Do English and Chinese EQ-5D versions demonstrate measurement equivalence? an exploratory study
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Do English and Chinese EQ-5D versions demonstrate measurement equivalence? an exploratory study Nan Luo1, Ling-Huo Chew2, Kok-Yong Fong3,4, Dow-Rhoon Koh3,4, SweeCheng Ng4, Kam-Hon Yoon3,4, Sheila Vasoo4, Shu-Chuen Li1 and Julian Thumboo*3,4 Address: 1Department of Pharmacy, National University of Singapore, Singapore, 2School of Health Sciences, Nanyang Polytechnic, Singapore, 3Department of Medicine, National University of Singapore, Singapore and 4Department of Medicine, National University Hospital, Singapore Email: Nan Luo - [email protected]; Ling-Huo Chew - [email protected]; Kok-Yong Fong - [email protected]; DowRhoon Koh - [email protected]; Swee-Cheng Ng - [email protected]; Kam-Hon Yoon - [email protected]; Sheila Vasoo - [email protected]; Shu-Chuen Li - [email protected]; Julian Thumboo* - [email protected] * Corresponding author
Published: 17 April 2003 Health and Quality of Life Outcomes 2003, 1:7
Received: 11 March 2003 Accepted: 17 April 2003
This article is available from: http://www.hqlo.com/content/1/1/7 © 2003 Luo et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.
Abstract Background: Although multiple language versions of health-related quality of life instruments are often used interchangeably in clinical research, the measurement equivalence of these versions (especially using alphabet vs pictogram-based languages) has rarely been assessed. We therefore investigated the measurement equivalence of English and Chinese versions of the EQ-5D, a widely used utility-based outcome instrument. Methods: In a cross-sectional study, either EQ-5D version was administered to consecutive outpatients with rheumatic diseases. Measurement equivalence of EQ-5D item responses and utility and visual analog scale (EQ-VAS) scores between these versions was assessed using multiple regression models (with and without adjusting for potential confounding variables), by comparing the 95% confidence interval (95%CI) of score differences between these versions with pre-defined equivalence margins. An equivalence margin defined a magnitude of score differences (10% and 5% of entire score ranges for item responses and utility/EQ-VAS scores, respectively) which was felt to be clinically unimportant. Results: Sixty-six subjects completed the English and 48 subjects the Chinese EQ-5D. The 95%CI of the score differences between these versions overlapped with but did not fall completely within pre-defined equivalence margins for 4 EQ-5D items, utility and EQ-VAS scores. For example, the 95%CI of the adjusted score difference between these EQ-5D versions was -0.14 to +0.03 points for utility scores and -11.6 to +3.3 points for EQ-VAS scores (equivalence margins of -0.05 to +0.05 and -5.0 to +5.0 respectively). Conclusion: These data provide promising evidence for the measurement equivalence
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