific measurement tool is needed to evaluate some attributes that are inherent to concrete dysfunctions [8]. Due to the importance of evidence-based health care (defined as doing the right things for the right people at the right time [9]), the Lower Extremity Functional Scale (LEFS) is a valid and reliable instrument to determine the functional status for acute and chronic lower extremity musculoskeletal dysfunction [10]. It is a 20-item questionnaire whose items are ranged in a fivepoint scale ranging from zero to four in order to assess the difficulty in performing different tasks due to physical dysfunction in the lower extremities. The final score of all the items is calculated in a 0–80 score scale, correlated with low and high functional levels respectively [10]. Self-report questionnaires have become a valuable tool to identify the pathology, determine the severity and design the most appropriate treatment. LEFS has shown to be a reliable tool with good psychometric properties, which is able to discriminate between pain and physical functioning where other, such as WOMAC [11] does not. Nevertheless, until recently there has not been a Spanishlanguage version of the LEFS. Instead of making a new questionnaire to evaluate some aspects of health status, cross-culturally adapting a questionnaire is deemed to be a better option [6]. The aim of the present study is to develop the Spanish version of the LEFS and to test its psychometric properties in patients with lower-extremity musculoskeletal dysfunction. The specific objectives of this investigation are to provide preliminary information regarding the group and individual-level reliability, the factor structure and criterion-referenced validity of measures obtained from a Spanish language version of the LEFS.
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Finally, an expert committee was formed by two bilingual experts with medical background, two official translators and one physical therapist was convened to develop a final version by consensus of the previous version of the questionnaire, thus ensuring the proper adaptation to the particular features of the Spanish language and culture and the preservation of the original meaning and structure. After these considerations, the final version was administered to 132 patients and the psychometric properties of the final Spanish version of the LEFS were assessed. Study population and procedures The final Spanish version of the LEFS was administered to a total 132 native Spanish-speaking patients. Inclusion criteria for patients’ recruitment were the same as those applied in the original version [10], with language as the only variation. Individuals referred for physical therapy affected by one side lower extremity musculoskeletal dysfunction (defined as any condition of the joints, muscles or other soft tissues of the lower extremities) and who accept to be enrolled in the present study were recruited by invitation from five Spanish physical therapy and rehabilitation centers. In order to preserve the study population anonymity, patients were identified by their birthday date included in the questionnaire. The study was approved by the Human Ethics Committee of the University of Jae´n and written informed consent was gained from all participants prior to commencing data collection. Inclusion criteria fulfillment was determined by the medical staff of the physical therapy centers. In the first meeting, patients were administered the self-report Spanish version of the LEFS and the SF-36 questionnaires. In order to measure the test–retest reliability, patients completed the LEFS again in an interval time period ranging from two to five days. This short time between test and retest was set in order to reduce the time the patient had to wait to start treatment. The participants of the study did not receive any treatment during this period with the intention of minimizing the possibility of clinical changes. In order to assess responsiveness, a new LEFS measurement was taken after treatment completion; physical therapy treatment consisted of analgesic electrotherapy, joint mobilizations and thermotherapy adapted to each patient’s clinical condition (acute or not acute).
Materials and methods Study design: psychometric evaluation of a cross-sectional survey Cross-cultural adaptation The adaptation of a questionnaire to another language is not limited to perform a literal translation of the original. The culture and peculiarities of the receiving culture must be taken into account in order to preserve the main goals of the tool. If this process is not followed, the validity and reliability of the measure instrument can vary from those of the original version, thus rendering the tool useless for its purpose. The guidelines proposed by Guillemin [12] and Beaton et al. [13] were followed in the cross-cultural adaptation of the LEFS to the Spanish language. Working independently, two native English speakers with a medical background translated the English LEFS into Spanish, one of them with experience in the application of the original questionnaire. The two bilingual experts met with two independent translators without any knowledge about the original questionnaire or health sciences. A single version of the LEFS was developed by consensus between the two versions. This was the previous version of the questionnaire. Back-translation from Spanish into English was performed independently by two other professional bilingual translators who were blinded to the original English version of the LEFS.
