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Title: A cultural adaptation and validation study of a self-report measure of the extent of and reasons for medication nonadherence among patients with diabetes in Singapore
Authors: Liau, Y.W.
Cheow, C.
Leung, K.T.Y.
Tan, H.
Low, S.F.
Cheen, H.H.M.
Lim, W.C.
Tan, L.L.
Tan, J.Z.Y.
Lee, E.S.
Xu, S.J.
Tan, C.Y.K.
Phang, J.W.
Phang, J.K.
Lam, M.H.
Blalock, D.V.
Voils, C.I.
Yap, K.Z. 
Kwan, Y.H.
Keywords: Adherence
Patient-reported outcome
Quality of life
Issue Date: 2019
Publisher: Dove Medical Press Ltd.
Citation: Liau, Y.W., Cheow, C., Leung, K.T.Y., Tan, H., Low, S.F., Cheen, H.H.M., Lim, W.C., Tan, L.L., Tan, J.Z.Y., Lee, E.S., Xu, S.J., Tan, C.Y.K., Phang, J.W., Phang, J.K., Lam, M.H., Blalock, D.V., Voils, C.I., Yap, K.Z., Kwan, Y.H. (2019). A cultural adaptation and validation study of a self-report measure of the extent of and reasons for medication nonadherence among patients with diabetes in Singapore. Patient Preference and Adherence 13 : 1241-1252. ScholarBank@NUS Repository.
Rights: Attribution-NonCommercial 4.0 International
Abstract: Background: This self-report measure is a new instrument to measure the extent of and reasons for medication adherence separately. However, few studies have assessed its psychometric properties in diabetic patients and also in Asian populations. Objectives: To validate this self-report measure in diabetic patients in Singapore. Methods: We collected data prospectively using a questionnaire among 393 diabetic patients from hospitals in Singapore from July 2018 to January 2019. Using the COnsensus-based Standards for the selection of health Measurement INstruments framework, we assessed face validity, internal consistency, test–retest reliability, structural validity, and measurement error. We tested four a priori hypotheses on correlation of extent score with patient-reported outcome measures to assess construct validity. We examined cross-cultural validity via measurement invariance across gender, age groups, and languages. Results: We performed cognitive interviews with 30 consenting English-literate, Chinese-literate, and Malay-literate (10 patients per language) diabetic patients (age range 48–76 years, 53% male, disease duration range 1–30 years) and face validity was supported. Among 393 patients (mean age: 59.4±12.2 years, 50.9% female, 52.4% Chinese), we showed moderate internal consistency (Cronbach’s alpha =0.67) and test–retest reliability (intra-class coefficient=0.56 [95% CI 0.37–0.70]). We calculated smallest detectable change as 0.80. We established construct validity by meeting all four hypotheses. We showed structural validity as confirmatory factor analysis confirmed a one-factor model, with excellent fit statistics (Comparative Fit Index=1.0; Tucker-Lewis Index=1.0; Root Mean Square Error of Approximation<0.001; Standardized Root Mean Residuals<0.001). Analysis of cross-cultural validity supported configural invariance model but not metric invariance and scalar invariance model. Caution must be taken against directly comparing extent scores across gender, age groups, and languages. Conclusion: This self-report measure is valid and reliable in measuring medication adherence in diabetic patients in Singapore. © 2019 Liau et al.
Source Title: Patient Preference and Adherence
ISSN: 1177889X
DOI: 10.2147/PPA.S208736
Rights: Attribution-NonCommercial 4.0 International
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