Abstract
Objective. To adapt and validate the Malay version of Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) questionnaire. Design. The OAKHQOL was adapted into Malay version using forward-backward translation methodology. It was then validated in a cross-sectional study of 191 patients with knee osteoarthritis (OA). Patients completed the OAKHQOL and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire. Confirmatory analysis, reliability analysis, and Pearson correlation test were performed. Results. The new five-factor model of 28 items demonstrated an acceptable level of goodness of fit (comparative fit index = 0.915, Tucker-Lewis index = 0.905, incremental fit index = 0.916, chi-squared/degree of freedom = 1.953, and root mean square error of approximation = 0.071), signifying a fit model. The Cronbach’s alpha value and the composite reliability of each construct ranged from 0.865 to 0.933 and 0.819 to 0.921, respectively. The Pearson correlation coefficient between the OAKHQOL and the WOMAC showed adequate criterion validity. Known groups validity showed statistical difference in body mass index in physical activity, mental health, and pain construct. The pain domain was statistically different between the age groups. Conclusion. The Malay version OAKHQOL questionnaire is a valid and reliable instrument to assess health-related quality of life in knee OA patients.
1. Introduction
Osteoarthritis (OA) is the most common disease of joints in adults around the world [1, 2]. Due to its chronicity in nature, it is the major cause of pain and disability. OA may affect not only physical functioning, but also mental health (anxiety and depression), sleep, work ability, interpersonal interactions, self-esteem, quality of life, sexuality, and participation [3, 4].
There are few validated instruments used in studies to assess health-related QOL in patients with OA specifically. The Medical Outcomes Study Short-Form 36 (SF36), which has been widely applied to assess QOL, is not disease-specific to OA and was found to have low response rate in population more than 65 years of age [5]. The Lequesne index and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire, which are more disease-specific, are able to measure only pain and function but not the other domains of QOL such as mental, social, and sexual domains [6, 7]. It was suggested that the SF-36 and WOMAC should be used in combination [8]; however, they may still fail to capture specific QOL aspects related to hip or knee osteoarthritis. Knee Injury and Osteoarthritis Outcome Score (KOOS) is another questionnaire but its assessment is not limited to quality of life because it includes pain, other symptoms, activity of daily living, sports, and recreational activity measurements [9]. Thus, the Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) scale questionnaire was developed and validated to measure the impact of specifically knee and hip osteoarthritis on the patient’s QOL.
The OAKHQOL is a specific tool to measure QOL in knee and hip OA as it takes into account specific themes that are exclusive to the QOL of patients with knee and hip OA (social support, sleep, side effects of drugs, plans for the future, embarrassment to be seen by people, use of public transport, difficulty in moving after staying in the same position, and sexuality) [10]. It has 43 items which fall into five domains: physical activity, pain, mental health, social functioning, and social support. Evaluation of the OAKHQOL has shown the reliability of the five domains to be satisfactory (interclass correlation coefficients: 0.70–0.85), the construct validity to be adequate (Spearman correlation coefficients: 0.43–0.75), and the discrimination to be satisfactory [10].
Confirmatory factor analysis (CFA) is a theory-testing model as opposed to exploratory factor analysis (EFA) which is a theory-generating method [11]. CFA is a type of structural equation modeling (SEM) that specifically deals with measurement models, that is, the relationships between observed measures or indicators and latent variables or factors [12, 13]. It is powerful because it provides explicit hypothesis testing for factor analytic problems.
Assessing the QOL among knee OA patients is important to ensure holistic care for the patient. Despite this, the reliability and validity of the OAKHQOL in the Malaysian context have not been established. The need for a validated questionnaire suitable to the local population based on the language is very important as it is more accurate to illustrate the real impact of the disease on the patient’s QOL. Hence, this study aimed to determine the psychometric properties of the Malay version of the OAKHQOL among knee OA patients.
