Disability and Rehabilitation
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Cross-cultural adaptation, reliability and validity of the Arabic version of the reduced Western Ontario and McMaster Universities Osteoarthritis index in patients with knee osteoarthritis Ahmad Alghadir, Shahnawaz Anwer, Zaheen Ahmed Iqbal & Hisham Abdulaziz Alsanawi To cite this article: Ahmad Alghadir, Shahnawaz Anwer, Zaheen Ahmed Iqbal & Hisham Abdulaziz Alsanawi (2015): Cross-cultural adaptation, reliability and validity of the Arabic version of the reduced Western Ontario and McMaster Universities Osteoarthritis index in patients with knee osteoarthritis, Disability and Rehabilitation To link to this article: http://dx.doi.org/10.3109/09638288.2015.1055380
Published online: 11 Jun 2015.
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RESEARCH PAPER
Cross-cultural adaptation, reliability and validity of the Arabic version of the reduced Western Ontario and McMaster Universities Osteoarthritis index in patients with knee osteoarthritis Ahmad Alghadir1, Shahnawaz Anwer1,2, Zaheen Ahmed Iqbal1, and Hisham Abdulaziz Alsanawi3 Downloaded by [York University Libraries] at 02:40 06 November 2015
1
Rehabilitation Research Chair, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia, 2Padmashree Dr. D. Y. Patil College of Physiotherapy, Dr. D. Y. Patil Vidyapeeth, Pune, India, and 3Department of Orthopaedics, College of Medicine, King Saud University, Riyadh, Saudi Arabia Abstract
Keywords
Purpose: We adapted the reduced Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index for the Arabic language and tested its metric properties in patients with knee osteoarthritis (OA). Methods: One hundred and twenty-one consecutive patients who were referred for physiotherapy to the outpatient department were asked to answer the Arabic version of the reduced WOMAC index (ArWOMAC). After the completion of the ArWOMAC, the intensity of knee pain and general health status were assessed using the visual analog scale (VAS) and the 12-item short form health survey (SF-12), respectively. A second assessment was performed at least 48 h after the first session to assess test–retest reliability. The test–retest reliability was quantified using the intra-class correlation coefficient (ICC), and Cronbach’s alpha was calculated to assess the internal consistency of the Arabic questionnaire. The construct validity was assessed using Spearman rank correlation coefficients. Results: The total ArWOMAC scale and pain and function subscales were internally consistent with Cronbach’s coefficient alpha of 0.91, 0.89 and 0.90, respectively. Test–retest reliability was good to excellent with ICC of 0.91, 0.89 and 0.90, respectively. SF-12 and VAS score significantly correlated with ArWOMAC index (p50.01), which support the construct validity. The standard error of measurement (SEM) of the total scale was 2.94, based on repeated measurements for test–retest. The minimum detectable change based on the SEM for test–retest was 8.15. Conclusions: The ArWOMAC index is a reliable and valid instrument for evaluating the severity of knee OA, with metric properties in agreement with the original version.
Arabic, knee, osteoarthritis, reduced WOMAC index, reliability, validity History Received 24 September 2014 Revised 14 May 2015 Accepted 22 May 2015 Published online 11 June 2015
ä Implications for Rehabilitation
Although, the reduced WOMAC index has been clinically utilized within the Saudi population, the Arabic version of this instrument is not validated for an Arab population to measure lower limb functional disability caused by OA. The Arabic version of reduced WOMAC (ArWOMAC) index is a reliable and valid scale to measure lower limb functional disability in patients with knee OA. The ArWOMAC index could be suitable in Saudi Arabia and other Arab countries where the language, culture and the life style are similar.
Introduction Osteoarthritis (OA) of the knee is the major cause of musculoskeletal disability in older men and women [1–3]. According to the World Health Organization report on the global burden of disease, knee OA is likely to become the fourth most common cause of disability in women and the eighth most common cause in men [4]. Knee OA causes pain, joint stiffness and decreased
Address for correspondence: Shahnawaz Anwer, MPT, Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia. Tel: +966 595668288. E-mail: [email protected]
quadriceps strength resulting in physical disability and disease progression [5–8]. Assessment of functional status by self-reported questionnaires and scales has been an important task for clinicians and researchers. A large number of disease-specific assessment scales have been developed over time to assess patients’ functional status. However, the standardization of these clinical tests has always been a matter of concern. In order to allow uniformity and standardization of functional status assessments for patients with knee OA, the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index [9,10] was developed. The reliability and validity of the WOMAC index have been established, and this index has been used in diverse clinical and
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interventional environments [9,10]. The WOMAC index is among the most widely used assessments in arthritis research. Several studies have shown redundancy within the WOMAC index function scale and have suggested that the scale should be developed further, omitting redundant items [11,12]. Reliability studies have also shown that the scale has values of Cronbach’s alpha of greater than 0.9, which indicates that there is the opportunity for trimming [13]. Hence, a reduced version of the WOMAC index has been developed and has been found to be a reliable, valid and responsive measure of outcomes compared to the full version WOMAC index [10]. The full version WOMAC index has been translated into several languages, and validated translations are strongly encouraged worldwide. Guermazi et al. [14] tested the reliability and validity of an adaptation version of the WOMAC index translated into Arabic for Tunisian people. The translated scale was reliable but not valid in its original form. They suggested using the Sfax modified WOMAC in which eight items of physical function subscales (items 1, 2, 7, 12, 13, 15, 16 and 17) from the original English WOMAC index were removed. Faik et al. [15] have translated the WOMAC index into Moroccan Arabic and tested the validity and reliability of the adapted version in a Moroccan population with knee OA. The Moroccan version of the WOMAC index is a reliable and valid instrument in individuals with knee OA. As per literature review, no study has investigated the reliability and validity of an adaptation of the original WOMAC index into Saudi Arabic. Furthermore, no study to date has evaluated the validity and reliability of the reduced WOMAC index into any other language including Arabic. Many patients in Saudi Arabia have difficulty in reading and writing in English and hence, there is a great need to translate the reduced WOMAC index into a local Arabic language. Hence, this study aimed to provide cross-cultural adaptation and establish the reliability and validity of the Arabic translation of the reduced WOMAC index.