Data analysis Data were described with means and standard deviations for continuous variables and frequencies and percentages for categorical variables. To verify the normal distribution of the continuous variables, Kolmogorov–Smirnov test was used. Levene test was used to check the homoscedasticity of the groups. Management and data analysis were performed with the statistical package SPSS for Windows version 17.0 (SPSS Inc, Chicago, IL) and MedCalc 12.5 (MedCalc, Mariakerke, Belgium). The level of statistical significance was set at p50.05. In order to determine the psychometric properties of the Spanish version of the LEFS as an adequate instrument to measure musculoskeletal dysfunction in the lower extremities, floor and ceiling effects, internal consistency, test–retest reliability (Intraclass Correlation Coefficient), concurrent validity, construct validity, responsiveness and discriminative validity were analyzed. Floor and ceiling effects were determined by calculating the number of individuals that got the lowest (0) and highest (80) scores possible and were considered present if more than 15% of the participants achieved the highest or lowest score [14]. Internal consistency of the LEFS was evaluated with Cronbach’s a coefficient and item analysis using the data of baseline evaluation. Internal consistency is considered good when
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DOI: 10.3109/09638288.2014.890673
Cronbach’s a lies between 0.7 and 0.9 [15]. An instrument is considered internally consistent when the items are at least moderately correlated with each other and each item is correlated with the total score ( ¼ 0.70 to 0.95) [13–16]. Test–retest reliability was obtained with Intraclass Correlation Coefficient (ICC) by Shrout and Fleiss [17]. Reliability is considered poor when the ICC is 50.40, moderate between 0.40 and 0.75, substantial between 0.75–0.90 and excellent when ICC 40.90 [17]. Since the acute condition would be experimented rapid change in the clinic situation, only chronic subjects (n ¼ 44) were selected to calculate ICC [10]. Also, to quantify the reliability of the LEFS and to indicate the precision of the score, we determined the Standard Error of Measurement (SEM). The SEM is a representation of measurement error expressed in the same units as the original measurement. We calculated SEM as standard deviation (SD) at baseline (sbase) less the square root of (1Rxx), where Rxx is the test–retest reliability index (ICC) [18]. In addition, we quantified the minimal detectable change at the 95% confidence level p (MDC 95) from the SEM formula as ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi MDS95 ¼ 1:96 base ð1 Rxx Þ, where 1.96 is the z value corresponding to the confidence interval of 95%. The MDC provides a good opportunity to translate the ICC into units of change in the instrument. Concurrent validity. We used the adapted Spanish version of the SF-36 [19]. This is an instrument used to obtain a measure of health status that provides eight scaled scores including physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional and mental health. It also provides two summary measures: physical health (PCS) and mental health (MCS). Each subscale is scored from 0 to 100, with higher scores representing better health status [20]. To evaluate the relation between LEFS and the different dimensions and summary components of SF-36, Pearson correlation coefficients were obtained. This coefficient ranges between 1 and +1 inclusive, where 1 is total positive correlation, 0 is no correlation and 1 is negative correlation between the two variables [21]. Construct validity was assessed by exploratory factorial analysis of the LEFS scores obtained at the first meeting. Principal components analysis was employed with varimax rotation if it was necessary. The number of potential factors was suggested by the number of Eigen values that were 41.0. A scree plot was used to investigate this further using visual estimation. Items on the rotated solution that loaded 40.60 on one factor and 50.40 on any other factor were retained. We chose this rule because it represents a conservative inclusion criterion [22]. This analysis was not tested in the original version of the instrument; however other recent studies have assessed the clinimetric properties of the LEFS and demonstrated a singlefactor structure [23]. Responsiveness refers to the property of a measuring instrument to detect meaningful change over time [24]. Responsiveness was studied with different approaches. We first determined whether the change between baseline LEFS scores and posttreatment scores was statistically significant using Paired t-test for all, acute, sub-acute and chronic subjects. Standardized Response Mean (SRM) [25] was used to analyze the effect size of the change scores between baseline and post-treatment LEFS scores of the sample. The SRM was calculated as the mean change scores divided by the standard deviation of the change scores. Separately, SRM was calculated for all, acute, sub-acute and chronic subjects. The validation study of the LEFS supposed that LEFS scores would be to distingue between acute and not acute conditions [10].
