Abstract
PURPOSE: To linguistically and culturally adapt the 31-item Singaporean Diabetic Retinopathy Knowledge and Attitudes (DRKA) questionnaire for a Chinese population and assess its reliability and validity using classical and modern psychometric theory. METHODS: A total of 230 patients with diabetic retinopathy (DR) were recruited, and of these, 202 valid responses were analyzed. Rasch analysis and classical test theory (CTT) methods were used to analyze the fit statistics of the Knowledge (n = 22 items) and Attitudes (n = 9 items) scales, including the functionality of the response categories, fit statistics, person and item reliability and separation, unidimensionality, targeting, differential item functioning (DIF), internal consistency, convergent validity, and known-group validity. RESULTS: After revision, both the Knowledge and Attitudes scales were unidimensional and had good measurement precision (Person Separation Index = 2.18 and 1.72) and internal consistency (Cronbach's α = 0.83 and 0.82). While the items in the Knowledge scale aptly targeted participants' ability level, targeting of the Attitudes scale was slightly suboptimal, with items too easy on average for participants' ability level. There were no issues with DIF and item fit, and the scales showed good known-group validity (scores increased as education level increased) and convergent validity (high correlation with the DRKA Practice questionnaire). CONCLUSIONS: After a thorough language and cultural verification process, the Chinese version of the DRKA is culturally appropriate and has good psychometric performance. TRANSLATIONAL RELEVANCE: The DRKA questionnaire may be useful to assess patients' DR-related knowledge and attitude level, as well as inform specific education interventions and optimize patients' ability to manage their condition.