Materials and methods Participants and criteria This study used a convenience sample of patients already diagnosed with OA as per the American College of Rheumatology (ACR) who were referred for physiotherapy to the outpatient department of King Khaled University Hospital, Riyadh, Saudi Arabia. OA severity was assessed according to the Kellgren and Lawrence scale [16]. Both male and female patients in the age range of 40–80 years who were able to read and understand Arabic were included. Subjects were excluded if they had any knee, hip or back deformities; any central or peripheral nervous system involvement; were uncooperative patients or were unable to read and understand Arabic. One hundred and sixty participants were screened, and 140 were found eligible. Ethical approval was obtained from the Rehabilitation Research Chair, King Saud University, Riyadh, Saudi Arabia, and every patient who participated in the study provided written informed consent. Procedures Participants were briefed about the procedure before responding to the scale. The participants’ age, sex, height, weight, body mass index (BMI) and OA grade were recorded from the interview and medical records. The study was carried out in two phases. First, the reduced WOMAC index was translated into Arabic and adapted using the Beaton and Guillemin criteria [17,18], and pilot testing of the Arabic version was carried out. Second, a thorough analysis of the measurement properties of the questionnaire was performed.
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Translation and cross-cultural adaptation Two independent bilingual translators, whose first language was Arabic, translated the English version of the reduced WOMAC index into Arabic. One translator had a medical background and an understanding of the purpose and utilization of the WOMAC index while the other was a professional translator without a medical background and had no previous exposure to the WOMAC index. Both translators created a separate Arabic forward translation, and the two translators examined both versions, discussed inconsistencies and reached a consensus on their differences in the translations. Following this process, they agreed upon a synthesized version of the Arabic reduced WOMAC (ArWOMAC) index. Two independent translators then translated the synthesized version of the forward translation back into English using the same process. The crossculturally adapted Arabic version was pilot tested on 30 patients. These patients were later included in the final analysis. The patients were asked to sit comfortably and mark the appropriate point on the scoring system of the Arabic questionnaire that represented their status of knee pain and disability. They were asked about any difficulties that they had in understanding the ArWOMAC index. An expert review committee, including a rheumatologist, discussed all information from the translators and participants. The validity and reliability of the final version were tested in an Arabic-speaking Saudi population with knee OA (Table 1) [17,18]. Psychometric testing Test–retest reliability of the ArWOMAC index was examined by having each patient complete the questionnaire twice, with the second session at least 48 h after the first session to minimize the effect of changes in the patient’s clinical condition. One author was involved in data collection at both sessions. The reduced WOMAC index was designed to measure pain and physical function associated with OA of the lower limbs by assessing five pain-related activities and seven functional activities. The scores for the subscale on pain and physical function subscales were calculated separately. The score for pain was 0–20 and the score for physical function subscales was 0–28. A total score, which was the sum of both subscales, was 0–48. Higher scores indicated greater disability [10]. The construct validity of the ArWOMAC index was examined by testing the assumption that if it was a valid measure of knee disability, its scores should correlate to the intensity of knee pain and health status measured using the visual analog scale (VAS) and the 12-item short form health survey (SF-12), respectively. Table 1. Original version of reduced WOMAC and back-translation of the Arabic version into English. Original reduced WOMAC index
Back-translation (ArWOMAC)
Pain Walking on flat surface Stair climbing Nocturnal Rest Weight bearing Function Ascending (going up) stairs Rising from sitting Walking on a flat surface Getting in or out of car Putting on socks Rising from bed Sitting
Pain Walking on even surface Ascending stairs During night Rest Bearing weight on feet Function Ascending (climbing) stairs Getting up from sitting Walking on even surface Entering the car or getting out of it Donning socks Getting up from bed Sitting
Arabic version of reduced WOMAC index
DOI: 10.3109/09638288.2015.1055380
The VAS is a 10-cm scale ranging from 0 (no pain) to 10 (extreme pain). It is a reliable and valid instrument for assessing acute and chronic pain [19,20]. The SF-12 contains 12 items from the original SF-36 designed to assess general, physical and psychological symptoms and activity limitations due to physical and mental health in the last 4 weeks [21]. The SF-12 contains 12 items from the original SF-36. Ware et al. developed item weights for the SF-12 using an orthogonal factor rotation method to provide physical (PCS-12) and mental component summary (MCS-12) scales [21].