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To measure discriminative validity between acute and not acute conditions, at the first time, t-test was conducted. In the second time, ES (Effect size) and ROC Curves were performed. ES was calculated as the mean difference between acute and not acute (subacute and chronic subjects) divided by the pooled standard deviation of both groups. Separately, ES was calculated making as reference baseline and change scores. ES and SRM were interpreted as follows: 0.2 ¼ small, 0.5 ¼ moderate and 0.8 ¼ greater or large [26]. Separately ROC (Receiver Operating Characteristic) curve analysis was performed using as criterion the acute and not acute condition of the subjects and as variable of responsiveness LEFS scores at baseline.
Results Descriptive statistics From a total of 148 patients recruited, 135 met with the inclusion criteria and 3 patients were excluded because they received medical treatment before re-test. Questionnaires were administered to a total of 132 native Spanish-speaking patients (over 18 years old; 73 male and 59 female). Demographic and clinic characteristics of the sample are presented in Table 1. Attending the evolution of the injury, 75 of the 132 patients showed an acute (53 months), 13 subacute (3 6 months) and 44 chronic (46 months) musculoskeletal dysfunction. On the baseline assessment, acute condition group showed a lower score than the other groups (Table 2). However, on posttreatment assessment, the scores of all groups were more equilibrated. Floor and ceiling effects None of the 132 participants reported the lowest possible score or the highest functional level, implying that the Spanish LEFS has no floor or ceiling effects. Table 1. Demographic and clinic characteristics of the sample (n ¼ 132). Characteristic
Mean
SD
Age (year) Weight (kg) Height (m) BMI (kg/m2)
27.11 70.57 1.72 23.87
6.22 9.24 0.07 2.09
Characteristic
Frequency
Percentage
Injury Osteoarthritis Muscle Strain Ligament Injury Meniscal Injury Patellofemoral Pain Fracture Total Joint Replacement Location Hip Thigh/Knee/Leg Ankle/Foot Type of lesion Articular Soft Tissue Fracture Condition Chronic Subacute Acute
2 29 12 31 29 10 19
1.5% 22.0% 9.1% 23.5% 22.0% 7.6% 14.4%
19 82 31
14.4% 62.1% 23.5%
39 72 19
30.0% 55.4% 14.6%
44 13 75
33.3% 9.8% 56.8%
SD ¼ Standard Deviation; BMI ¼ Body Mass Index.
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Table 2. Mean differences between baseline and post-treatment LEFS scores and acute or not acute subjects. Sample LEFS LEFS LEFS LEFS
Baseline
SD
Post-treatment
SD
Change score
SD
t
p Value
SRM
38.9 25.9 44.5 59.7
19.6 11.7 14.7 11.1
73.6 72.2 72.6 76.3
3.7 2.8 3.1 3.9
34.6 46.3 28.1 16.6
17.8 11.6 13.7 10.1
22.3 34.4 7.4 10.9
50.0001 50.0001 50.0001 50.0001
1.9 4.0 2.0 1.9
Not acute (Chronic and subacute)
SD
Acute
SD
Difference
SE
t
p Value
ES
56.2 19.2
13.5 11.9
25.9 46.3
11.7 11.6
30.4 27.1
2.2 2.1
13.8 13.1
50.0001 50.0001
2.4 2.3
Sample Acute Sub-Acute Chronic
Measurements Pre-treatment scores Change scores
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The values are expressed as Mean and Standard Deviations (SD). LEFS ¼ Lower Extremity Functional Scale. SE ¼ Standard Error. SRM ¼ Standardized Response Mean. ES ¼ Effect Size.
Table 4. Correlation coefficients showed between pretreatment LEFS score and dimensions and summary components of SF-36.
Table 3. Analysis of items.