2. Materials and Methods
A cross-sectional study was conducted among 191 patients diagnosed with knee OA between February and August 2014 at the Outpatient Clinic, Universiti Sains Malaysia Hospital, a tertiary teaching hospital in Malaysia. A total of 210 patients were invited, and only 191 patients fulfilled the inclusion and exclusion criteria and were recruited in the study, which give the response rate of 90%. Patients with unilateral or bilateral knee osteoarthritis diagnosed according to the clinical and radiological criteria of the American College of Rheumatology (knee pain and radiographic osteophytes plus at least one of three symptoms/signs), aged more than 50 years, who experienced morning stiffness of less than 30 minutes and crepitus on active motion, and who were able to read in the Malay language were included.
Convenience sampling was applied, and written informed consent was taken. Patients were asked to fill out the Malay version OAKHQOL (Table 7) and the validated Malay Version WOMAC. Sociodemographic data (age, gender, education, and race) and knee OA history were taken. Body mass index (BMI) measurements and weight-bearing anterior-posterior view X-rays of both knees were taken. The participants took about 15 minutes to complete both questionnaires. They also did not have to pay for their participation in the study.
Sample size was determined based on Hair et al. (2010). The minimum sample size required for five or less constructs was 100 samples [14].
2.1. OAKHQOL Questionnaire
This questionnaire was developed by Rat et al. to assess quality of life in knee and hip OA patients [10, 15], specifically to assess health-related quality of life (HRQOL) [10]. The concept of this questionnaire was based on the World Health Organization (WHO) definition of QOL. This is a self-administered questionnaire. The original questionnaire was developed in French and later in English [15]. It was shown to capture patients’ perceptions of their disease, and it possesses the necessary psychometric properties of validity and reliability for use in clinical trials and observational studies [10, 15].
In the original validation study, four factors were identified in the exploratory factor analysis based on scree plot and Eigen values. These factors were physical activities (19 items), mental health (14 items), social support (four items), and social functioning (three items). The pain factor (four items) was found to have loaded on the physical and mental health factors. However, based on expert opinions, the pain factor was included as an individual dimension. Therefore, the final English version of OAKHQOL consists of 43 items divided into five dimensions: physical activity, mental health, pain, social support, and social functioning as well as three additional items [10]. The three additional items are relationship, sexual activity, and professional life. The five dimensions (40 items) (Table 8) and three additional items are intended to be used separately. The three additional items are independent items and were not included in the analysis. Each item in the five dimensions is measured on a numerical rating scale from 0 to 10. The final scores were the mean of scores of all the items in respective domains that ranged between 0 to 10 [10].
2.2. Adaptation of the OAKHQOL Questionnaire
Forward and backward translation was carried out by a group of panelists consisting of family medicine specialists, physicians, linguists, and bilingual laymen. Modifications were made, and content validity was checked. The revised version was tested on 20 patients for face validity. These patients were excluded from the psychometric analysis.
2.3. WOMAC
WOMAC is a disease-specific, self-administered health status measure that is widely used to assess the symptoms and physical disability for people with hip and/or knee OA [16, 17]. It is widely used in OA research especially to evaluate clinical outcome measures as a result of treatment intervention [18]. The WOMAC measures total pain score, total stiffness score, and total physical functioning score. The original index consists of 24 questions (five questions for pain, two questions for stiffness, and 17 questions for physical function). It has been validated in Bahasa, Malaysia [16]. This questionnaire is available in a Likert version rated on an ordinal scale of 0 to 4 and also as a visual analog scale (VAS) [16]. In this study, a VAS version was used.
2.4. Statistical Analysis
Confirmatory factor analysis (CFA), reliability analysis, and Pearson correlation test were performed to assess the psychometric properties using SPSS version 22.0 and Analysis of Moment Structure (AMOS) software version 21.0. On preliminary data screening, cases with incomplete response were removed from data. Further assessment of normality and outliers was performed on the factor scores based on the critical ratio (i.e., for skewness and kurtosis to their standard error) and the Mahalanobis distance. Mahalanobis distance was used to identify the outliers by using AMOS software. It computes and tabulates the distance of every data from the center of all data distribution [19].