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Statistical analysis Data were analyzed using SPSS for Windows version 19 (Statistical package for Social Sciences, IBM Inc., Chicago, IL). The normality of the data was assessed using the Shapiro–Wilk test. The results of the Shapiro–Wilk test indicated that the data were not normally distributed (p50.05). Therefore, a nonparametric test was used to analyze the data. The test–retest reliability of the ArWOMAC full scale and pain and function subscales was assessed using intraclass correlation coefficients (ICC). The Cronbach’s alpha value was also determined. Reliability testing was done individually for the pain scale, function scale and ArWOMAC full scale at a 95% confidence interval. Systematic differences between the two assessments were performed using a paired t-test, and differences were plotted against the average of the two assessments using a Bland–Altman plot, with a 95% confidence interval (CI) and 95% limit of agreement (LOA). The absolute measurement of error was estimated by calculating the standard error of measurement (SEM), which was used to calculate the minimal detectable change (MDC) (MDC ¼ 1.96 ˇ2 SEM) [22–24]. The construct validity was assessed using Spearman rank correlation coefficients. Spearman rank coefficient values were interpreted as follows: excellent relationship,40.91; good, 0.90–0.71; moderate, 0.70–0.51; fair, 0.50–0.31 and little or none,50.30 [25]. Nineteen participants did not complete the second assessment and were excluded from the final analysis. Data analysis was performed for 121 participants for all three scores. The level of significance in all tests was p50.05.
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Table 2. Participants’ characteristics. Gender, % Male Female Age, years Mean (SD) Range Height, m Mean (SD) Range Weight, kg Mean (SD) Range BMI, kg/m2 Mean (SD) Range K/L rating score, no. (%) Grade 1 Grade 2 Grade 3 Grade 4
46.3 53.7 52.94 (9.28) 40–80 1.69 (0.06) 1.49–1.86 86.43 (13.91) 56–123 30.06 (4.20) 21.38–41.43 19 (15.7) 55 (45.5) 36 (29.8) 11 (9.1)
Table 3. Descriptive statistics of baseline scores. VAS (0–10 cm) Mean (SD) Range SF12-PCS Mean (SD) Range SF12-MCS Mean (SD) Range ArWOMAC, total scale Mean (SD) Range ArWOMAC, pain scale Mean (SD) Range ArWOMAC, function scale Mean (SD) Range
5.85 (2.32) 1–10 38.31 (10.78) 18.6–57 43.92 (10.81) 23.6–62.9 21.46 (9.93) 3–43 8.98 (4.14) 1–16 12.46 (5.98) 1–27
Table 4. Reliability of Arabic language reduced WOMAC (ArWOMAC).
Results Table 2 details the participants’ characteristics. The mean ages of the male and female participants were 53.18 ± 9.24 years and 52.74 ± 9.38 years, respectively. The mean BMI was 29.90 ± 3.96 and 30.09 ± 4.42 kg/m2 in male and female participants, respectively. The sample consisted of 65 female and 56 male participants with varying grades of knee OA. The majority of the male participants (53.6%) had grade 2 OA followed by 23.2% of the participants who had grade 3 OA, whereas 38.5% of the female participants had grade 2 OA followed by 35.4% of the participants who had grade 3 OA, as per the Kellgren and Lawrence rating score [16]. Table 3 details the baseline score of the VAS, SF12-PCS, SF 12-MCS, ArWOMAC pain scale, function scale and total scale. Reliability The Cronbach’s alpha values for the pain scale (0.893), function scale (0.907) and total scale (0.905) of ArWOMAC were all high. Similarly, the ICC for the pain, function and total scales of the ArWOMAC were all high (Table 4). The Bland–Altman limits of agreement between the test and retest scores of the total scale of the questionnaires are depicted in Figure 1. No statistically significant mean differences in scores were found between the first and second administrations of the ArWOMAC with mean differences of 0.89 (95% CI 1.86 to 0.08). The upper and
ICC (95% CI)
da
WOMAC Pain 0.89 (0.84–0.92) 0.05 Function 0.90 (0.86–0.93) 0.86 Total 0.91 (0.87–0.93) 0.89
a
SDdiff
SEMb (95% CI)
MDC
2.53 3.32 5.42
1.37 (2.79 to 2.69) 1.89 (4.64 to 2.92) 2.94 (6.77 to 4.99)
3.80 5.24 8.15
ICC, intraclass correlation coefficients; d, mean difference; SDdiff, standard deviation of the differences; SEM, standard error of measurement; CI, confidence interval; MDC, minimal detectable change. a Differences are for each subject between test and retest. b To compute the SEM, the SD of the first trial (Table 3) was used.
lower LOA were 9.73 and 11.51, respectively. The SEM was 2.94, based on repeated measurements for test–retest. The MDC based on the SEM for test–retest was 8.15 (Table 4). Validity Face validity was established in the original English version of the reduced WOMAC index and was considered adequate for the ArWOMAC after discussions within the expert committee (Stage 4); i.e. the content of the translated items was understandable, pertinent to knee-related activities of daily living and could be used in the assessment of knee pain and function [26,27].
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Figure 1. Bland–Altman plot: intra-individual differences (n ¼ 121) between the Arabic reduced WOMAC on test and retest, plotted against the average of the two scores. The central line represents the mean difference and the dashed lines display the 95% LOA.
Table 5. Construct validity of the ArWOMAC index in knee OA patients.
ArWOMAC Pain Function Total
VAS
SF-12 PCS
SF-12 MCS
0.81 0.77 0.80
0.83 0.82 0.84
0.73 0.71 0.73
MCS, mental component summary score; PCS, physical component summary score; VAS, visual analog scale. All correlations were significant at p50.01 (Spearman rank coefficients).
Construct validity was assessed using Spearman rank coefficients between the initial total ArWOMAC scale, individual pain scale, individual function scale and the baseline scores of the VAS, SF12-PCS and SF 12-MCS. There was a good positive correlation between the VAS score and the ArWOMAC pain scale, the VAS score and the function scale, and the VAS score and the total ArWOMAC scale. There was a good negative correlation between the SF 12-PCS score and the ArWOMAC pain scale, the SF 12-PCS score and the function scale, and the SF 12-PCS score and the total ArWOMAC scale. Similarly, there was a good negative correlation between the SF 12-MCS score and the ArWOMAC pain scale, the SF 12-MCS score and the function scale, and the SF 12-MCS score and the total ArWOMAC scale (Table 5).