Items
Corrected item: Cronbach a if total correlation item is deleted
‘‘Today, do you or would you have any difficulty at all with:’’ 1. Any of your usual work, house0.963 0.988 work or school activities 2. Your usual hobbies, recreational or 0.961 0.988 sporting activities 3. Getting into or out of the bath 0.980 0.988 4. Walking between rooms 0.936 0.988 5. Putting on your shoes or socks 0.956 0.988 6. Squatting 0.913 0.988 7. Lifting an object, like a bag of 0.827 0.989 groceries from the floor 8. Performing light activities around 0.956 0.988 your home 9. Performing heavy activities around 0.950 0.988 your home 10. Getting into or out of a car 0.920 0.988 11. Walking 2 blocks 0.902 0.988 12. Walking a mile 0.935 0.988 13. Going up or down 10 stairs 0.966 0.988 (about 1 flight of stairs) 14. Standing for 1 hour 0.918 0.988 15. Sitting for 1 hour 0.672 0.990 16. Running on even ground 0.866 0.989 17. Running on uneven ground 0.872 0.989 18. Making sharp turns while running 0.859 0.989 fast 19. Hopping 0.870 0.989 20. Rolling over in bed 0.941 0.988
Reliability Internal consistency of the LEFS Spanish version was excellent ¼ 0.98. Item analysis showed no significant alpha improvement (Table 3). Test–retest reliability measured with ICC showed a value of 0.998 (95% CI: 0.996 to 0.999). The SEM was 0.88 LEFS points, which led to a minimal detectable change (MDC95) of 2.18 (SD at baseline of 11.1) on a 80-point scale.
LEFS scores
r Coefficient
p Value
0.896 0.800 0.504 0.764 0.744 0.760 0.903 0.657 0.902 0.824
50.001 50.001 50.001 50.001 50.001 50.001 50.001 50.001 50.001 50.001
Physical Functinoning Role Physical Role Emotional Social Functioning Mental Health Vitality Bodily Pain General Health Physical Component Summary Mental Component Summary
Table 5. Factor analysis: Variance explained for the Lower Extremity Functional Scale and factor loadings for each item. Initial eigenvalues Component 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Total 16.891 1.128 0.734 0.443 0.299 0.176 0.122 0.068 0.049 0.043 0.031 0.009 0.004 0.002 0.000 0.000 0.000 0.000 0.000 0.000
% Variance Cumulative, % 84.454 5.641 3.672 2.214 1.496 0.879 0.609 0.341 0.246 0.214 0.156 0.046 0.020 0.011 0.000 0.000 0.000 0.000 0.000 0.000
84.454 90.095 93.768 95.982 97.478 98.357 98.966 99.307 99.554 99.767 99.923 99.969 99.989 100.000 100.000 100.000 100.000 100.000 100.000 100.000
Item number
Factor loadings
Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 Item 9 Item 10 Item 11 Item 12 Item 13 Item 14 Item 15 Item 16 Item 17 Item 18 Item 19 Item 20
0.969 0.967 0.983 0.942 0.962 0.923 0.845 0.962 0.956 0.931 0.910 0.939 0.968 0.925 0.699 0.879 0.880 0.869 0.878 0.949
Construct validity Concurrent validity LEFS Spanish version showed excellent concurrent validity with several scales of SF-36 in the baseline measure. The highest correlation coefficients were obtained with the physical functions and pain subscales. The lowest values of correlation were obtained with General Health and Role Emotional scores, indicating a lower relation of these scores scales with LEFS scores (Table 4).
Principal components analysis yielded one factor that accounted for 84.95% of the variance (Table 5); these results point to a single-factor structure. The factor loadings for each item are also represented in Table 5. As shown in the table, all of the items loaded highly on the factor. Typically, an initial principal components analysis is followed by a rotation that aids in the interpretation of the factors. Rotation in this case was unnecessary since there was only one factor.
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Figure 1. ROC curve making as reference pretest. Classification variable was acute or not acute condition.
Responsiveness The change was statistically significant for all groups and the more it was pronounced, the more acute was the process. The SRM values were large for all groups but higher on more acute condition. The ES between acute and not acute condition were also large at baseline and changes scores (Table 2). On baseline scores, ROC curve analysis showed that AUC was 0.95 (95% CI: 0.90 to 0.98). Sensitivity was 94.67 and specificity was 92.98 for a cut-off point 38 (Figure 1).