The CFA was performed to examine the goodness of fit indices of the Malay OAKHQOL latent construct. Construct validity examines the degree to which a scale measures what it intends to measure [20]. Construct validity is achieved if the goodness of fit indices signify a model fit [20].
The measurement of the model fit was checked with several goodness of fit indicators: comparative fit index (CFI), Tucker-Lewis index (TLI), incremental fit index (IFI), chi-squared/degree of freedom, and root mean square error of approximation (RMSEA) [12, 13, 21]. For approximate fit index, a value of more than 0.9 was taken for CFI, IFI, and TLI [21, 22]. Chi-squared/degree of freedom of less than 3 and RMSEA value of less than 0.08 were taken as indicators of an acceptable level [12, 13, 19].
In addition to the overall evaluation of goodness of fit, the standardized factor loading (standardized regression weight) modification indices (MI) and squared multiple correlation () were used as indicators to select which items should be removed in the model [12, 13]. MI suggested correlations between variables. A high MI value indicates redundancy in a pair of variables [12, 13]. Discriminant validity is also assessed by obtaining correlation values between the constructs. A correlation of more than 0.85 between constructs is considered to indicate poor discriminant validity [12, 13].
Reliability analysis was measured using Cronbach’s alpha coefficient, composite reliability (CR), and average variance extracted (AVE). Reliability refers to the accuracy and precision of the measurement procedure. Cronbach’s alpha coefficient was measured using SPSS. Both CR and AVE were derived from CFA analysis and manually calculated based on published formula [19, 23]. A Cronbach’s alpha coefficient value of more than 0.7 and a CR equal to or greater than 0.6 represent a measure of satisfactory internal consistency [19, 24, 25]. AVE is the average percentage of variation explained by the variables in the construct or domain. The acceptable value for it was taken as more than 0.5 [19]. In this study, the test-retest reliability was not done due to time constraint and limited budget.
The Pearson correlation test was performed to assess the criterion validity of the OAKHQOL. The test was done between the pain construct of the OAKHQOL and the pain construct of the WOMAC, as well as between the physical construct of the OAKHQOL and the functional construct of the WOMAC. The correlation coefficient of more than 0.5 but less than 0.8 was considered to be a good correlation [26].
Known group validity is a method to support construct validity of a questionnaire. The method will evaluate the questionnaire ability to discriminate between the two groups known to differ on the variable of interest [27]. In this study, known group validity was assessed through gender, BMI, age groups of the patients, and Kellgren–Lawrence grading of the knee radiograph. We hypothesized that females, those aged more than 60 years [28], those having a BMI greater than 25 kg/m2, and those with more severe radiographic grading would have significant differences [10]. An independent -test was used to analyze for gender, BMI, and age groups of the patients. One-way ANOVA test was used to analyze radiographic grading based on Kellgren–Lawrence classification. In the analysis for known group validity, the score for each domain was normalized to 0–100.
3. Results
3.1. Translation and Cultural Adaptation
We found that all the items in the Malay version questionnaire are relevant and appropriate to the Malaysian population. All the items were found to be acceptable, clear, and easy to understand in the face validity.
3.2. Psychometric Properties
A total of 191 patients participated in the study. The sociodemographic and knee OA disease characteristics of the participants are shown in Table 1. The mean age was 57.8 (6.8) years and the majority were female. The Kellgren–Lawrence classification ranged from grade 0 to 4.
3.3. Descriptive Statistics of the Items
The items in the five constructs of OAKHQOL had missing data ranging from 0 to 3 values (0%–1.5%). However, the individual items concerning professional life, relationships, and sexual activities had 10 to 13 missing values. The missing values were replaced with the mean scores for the domain during the CFA. Normality assessment was done for the 40 items in the five constructs using histogram, box-plot, and measurement of skewness, which showed normal distribution. The absolute and percentage frequencies of the score for all the items were calculated and illustrated in Table 2.