Discussion As per literature review, previous studies have investigated the reliability and validity of both Tunisian Arabic and Moroccan Arabic translations and adaptations of the original WOMAC index for patients with knee OA but not for a Saudi Arab population [14,15]. In addition, no study to date has evaluated validity and reliability of the reduced WOMAC index in any other language including Arabic. In this study, we presented the process of crosscultural adaptation of the reduced WOMAC index into the Arabic language and provided evidence of its reliability and validity in patients with knee OA. The study was carried out in two phases. First, the reduced WOMAC index was translated and adapted into
Arabic using the Beaton and Guillemin criteria [17,18], then pilot tested. Second, a thorough analysis of the measurement properties of the questionnaire was done. The wording of the ArWOMAC index was simple and used literal Arabic language to enable use in the largest possible Arab population. Although, certain terms used in our study were slightly different from those used in the original scale, the use of the term ‘‘walking on an even surface (our translation) or ‘walking on a flat surface’’’ (original scale) and ‘‘donning socks (our translation) or ‘putting on socks’’’ (original scale) will not substantially change patient responses. Reliability was assessed in terms of internal consistency (Cronbach’s alpha coefficient) and test–retest reliability (ICC analysis). Cronbach’s alpha coefficients were acceptable for both dimensions of the ArWOMAC index according to standards recommended by Streiner and Norman [28]; this indicates that each domain addressed a somewhat different aspect of functional disability. Similar to the original English questionnaire, we found high internal consistency and a significant correlation between the ArWOMAC index, VAS, SF12-PCS and SF12-MCS scores. The total ArWOMAC index had an ICC value of 0.91, which was higher than that of the English WOMAC index (ICC ¼ 0.87) [10]. Similarly, Faik et al. [15] reported an ICC of 0.91 for the total Arabic WOMAC index in a Moroccan population with knee OA. However, Basaran et al. [29] reported a slightly higher ICC value (0.95) for the total WOMAC index in a Turkish population with knee OA. Similarly, Bae et al. [30] reported the total Korean WOMAC index had an ICC of 0.95. The ICC of the ArWOMAC pain and function subscales was 0.89 and 0.90, respectively. The ICC value of the pain and function subscales of the English reduced WOMAC index were not reported. However, the ICC values of the Sfax modified WOMAC, which is an Arabic version of the full WOMAC, were 0.84, 0.84 and 0.92 for pain, stiffness and modified physical function subscales, respectively [14]. The results of a previous study done by Salaffi et al. [31] revealed that the ICC of the Italian version WOMAC index was 0.86, 0.68 and 0.89 for pain, stiffness and physical function, respectively. Similarly, Bae et al. [30] reported that the ICC of the Korean WOMAC index was 0.85, 0.79 and 0.89 for pain, stiffness and physical function, respectively. In addition, Faik et al. [15] reported that the ICC of the Arabic WOMAC index in a Moroccan
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DOI: 10.3109/09638288.2015.1055380
population with knee OA was 0.80, 0.77 and 0.89 for pain, stiffness and physical function, respectively. Construct validity was investigated in terms of convergence between like dimensions of the self-administered WOMAC, VAS and SF-12. A good correlation was noted between the VAS score, ArWOMAC subscales and the total scale. Similarly, a good correlation was noted between the SF-12 PCS and MCS with ArWOMAC subscales and total scale. Bae et al. [30] reported a significant correlation of the KWOMAC with the KLequesne in the total and subscale scores. Salaffi et al. [31] reported significant correlations between the WOMAC index and the SF36 (pain, physical function and MCS). In addition, Faik et al. [15] reported significant correlations between the WOMAC index and the VAS in a Moroccan population with knee OA. Furthermore, Basaran et al. [29] reported moderately good correlations between the WOMAC index and the SF-36 (pain and physical function) and weak-to-moderate correlations between the WOMAC index and the VAS. In addition, the present study calculated the SEM and the MDC of the ArWOMAC index in patients with knee OA. To our knowledge, no study has investigated the SEM and MDC for the original reduced WOMAC index in patients with knee OA. SEM is one of the most appropriate method for estimating the statistically meaningful change of a health outcome measurement [22,23]. The present study had some limitations, including the lack of longitudinal data with respect to other psychometric properties, such as responsiveness or sensitivity to change, and error scores as a representation of a minimally clinically important difference. Further study is recommended to examine the sensitivity to change (responsiveness) and the minimally clinically important (perceptible) difference for the ArWOMAC index, in order to complete the assessment of its psychometric properties. Moreover, factor analysis of individual questions was not performed, as was done in the original study and other related studies. This would further help to substantiate the progress of the study and its positive results. In addition, the Saudi population engages in five prayers times, which include a position of ‘‘bending to the floor’’. The question on this activity was present in the original WOMAC function scale, but it was omitted in the reduced WOMAC functional scale. Therefore, this question could evaluate difficulties in activities such as praying.
Conclusions The results of the present study indicate that the Arabic version of the reduced WOMAC index is a reliable and valid instrument for evaluating the severity of knee OA, with psychometric properties in agreement with the original version. Although, we have not yet studied the sensitivity of the ArWOMAC index to change (i.e. responsiveness), this study has implications for future clinical trials in knee OA.
Declaration of interest The project was full financially supported by King Saud University, through Vice Deanship of Research Chairs, Rehabilitation Research Chair. The authors report no conflicts of interest.