Discussion Until now, there was no validated Spanish version of the LEFS, so the aim of this study was to cross-culturally adapt the original version of the LEFS to be used with Spanish-speaking patients with musculoskeletal dysfunction on the lower extremities and evaluate its psychometrics properties. It is of paramount importance to have a measurement tool that allows researchers to compare results in different populations, and the process of crossculturally adapting an instrument that has shown good properties and whose used is extended among clinicians is well documented [12]. Moreover, this guideline to cross-culturally adapt a questionnaire has been successfully used in many health areas [27,28]. Following this standardized protocol to obtain the Spanish version, we did not find any serious difficulties in understanding the technical terms. The only minor modification was the adaptation of the unit length system to the Spanish culture, resulting in the conversion of miles to kilometers in question 12. Preserving the semantic equivalence of the original version, there was no need for grammatical changes during the back translation process. Concerning the psychometric properties of the Spanish LEFS, Cronbach’s a was 0.989, indicating an excellent internal consistency. Compared with others available versions, the results are slightly better than in the original, which showed a Cronbach’s a of 0.968, or the Italian and Dutch versions with a Cronbach’s a of 0.96 and 0.94, respectively [29,30]. Test–retest reliability measured with ICC showed a value of 0.998. This value can also be considered excellent. In similar
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studies, as the Italian version [29], ICC values were 0.89 (95% CI: 0.83–0.91). The Spanish version can thus be considered a reliable tool. Interestingly, the values of the SEM and MDC of the Spanish version of the LEFS were lower than the values reported in prior studies [10,23] (the MDC is approximately 9 scale points in the original version of LEFS). These differences probably were due to the higher reliability in the current study. Higher ICC can also be explained by higher inter-participant variability. The study group had more heterogeneous lower limb pathologies than other studies. Thus, this heterogeneity might have increased variance attributable to participants and, consequently, have decreased the error variance. Factor analysis results indicated a single-factor structure that accounted for 84.95% of the variance (Table 5). All of the items loaded highly on this factor. In the original version of LEFS exploratory factorial analysis showed a one-dimensional structure and other authors who tested it also found a single-factor structure [23]. SF-36 is a generic questionnaire that is widely employed for comparisons with new measures or measurement tools. It could be appreciated that a high correlation exists between LEFS scores and physical function and pain subscales according to the original version of LEFS [10] and Italian version [29]. The use of a questionnaire makes possible to evaluate the patient at the baseline and being able to detect meaningful changes over time. This property is called responsiveness by many authors [24] and it is an essential test to carry out before recommending the use of a measurement tool. To determine the responsiveness of the Spanish LEFS, we compared the scores obtained prior to physical therapy intervention and post-treatment (at the time of discharge). In this interval, it could be observed how the scores changed due to the intervention. Patients with acute conditions demonstrated lower LEFS scores than patients with not acute conditions at the beginning of the treatment, in agreement with the original version of the questionnaire. We expected significant change in the LEFS values of these patients at the end of the treatment. As the original version of LEFS, this approach was based on clinical judgment and on previous work by Westaway et al. [31], whose data suggested that experienced clinicians can make prognoses about patients. Results showed that the effect sizes were large in all conditions but mean within-group differences and SRM values were higher in patients with acute conditions, as we expected. Therefore, the questionnaire is able to detect changes in lower extremity function. Additionally, we conducted Receiver Operating Characteristic curves analysis with LEFS scores at baseline that revealed a large responsiveness for the LEFS. The psychometric properties of the Spanish version of the LEFS were tested in a heterogeneous population. Cacchio et al. [29] successfully carried out a cross-cultural adaptation of the LEFS, pointed out the scarcity of patients with foot conditions in their study population. Thus, the heterogeneity of the population included in the present study can be considered as a positive factor: the original LEFS was developed as a measure that could be used for all kinds of conditions of the lower extremities; for this reason, we do not limit our study to a particular disorder, for example, as Hoogeboom et al. [30] made with hip and knee osteoarthritis. We followed the structure of the original LEFS as a self-report questionnaire instead of an interview process, as was the case of the Italian version. The lack of complex technical terms and the risk of examiner bias were considered when adopting this model. A limitation of our study is the short period of time allowed before retesting. To avoid memory effect, a larger interval between test and retest administration could strengthen our results. Nevertheless, the study population comprised only real
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D. Cruz-Dı´az et al.