3.4. Confirmatory Analysis
Confirmatory factor analysis was performed with one-step strategy. Confirmatory analysis showed that the original five-factor model of the OAKHQOL (40 items) was not fit (Table 3). Five items (py25, m36, m37, m38, and m16) were removed one by one due to low factor loadings, as shown in Model A. Eight items were set as free parameter estimates, one pair at a time (py1-py2, py7-py8, py4-py5, and pn34-pn33), based on high MI (greater than 15) as shown in Model C. Further item deletion was done based on MI and factor loadings (py3, py9, m29, py24, sp39, py14, and py13) until the final model, which consists of a five factors with 28 items, signified a model fit (Table 3). The final model consists of five constructs: physical activity (10 items), mental health (eight items), social functioning (three items), social support (three items), and pain (four items). Six items in the physical activity, five items in the mental health, and one item in the social support were removed. The goodness of fit indices indicated that the model had a good construct (CFI = 0.915, TLI = 0.905, IFI = 0.916, chi-squared/degree of freedom = 1.953, and RMSEA = 0.071) (Table 3).
The initial model before fit was shown in Figure 1. The correlation between factors was illustrated in Figure 2. The standardized factor loadings were from 0.5 to 0.9, indicating that all items contributed highly to the construct measures. The MI values were less than 10, and the correlation between each pair of latent constructs was less than 0.85, which is acceptable (Figure 2) [19].
3.5. Reliability
The reliability analysis showed that the Cronbach’s alpha coefficient value for each construct was greater than 0.7 (Table 4). The CR and AVE of each construct also showed that the final construct had a good measure of reliability. The result was achieved by using one-step estimation strategy.
Table 5 shows the Pearson’s correlation coefficients between the physical activity construct of the OAKHQOL and the functional construct of the WOMAC ( = 0.72) and between the pain construct of the OAKHQOL and pain construct of the WOMAC ( = 0.55). These results indicated that the OAKHQOL had acceptable criterion validity.
3.6. Known Group Validity
The results for the known group validity of the OAKHQOL are shown in Table 6. We found significant differences among the BMI groups (BMI ≤ 25 kg/m2 and >25 kg/m2) in the physical activity ( = 0.009), mental ( = 0.040), and pain domains ( = 0.009). We also found significant differences among the groups based on OA severity according to radiographic grading in the physical activity ( = 0.002) and pain domains ( = 0.043). Thus, groups who had greater disease severity based on radiography had worse scores. The scores of the pain domain for the age groups (age ≤ 60 years compared to those age > 60 years) were also significant. There were no differences observed for the social support and social function domains.
4. Discussion
Recently, validated health-related quality of life that accurately reflects a patient’s experience with respect to specific disease has been an important outcome recommended for interventional study. Health-related quality of life is a broad concept representing individual responses to physical, mental, and social effects on daily living. Therefore, the need to assess conceptual relevance and psychometric properties in various cultures or countries is increasing [15].
The present study indicated that the shortened Malay version of the OAKHQOL had good validity and reliability and is culturally acceptable. EFA of the original OAKHQOL using principle component analysis with orthogonal varimax rotation revealed four factors: physical activities, mental health, social support, and social functioning with the pain factor as an individual dimension [10, 15]. The OAKHQOL has also been validated in Spanish and Persian [2, 29]. However, to our knowledge, this is the first study that used confirmatory analysis in the validation analysis. CFA is used to verify the factor structure of a measurement instrument. CFA has become more commonly used for construct validation and to provide evidence for convergent and discriminant validity of the theoretical construct [30]. Furthermore, CFA is a theory-testing model and it starts with a hypothesis prior to the analysis which is based on strong theoretical and/or empirical foundation [31]. On the other hand, EFA is used to explore the possible underlying factor structure of a measurement instrument [32].