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ISSN: 0963-8288 (Print) 1464-5165 (Online) Journal homepage: http://www.tandfonline.com/loi/idre20
Cross-cultural adaptation, reliability and validity of the Arabic version of the reduced Western Ontario and McMaster Universities Osteoarthritis index in patients with knee osteoarthritis Ahmad Alghadir, Shahnawaz Anwer, Zaheen Ahmed Iqbal & Hisham Abdulaziz Alsanawi To cite this article: Ahmad Alghadir, Shahnawaz Anwer, Zaheen Ahmed Iqbal & Hisham Abdulaziz Alsanawi (2015): Cross-cultural adaptation, reliability and validity of the Arabic version of the reduced Western Ontario and McMaster Universities Osteoarthritis index in patients with knee osteoarthritis, Disability and Rehabilitation To link to this article: http://dx.doi.org/10.3109/09638288.2015.1055380
Published online: 11 Jun 2015.
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RESEARCH PAPER
Cross-cultural adaptation, reliability and validity of the Arabic version of the reduced Western Ontario and McMaster Universities Osteoarthritis index in patients with knee osteoarthritis Ahmad Alghadir1, Shahnawaz Anwer1,2, Zaheen Ahmed Iqbal1, and Hisham Abdulaziz Alsanawi3 Downloaded by [York University Libraries] at 02:40 06 November 2015
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Rehabilitation Research Chair, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia, 2Padmashree Dr. D. Y. Patil College of Physiotherapy, Dr. D. Y. Patil Vidyapeeth, Pune, India, and 3Department of Orthopaedics, College of Medicine, King Saud University, Riyadh, Saudi Arabia Abstract
Keywords
Purpose: We adapted the reduced Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index for the Arabic language and tested its metric properties in patients with knee osteoarthritis (OA). Methods: One hundred and twenty-one consecutive patients who were referred for physiotherapy to the outpatient department were asked to answer the Arabic version of the reduced WOMAC index (ArWOMAC). After the completion of the ArWOMAC, the intensity of knee pain and general health status were assessed using the visual analog scale (VAS) and the 12-item short form health survey (SF-12), respectively. A second assessment was performed at least 48 h after the first session to assess test–retest reliability. The test–retest reliability was quantified using the intra-class correlation coefficient (ICC), and Cronbach’s alpha was calculated to assess the internal consistency of the Arabic questionnaire. The construct validity was assessed using Spearman rank correlation coefficients. Results: The total ArWOMAC scale and pain and function subscales were internally consistent with Cronbach’s coefficient alpha of 0.91, 0.89 and 0.90, respectively. Test–retest reliability was good to excellent with ICC of 0.91, 0.89 and 0.90, respectively. SF-12 and VAS score significantly correlated with ArWOMAC index (p50.01), which support the construct validity. The standard error of measurement (SEM) of the total scale was 2.94, based on repeated measurements for test–retest. The minimum detectable change based on the SEM for test–retest was 8.15. Conclusions: The ArWOMAC index is a reliable and valid instrument for evaluating the severity of knee OA, with metric properties in agreement with the original version.
Arabic, knee, osteoarthritis, reduced WOMAC index, reliability, validity History Received 24 September 2014 Revised 14 May 2015 Accepted 22 May 2015 Published online 11 June 2015
ä Implications for Rehabilitation
Although, the reduced WOMAC index has been clinically utilized within the Saudi population, the Arabic version of this instrument is not validated for an Arab population to measure lower limb functional disability caused by OA. The Arabic version of reduced WOMAC (ArWOMAC) index is a reliable and valid scale to measure lower limb functional disability in patients with knee OA. The ArWOMAC index could be suitable in Saudi Arabia and other Arab countries where the language, culture and the life style are similar.
Introduction Osteoarthritis (OA) of the knee is the major cause of musculoskeletal disability in older men and women [1–3]. According to the World Health Organization report on the global burden of disease, knee OA is likely to become the fourth most common cause of disability in women and the eighth most common cause in men [4]. Knee OA causes pain, joint stiffness and decreased
Address for correspondence: Shahnawaz Anwer, MPT, Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia. Tel: +966 595668288. E-mail: [email protected]
quadriceps strength resulting in physical disability and disease progression [5–8]. Assessment of functional status by self-reported questionnaires and scales has been an important task for clinicians and researchers. A large number of disease-specific assessment scales have been developed over time to assess patients’ functional status. However, the standardization of these clinical tests has always been a matter of concern. In order to allow uniformity and standardization of functional status assessments for patients with knee OA, the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index [9,10] was developed. The reliability and validity of the WOMAC index have been established, and this index has been used in diverse clinical and
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interventional environments [9,10]. The WOMAC index is among the most widely used assessments in arthritis research. Several studies have shown redundancy within the WOMAC index function scale and have suggested that the scale should be developed further, omitting redundant items [11,12]. Reliability studies have also shown that the scale has values of Cronbach’s alpha of greater than 0.9, which indicates that there is the opportunity for trimming [13]. Hence, a reduced version of the WOMAC index has been developed and has been found to be a reliable, valid and responsive measure of outcomes compared to the full version WOMAC index [10]. The full version WOMAC index has been translated into several languages, and validated translations are strongly encouraged worldwide. Guermazi et al. [14] tested the reliability and validity of an adaptation version of the WOMAC index translated into Arabic for Tunisian people. The translated scale was reliable but not valid in its original form. They suggested using the Sfax modified WOMAC in which eight items of physical function subscales (items 1, 2, 7, 12, 13, 15, 16 and 17) from the original English WOMAC index were removed. Faik et al. [15] have translated the WOMAC index into Moroccan Arabic and tested the validity and reliability of the adapted version in a Moroccan population with knee OA. The Moroccan version of the WOMAC index is a reliable and valid instrument in individuals with knee OA. As per literature review, no study has investigated the reliability and validity of an adaptation of the original WOMAC index into Saudi Arabic. Furthermore, no study to date has evaluated the validity and reliability of the reduced WOMAC index into any other language including Arabic. Many patients in Saudi Arabia have difficulty in reading and writing in English and hence, there is a great need to translate the reduced WOMAC index into a local Arabic language. Hence, this study aimed to provide cross-cultural adaptation and establish the reliability and validity of the Arabic translation of the reduced WOMAC index.
