Psychometric validation of the Chinese version of the Difficulties in the daily life of patients with osteoarthritis of the knee
Authors: Hou Ailin , Ning Ning , Chen Jiali , Li Peifang , Xie Yan , Zhang Lin , Qu Junhong , Huang Cun 
Published: March 2023

Abstract
Background: The Difficulties in the Daily Life of patients with osteoarthritis of the knee Scale (DDLKOS) was developed in Japan to assess difficulties in daily living in KOA patients with appropriate psychometric properties. In mainland China, there is no validated assessment tool to evaluate difficulties in daily life for KOA patients. It is essential to introduce the DDLKOS in mainland China and to further explore its measurement properties. In this study, the DDLKOS was successfully adapted cross-culturally to provide a tool for assessing difficulties in daily life for Chinese KOA patients.
Methods: The Japanese version of the original DDLKOS scale was cross-culturally translated according to international Guidelines for the process of cross-cultural adaptation. Measurement properties (content validity, construct validity and reliability) were tested in accordance with the COSMIN checklists. A total of 450 patients were included in this study, and 40 participants with KOA participated a second visit two weeks later. Confirmatory factor analysis (CFA) and principal factor analysis (PCA) were applied to test the factor structure. Cronbach’s alpha and an intra-class correlation coefficient (ICC) were calculated for internal consistency and reproducibility. A methodological study of the translation and validation of the DDLKOS was conducted from April to December 2022. It involved three phases: (1) the translation and revision of the scale; (2) the exploration and evaluation of the item (n=180); (3) the psychometric evaluation of the scale (n=270).
Results: After a rigorous translation and revision, the Chinese version of DDLKOS with three dimensions and 14 items was finally formed. In this study, the critical ratios of the item ranged from 4.828 to 13.533, and the item-total correlation coefficients ranged from 0.577 to 0.690, and the factor loadings of the item ranged from 0.559 to 0.818. The content validity index (I-CVI) at the item level ranged from 0.818 to 1, and the content validity index (S-CVI) at the scale level was 0.909. For exploratory factor analysis, the three-factor structure explained the cumulative 60.019% of the overall variance. As the results of confirmatory factor analysis, all the recommended fitting indexes were appropriate. The average variance extracted values ranged from 0.589 to 0.702, and the composite reliability values ranged from 0.881 to 0.904. The total Cronbach’s α coefficient, split-half reliability coefficient and test–retest reliability coefficient of the scale were 0.814, 0.784 and 0.796, respectively. The results showed that the Chinese version of DDLKOS had an acceptable model fit superiority index and good structural validity.
Conclusion: The Chinese version of DDLKOS was successfully introduced into China, showing good psychometric properties among KOA patients, and can effectively assess the difficulties in the daily life ofKOA patient. Also, the adaption of DDLKOS can provide a basis for the development of self-management strategies for patients with knee osteoarthritis in China.