The panel in this study decided to keep the original five-factor model in the initial analysis, although the EFA of the original study did not support this. EFA of the original study was done in other language; thus the result was different. The decision to keep the pain construct in the final model was made because we found the pain factor to be an important domain that is also available in and consistent with other health-related QOL for OA measures and the items were also culturally acceptable [16, 17].
We made the decision to remove six items from the physical activity construct (py3, py9, py13, py14, py24, and py25), five items in the mental health construct (m16, m29, m36, m37, and m38), and one item in the social support construct (sp39) because other items in the construct reflected similar functions. Most of the items were removed because of significant overlapping (high modification indices) and lack of discrimination within the items. Removal of these items was shown to improve the fit indices of the model, indicating that perhaps they poorly represented the construct being measured. However, the panel of this study had also revisited and reviewed the items before they were removed because they might represent important and meaningful construct as mentioned in a previous validation study.
The reliability analysis showed that internal consistency of the Malay version OAKHQOL was acceptable. Other than that, the CR and AVE for each construct were also acceptable, indicating that they had good levels of internal consistency. As for the criterion validity, the analysis showed that the physical and pain constructs of the Malay version of OAKHQOL had good correlations with the functional and pain constructs of the WOMAC. In Malay version of OAKHQOL, physical activity construct has 10 items whereas WOMAC has 17 items in functional construct [16]. In physical activity and functional construct of both questionnaires, daily activities such as difficulty in walking, bending, going up and down the stairs, and getting in and out of a car or a bus were assessed. Physical activity on self-care such as taking bath, getting dressed, and cutting toe-nails was assessed in OAKHQOL, whereas WOMAC assessed other aspects of daily activities such as difficulty in sitting, standing, lying on bed, getting up from sitting or from bed, shopping, and also doing house chores [16]. Perhaps future research can examine the criterion validity for the mental construct, social functioning, and social support of the Malay version of OAKHQOL. The SF36 is one questionnaire that has been used to assess health-related QOL for people with knee OA, although it is not disease-specific. This questionnaire has been validated in the Malay language. We suggest correlating the OAKHQOL scores with the SF36 in a future study.
For the known group validity, we found that the Malay version of OAKHQOL discriminates well for the BMI groups and the severity of disease based on plain radiograph for the physical activity, pain, and mental domains. However, for the social domains, it was not discriminative based on disease severity. This finding was similar to the findings of De Tejada et al., who conducted the validation study in Spanish [2]. Both Malay and English versions after validation are shown in Tables 9 and 10.
This study is not without limitation. First, this study involved only people with knee OA; therefore, the findings may not be generalized to patients with hip OA. In addition, the convenient sampling was applied. Thus, it may not represent the true knee OA population in the community. It is also good to measure the responsiveness of this questionnaire in a clinical trial where it can be used to evaluate changes in patient status following therapeutic intervention.
5. Conclusion
The Malay version of OAKHQOL consisting of five factors assessed through 28 items was valid, reliable, and acceptable to measure quality of life in Malaysian population with knee OA.
Ethical Approval
This study protocol was approved by the Research Ethics Committee (Human), School of Medical Sciences, Universiti Sains Malaysia (FWA Reg. no. 00007718; IRB Reg. no. 00004494) and procedures followed were in accordance with the Helsinki Declaration of 1975.
Consent
The participants involved in the study have signed consent form to participate in the study.
Disclosure
An earlier version of this work was presented as a poster at the Medical Journal of Malaysia in 4th Asia Pacific Conference on Public Health.
Conflicts of Interest
The authors declare that there are no conflicts of interest regarding the publication of this article.
Acknowledgments
The authors would like to acknowledge the Universiti Sains Malaysia for the Grant (1001/PPSP/812132) to conduct this study. They also gratefully acknowledge the cooperation of all participating subjects and staff involved in this project. The authors would like to acknowledge the questionnaire’s author Anne-Christine Rat for giving them permission to use the OAKHQOL as well as a copy of the original English version.