Materials and methods Participants and criteria This study used a convenience sample of patients already diagnosed with OA as per the American College of Rheumatology (ACR) who were referred for physiotherapy to the outpatient department of King Khaled University Hospital, Riyadh, Saudi Arabia. OA severity was assessed according to the Kellgren and Lawrence scale [16]. Both male and female patients in the age range of 40–80 years who were able to read and understand Arabic were included. Subjects were excluded if they had any knee, hip or back deformities; any central or peripheral nervous system involvement; were uncooperative patients or were unable to read and understand Arabic. One hundred and sixty participants were screened, and 140 were found eligible. Ethical approval was obtained from the Rehabilitation Research Chair, King Saud University, Riyadh, Saudi Arabia, and every patient who participated in the study provided written informed consent. Procedures Participants were briefed about the procedure before responding to the scale. The participants’ age, sex, height, weight, body mass index (BMI) and OA grade were recorded from the interview and medical records. The study was carried out in two phases. First, the reduced WOMAC index was translated into Arabic and adapted using the Beaton and Guillemin criteria [17,18], and pilot testing of the Arabic version was carried out. Second, a thorough analysis of the measurement properties of the questionnaire was performed.
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Translation and cross-cultural adaptation Two independent bilingual translators, whose first language was Arabic, translated the English version of the reduced WOMAC index into Arabic. One translator had a medical background and an understanding of the purpose and utilization of the WOMAC index while the other was a professional translator without a medical background and had no previous exposure to the WOMAC index. Both translators created a separate Arabic forward translation, and the two translators examined both versions, discussed inconsistencies and reached a consensus on their differences in the translations. Following this process, they agreed upon a synthesized version of the Arabic reduced WOMAC (ArWOMAC) index. Two independent translators then translated the synthesized version of the forward translation back into English using the same process. The crossculturally adapted Arabic version was pilot tested on 30 patients. These patients were later included in the final analysis. The patients were asked to sit comfortably and mark the appropriate point on the scoring system of the Arabic questionnaire that represented their status of knee pain and disability. They were asked about any difficulties that they had in understanding the ArWOMAC index. An expert review committee, including a rheumatologist, discussed all information from the translators and participants. The validity and reliability of the final version were tested in an Arabic-speaking Saudi population with knee OA (Table 1) [17,18]. Psychometric testing Test–retest reliability of the ArWOMAC index was examined by having each patient complete the questionnaire twice, with the second session at least 48 h after the first session to minimize the effect of changes in the patient’s clinical condition. One author was involved in data collection at both sessions. The reduced WOMAC index was designed to measure pain and physical function associated with OA of the lower limbs by assessing five pain-related activities and seven functional activities. The scores for the subscale on pain and physical function subscales were calculated separately. The score for pain was 0–20 and the score for physical function subscales was 0–28. A total score, which was the sum of both subscales, was 0–48. Higher scores indicated greater disability [10]. The construct validity of the ArWOMAC index was examined by testing the assumption that if it was a valid measure of knee disability, its scores should correlate to the intensity of knee pain and health status measured using the visual analog scale (VAS) and the 12-item short form health survey (SF-12), respectively. Table 1. Original version of reduced WOMAC and back-translation of the Arabic version into English. Original reduced WOMAC index
Back-translation (ArWOMAC)
Pain Walking on flat surface Stair climbing Nocturnal Rest Weight bearing Function Ascending (going up) stairs Rising from sitting Walking on a flat surface Getting in or out of car Putting on socks Rising from bed Sitting
Pain Walking on even surface Ascending stairs During night Rest Bearing weight on feet Function Ascending (climbing) stairs Getting up from sitting Walking on even surface Entering the car or getting out of it Donning socks Getting up from bed Sitting
Arabic version of reduced WOMAC index
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The VAS is a 10-cm scale ranging from 0 (no pain) to 10 (extreme pain). It is a reliable and valid instrument for assessing acute and chronic pain [19,20]. The SF-12 contains 12 items from the original SF-36 designed to assess general, physical and psychological symptoms and activity limitations due to physical and mental health in the last 4 weeks [21]. The SF-12 contains 12 items from the original SF-36. Ware et al. developed item weights for the SF-12 using an orthogonal factor rotation method to provide physical (PCS-12) and mental component summary (MCS-12) scales [21].