patients who were seeking for physical therapy assistance and it would, therefore, be unethical to delay their treatment. On the other hand, similar studies have employed the same interval of time [10,25,30]. Another limitation is that only the psychometric properties of the Spanish version of the instrument have been evaluated but not the measurement properties have been calculated for its application to individual patients. Further research could be interesting to assess the ability of the Spanish version of the LEFS to establish functional levels, set goals and track progress and outcome [10]. In addition, the expected maximum value of the Cronbach’s a is 0.90; above this value, it is considered that there is redundancy or duplication. Several items can be measured exactly the same element of a construct; therefore, the redundant items should be deleted. In fact, given the high internal consistency of the Spanish version of the LEFS and its unidimensionality it could lead to future studies to perform a shorter version so that can measure the same way faster and more efficient [32]. Finally, it is to be noted that SRM and effect size (ES) are two measures of responsiveness but their respective definition is slightly different [33]; sometimes the values of SRM have often been interpreted in the same way as ES, however, this may lead to over- or underestimation of effect [34]. In conclusion, the Spanish LEFS is a valid, reliable and responsive measurement tool; it is indicated to properly measure functional impairment in the Spanish population with lowerextremity musculoskeletal dysfunction (see Appendix 1).
Declaration of interest We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated and, if applicable, we certify that all financial and material support for this research (e.g. NIH or NHS grants) and work are clearly identified in the title page of the manuscript. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.
References 1. Haskell WL, Lee I, Pate RR, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Circulation 2007;116:1081–93. 2. Bahr R, Bahr IA. Incidence of acute volleyball injuries: a prospective cohort study of injury mechanisms and risk factors. Scand J Med Sci Sports 1997;7:166–71. 3. National Collegiate Athletic Association. Injury surveillance system. Washington: NCAA; 2002. 4. Bahr R, Reeser JC. Injuries among world-class professional beach volleyball players. The Federation Internationale de Volleyball beach volleyball injury study. Am J Sports Med 2003;31:119–25. 5. Fong DT, Hong Y, Chan L, et al. A systematic review on ankle injury and ankle sprain in sports. Sports Med 2006;37:73–94. 6. Mulero-Portela AL, Colon-Santaella CL, Cruz-Gomez C. Crosscultural adaptation of the disability of arm, shoulder, and hand questionnaire: Spanish for Puerto Rico Version. Int J Rehabil Res 2009;32:287–93. 7. Streiner DL, Norman GR. Health measurement scales. A practical guide to their development and use. Oxford, UK: Oxford Medical Publications; 2003. 8. Bombardier C, Melfi CA, Paul J, et al. Comparison of a generic and a disease-specific measure of pain and physical function after knee replacement surgery. Med Care 1995;33:AS131e44. 9. Muir Gray JA. Evidence based healthcare how to make health policy and management decisions. California: Harcourt Publishers Limited; 2001.
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10. Binkley JM, Stanford 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. 11. Bellamy N. WOMAC osteoarthritis index. A user’s guide. London, Ontario, Canada: University of Western Ontario; 1995. 12. Guillemin F. Cross-cultural adaptation and validation of health status measures. Scand J Rheumatol 1995;24:61–3. 13. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine 2000;15:3186–91. 14. McHorney CA, Tarlov AR. Individual-patient monitoring in clinical practice: are available health status surveys adequate? Qual Life Res 1995;4:293–307. 15. Cronbach LJ. Coefficient alpha and the internal structure of tests. Psychometrika 1951;16:297–334. 16. Ware JE, Snow KK, Kosinski M, Gandek B. SF-36 Health Survey (Manual and Interpretation Guide). Boston, MA: Health Institute, New England Medical Center; 1993. 17. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull 1979;86:420–8. 