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Statistical analysis Data were analyzed using SPSS for Windows version 19 (Statistical package for Social Sciences, IBM Inc., Chicago, IL). The normality of the data was assessed using the Shapiro–Wilk test. The results of the Shapiro–Wilk test indicated that the data were not normally distributed (p50.05). Therefore, a nonparametric test was used to analyze the data. The test–retest reliability of the ArWOMAC full scale and pain and function subscales was assessed using intraclass correlation coefficients (ICC). The Cronbach’s alpha value was also determined. Reliability testing was done individually for the pain scale, function scale and ArWOMAC full scale at a 95% confidence interval. Systematic differences between the two assessments were performed using a paired t-test, and differences were plotted against the average of the two assessments using a Bland–Altman plot, with a 95% confidence interval (CI) and 95% limit of agreement (LOA). The absolute measurement of error was estimated by calculating the standard error of measurement (SEM), which was used to calculate the minimal detectable change (MDC) (MDC ¼ 1.96 ˇ2 SEM) [22–24]. The construct validity was assessed using Spearman rank correlation coefficients. Spearman rank coefficient values were interpreted as follows: excellent relationship,40.91; good, 0.90–0.71; moderate, 0.70–0.51; fair, 0.50–0.31 and little or none,50.30 [25]. Nineteen participants did not complete the second assessment and were excluded from the final analysis. Data analysis was performed for 121 participants for all three scores. The level of significance in all tests was p50.05.
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Table 2. Participants’ characteristics. Gender, % Male Female Age, years Mean (SD) Range Height, m Mean (SD) Range Weight, kg Mean (SD) Range BMI, kg/m2 Mean (SD) Range K/L rating score, no. (%) Grade 1 Grade 2 Grade 3 Grade 4
46.3 53.7 52.94 (9.28) 40–80 1.69 (0.06) 1.49–1.86 86.43 (13.91) 56–123 30.06 (4.20) 21.38–41.43 19 (15.7) 55 (45.5) 36 (29.8) 11 (9.1)
Table 3. Descriptive statistics of baseline scores. VAS (0–10 cm) Mean (SD) Range SF12-PCS Mean (SD) Range SF12-MCS Mean (SD) Range ArWOMAC, total scale Mean (SD) Range ArWOMAC, pain scale Mean (SD) Range ArWOMAC, function scale Mean (SD) Range
5.85 (2.32) 1–10 38.31 (10.78) 18.6–57 43.92 (10.81) 23.6–62.9 21.46 (9.93) 3–43 8.98 (4.14) 1–16 12.46 (5.98) 1–27
Table 4. Reliability of Arabic language reduced WOMAC (ArWOMAC).
Results Table 2 details the participants’ characteristics. The mean ages of the male and female participants were 53.18 ± 9.24 years and 52.74 ± 9.38 years, respectively. The mean BMI was 29.90 ± 3.96 and 30.09 ± 4.42 kg/m2 in male and female participants, respectively. The sample consisted of 65 female and 56 male participants with varying grades of knee OA. The majority of the male participants (53.6%) had grade 2 OA followed by 23.2% of the participants who had grade 3 OA, whereas 38.5% of the female participants had grade 2 OA followed by 35.4% of the participants who had grade 3 OA, as per the Kellgren and Lawrence rating score [16]. Table 3 details the baseline score of the VAS, SF12-PCS, SF 12-MCS, ArWOMAC pain scale, function scale and total scale. Reliability The Cronbach’s alpha values for the pain scale (0.893), function scale (0.907) and total scale (0.905) of ArWOMAC were all high. Similarly, the ICC for the pain, function and total scales of the ArWOMAC were all high (Table 4). The Bland–Altman limits of agreement between the test and retest scores of the total scale of the questionnaires are depicted in Figure 1. No statistically significant mean differences in scores were found between the first and second administrations of the ArWOMAC with mean differences of 0.89 (95% CI 1.86 to 0.08). The upper and
ICC (95% CI)
da
WOMAC Pain 0.89 (0.84–0.92) 0.05 Function 0.90 (0.86–0.93) 0.86 Total 0.91 (0.87–0.93) 0.89
a
SDdiff
SEMb (95% CI)
MDC
2.53 3.32 5.42
1.37 (2.79 to 2.69) 1.89 (4.64 to 2.92) 2.94 (6.77 to 4.99)
3.80 5.24 8.15
ICC, intraclass correlation coefficients; d, mean difference; SDdiff, standard deviation of the differences; SEM, standard error of measurement; CI, confidence interval; MDC, minimal detectable change. a Differences are for each subject between test and retest. b To compute the SEM, the SD of the first trial (Table 3) was used.
lower LOA were 9.73 and 11.51, respectively. The SEM was 2.94, based on repeated measurements for test–retest. The MDC based on the SEM for test–retest was 8.15 (Table 4). Validity Face validity was established in the original English version of the reduced WOMAC index and was considered adequate for the ArWOMAC after discussions within the expert committee (Stage 4); i.e. the content of the translated items was understandable, pertinent to knee-related activities of daily living and could be used in the assessment of knee pain and function [26,27].
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Figure 1. Bland–Altman plot: intra-individual differences (n ¼ 121) between the Arabic reduced WOMAC on test and retest, plotted against the average of the two scores. The central line represents the mean difference and the dashed lines display the 95% LOA.
Table 5. Construct validity of the ArWOMAC index in knee OA patients.
ArWOMAC Pain Function Total
VAS
SF-12 PCS
SF-12 MCS
0.81 0.77 0.80
0.83 0.82 0.84
0.73 0.71 0.73
MCS, mental component summary score; PCS, physical component summary score; VAS, visual analog scale. All correlations were significant at p50.01 (Spearman rank coefficients).
Construct validity was assessed using Spearman rank coefficients between the initial total ArWOMAC scale, individual pain scale, individual function scale and the baseline scores of the VAS, SF12-PCS and SF 12-MCS. There was a good positive correlation between the VAS score and the ArWOMAC pain scale, the VAS score and the function scale, and the VAS score and the total ArWOMAC scale. There was a good negative correlation between the SF 12-PCS score and the ArWOMAC pain scale, the SF 12-PCS score and the function scale, and the SF 12-PCS score and the total ArWOMAC scale. Similarly, there was a good negative correlation between the SF 12-MCS score and the ArWOMAC pain scale, the SF 12-MCS score and the function scale, and the SF 12-MCS score and the total ArWOMAC scale (Table 5).
Discussion As per literature review, previous studies have investigated the reliability and validity of both Tunisian Arabic and Moroccan Arabic translations and adaptations of the original WOMAC index for patients with knee OA but not for a Saudi Arab population [14,15]. In addition, no study to date has evaluated validity and reliability of the reduced WOMAC index in any other language including Arabic. In this study, we presented the process of crosscultural adaptation of the reduced WOMAC index into the Arabic language and provided evidence of its reliability and validity in patients with knee OA. The study was carried out in two phases. First, the reduced WOMAC index was translated and adapted into
Arabic using the Beaton and Guillemin criteria [17,18], then pilot tested. Second, a thorough analysis of the measurement properties of the questionnaire was done. The wording of the ArWOMAC index was simple and used literal Arabic language to enable use in the largest possible Arab population. Although, certain terms used in our study were slightly different from those used in the original scale, the use of the term ‘‘walking on an even surface (our translation) or ‘walking on a flat surface’’’ (original scale) and ‘‘donning socks (our translation) or ‘putting on socks’’’ (original scale) will not substantially change patient responses. Reliability was assessed in terms of internal consistency (Cronbach’s alpha coefficient) and test–retest reliability (ICC analysis). Cronbach’s alpha coefficients were acceptable for both dimensions of the ArWOMAC index according to standards recommended by Streiner and Norman [28]; this indicates that each domain addressed a somewhat different aspect of functional disability. Similar to the original English questionnaire, we found high internal consistency and a significant correlation between the ArWOMAC index, VAS, SF12-PCS and SF12-MCS scores. The total ArWOMAC index had an ICC value of 0.91, which was higher than that of the English WOMAC index (ICC ¼ 0.87) [10]. Similarly, Faik et al. [15] reported an ICC of 0.91 for the total Arabic WOMAC index in a Moroccan population with knee OA. However, Basaran et al. [29] reported a slightly higher ICC value (0.95) for the total WOMAC index in a Turkish population with knee OA. Similarly, Bae et al. [30] reported the total Korean WOMAC index had an ICC of 0.95. The ICC of the ArWOMAC pain and function subscales was 0.89 and 0.90, respectively. The ICC value of the pain and function subscales of the English reduced WOMAC index were not reported. However, the ICC values of the Sfax modified WOMAC, which is an Arabic version of the full WOMAC, were 0.84, 0.84 and 0.92 for pain, stiffness and modified physical function subscales, respectively [14]. The results of a previous study done by Salaffi et al. [31] revealed that the ICC of the Italian version WOMAC index was 0.86, 0.68 and 0.89 for pain, stiffness and physical function, respectively. Similarly, Bae et al. [30] reported that the ICC of the Korean WOMAC index was 0.85, 0.79 and 0.89 for pain, stiffness and physical function, respectively. In addition, Faik et al. [15] reported that the ICC of the Arabic WOMAC index in a Moroccan
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DOI: 10.3109/09638288.2015.1055380
population with knee OA was 0.80, 0.77 and 0.89 for pain, stiffness and physical function, respectively. Construct validity was investigated in terms of convergence between like dimensions of the self-administered WOMAC, VAS and SF-12. A good correlation was noted between the VAS score, ArWOMAC subscales and the total scale. Similarly, a good correlation was noted between the SF-12 PCS and MCS with ArWOMAC subscales and total scale. Bae et al. [30] reported a significant correlation of the KWOMAC with the KLequesne in the total and subscale scores. Salaffi et al. [31] reported significant correlations between the WOMAC index and the SF36 (pain, physical function and MCS). In addition, Faik et al. [15] reported significant correlations between the WOMAC index and the VAS in a Moroccan population with knee OA. Furthermore, Basaran et al. [29] reported moderately good correlations between the WOMAC index and the SF-36 (pain and physical function) and weak-to-moderate correlations between the WOMAC index and the VAS. In addition, the present study calculated the SEM and the MDC of the ArWOMAC index in patients with knee OA. To our knowledge, no study has investigated the SEM and MDC for the original reduced WOMAC index in patients with knee OA. SEM is one of the most appropriate method for estimating the statistically meaningful change of a health outcome measurement [22,23]. The present study had some limitations, including the lack of longitudinal data with respect to other psychometric properties, such as responsiveness or sensitivity to change, and error scores as a representation of a minimally clinically important difference. Further study is recommended to examine the sensitivity to change (responsiveness) and the minimally clinically important (perceptible) difference for the ArWOMAC index, in order to complete the assessment of its psychometric properties. Moreover, factor analysis of individual questions was not performed, as was done in the original study and other related studies. This would further help to substantiate the progress of the study and its positive results. In addition, the Saudi population engages in five prayers times, which include a position of ‘‘bending to the floor’’. The question on this activity was present in the original WOMAC function scale, but it was omitted in the reduced WOMAC functional scale. Therefore, this question could evaluate difficulties in activities such as praying.
Conclusions The results of the present study indicate that the Arabic version of the reduced WOMAC index is a reliable and valid instrument for evaluating the severity of knee OA, with psychometric properties in agreement with the original version. Although, we have not yet studied the sensitivity of the ArWOMAC index to change (i.e. responsiveness), this study has implications for future clinical trials in knee OA.
Declaration of interest The project was full financially supported by King Saud University, through Vice Deanship of Research Chairs, Rehabilitation Research Chair. The authors report no conflicts of interest.
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