18. Weir JP. Quantifying test–retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res 2005;19: 231–40. 19. Alonso J, Prieto L, Anto´ JM. The Spanish version of the SF-36 Health Survey (the SF-36 health questionnaire): an instrument for measuring clinical results. Med Clin 1995;104: 771–6. 20. Ware Jr JE, Kosinski M, Bayliss MS, et al. Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study. Med Care 1995;33:AS264–79. 21. Rodgers JL, Nicewander WA. Thirteen ways to look at the correlation coefficient. Am Stat 1988;42:59–66. 22. Cattell RB. The scientific use of factor analysis in behavioral and life sciences. New York, NY: Plenum Press; 1978. 23. Gabel CP, Melloh M, Burkett B, Michener LA. Lower Limb Functional Index. Development and clinimetric properties. Phys Ther 2012;92:98–110. 24. Husted JA, Cook RJ, Farewell VT, Gladman DD. Methods for assessing responsiveness: a critical review and recommendations. J Clin Epidemiol 2000;53:459–68. 25. Liang MH, Fossel AH, Larson MG. Comparison of five health status instruments for orthopaedic evaluation. Med Care 1990;28: 632–42. 26. Cohen J. Statistical power analysis for the behavioral sciences. Hillsdale, NJ: Lawrence Erlbaum Associates; 1988. 27. Victor JF, Ximenes LB, Almeida PC. Cross-cultural adaptation of the Exercise Benefits/Barriers Scale (EBBS) for application in elderly Brazilians: preliminary version. Cad Saude Publica 2008;24: 2852–60. 28. Cruz-Dı´az D, Hita-Contreras F, Lomas-Vega R, et al. Cross-cultural adaptation and validation of the Spanish version of the Cumberland Ankle Instability Tool (CAIT): an instrument to assess unilateral chronic ankle instability. Clin Rheumatol 2013;32:91–8. 29. 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. 30. 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. 31. Westaway M, Stratford PW, Binkley JM. The Patient Specific Functional Scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther 1998;27:331–8. 32. Streiner DL. Starting at the beginning: an introduction to coefficient alpha and internal consistency. J Pers Assess 2003;80:99–103. 33. Angst F, Aeschlimann A, Stucki G. Smallest detectable and minimal clinically important differences of rehabilitation intervention with their implications for required sample sizes using WOMAC and SF36 Quality of life measurement instruments in patients with osteoarthritis of the lower extremities. Arthritis Rheum 2001;45: 384–39. 34. Chui K, Hood E, Klima D. Meaningful change in walking speed. Top Geriatr Rehabil 2012;28:97–103.
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DOI: 10.3109/09638288.2014.890673
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Appendix 1 Spanish version of the LEFS scale. Estimad/a sen¯or/a Estamos interesados en saber si tiene alguna dificultad en alguna de las actividades enumeradas abajo como consecuencia de los problemas de su pierna por los cuales usted esta´ solicitando tratamiento. Por favor, responda a cada una de las actividades. En el dı´a de hoy tiene o tendrı´a alguna dificultad al realizar alguna de las siguientes actividades:
Actividades
Mucha dificultad
Dificultad moderada
Un poco de dificultad
Ninguna dificultad
0 0
1 1
2 2
3
4 4
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2
3 3 3 3
4 4 4 4
0 0
1 1
2 2
3 3
4 4
0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1
2 2 2 2 2 2 2 2 2 2 2
3 3 3 3 3 3 3 3 3 3 3
4 4 4 4 4 4 4 4 4 4 4
1
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Alguna parte de su trabajo habitual, labores dome´sticas o actividades escolares. 2 Suspasatiempos habituales, actividades recreativas y/o deportivas. 3 Al entrar o salir de la ban˜era. 4 Caminando de una habitacio´n a otra 5 Ponie´ndose medias o zapatos. 6 Ponie´ndose en cuclillas. 7 Levantando un objeto por ejemplo una bolsa del supermercado del suelo. 8 Realizando actividades ligeras en su casa. 9 Realizando actividades pesadas en su casa. 10 Subie´ndose o baja´ndose de un coche. 11 Caminando 250 metros. 12 Caminando un kilo´metro. 13 Subiendo o bajando 10 peldan˜os de una escalera. 14 Estando de pie durante una hora. 15 Estando sentado durante una hora. 16 Corriendo sobre terreno peano. 17 Corriendo sobre terreno irregular. 18 Haciendo giros bruscos mientras corre ra´pidamente. 19 Saltando. 20 Al darse la vuelta en la cama. Total columna:
Dificultad extrema o incapaz de realizar la actividad
Puntuacio´n__/80
