Adding two culture-specific ‘bolt-on’ dimensions on the Thai version of EQ-5D-5L: an exploratory study in patients with diabetes

ABSTRACT

Background: This study explored whether addition of culture-specific bolt-on dimensions, ‘interpersonal relationships (IR)’ and ‘activities related to bending knees (AK)’ improves the relevance and validity of the EQ-5D among Thai patients with diabetes.

Methods: A cross-sectional study was conducted among 200 diabetic patients. Ceiling/floor effects, known-groups validity and test-retest reliability were evaluated. Hierarchical multiple regressions was performed to evaluate the incremental value of the EQ-5D+AK+IR over the EQ-5D-5L in predicting utility measured by visual analog scale (VAS).

Results: The EQ-5D+AK+IR reduced ceiling effects by 34%. For known-groups validity, women and lower educated patients reported more AK problems (p-value< 0.05); however, none of the IR dimension hypotheses were supported. Both IR and AK had the weighted kappa coefficients of 0.49, indicating good reliability. Hierarchical multiple regression found that adding AK (adjusted r²: 0.182 vs 0.156), but not IR (adjusted r²: 0.157 vs 0.156) significantly increased the explained variance in VAS score.

Conclusion: Preliminary findings suggest that AK, but not IR, may be a useful addition to the EQ-5D questionnaire for use with Thai patients. Further studies in diverse populations are needed to examine the impacts of the proposed new dimensions and determine if these cultural adaptations are justified.

KEYWORDS:

• Bolt-on
• culture
• EQ-5D
• health-related quality of life
• psychometric properties

Acknowledgments

The authors would like to express our gratitude to the EuroQoL group for allowing us to conduct this study. We are grateful to Dr. A. Simon Pickard for his invaluable advice and comments regarding data analyses of this study. We would like to thank Mrs. Soontraporn Phipadthakusolkul and interviewers for assistance with data collection as well as all patients for their participation in this study.

Declaration of Interest

K Kangwanrattanakul was granted by the Thailand Research Fund through the Royal Golden Jubilee Ph.D. Program, which had no role in the study. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer Disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Availability of data and materials

The data analyzed and reported in this manuscript is not available for public sharing. Moreover, this publication is a part of the degree of Doctor of Philosophy in Social, Economic and Administrative Pharmacy, Faculty of Graduate Studies, Mahidol University.

Ethics approval and consent to participate

This study was approved by the Mahidol University Institutional Review Board (MU-IRB):PY-IRB 2015/016.1004, and Rhamathibodi Hospital Review Board, Thailand. Informed consents were obtained from all patients.

Author contributions

The study was jointly designed by KR, CRG, MS and MT. KR involved in data collection. Data analyses were performed by KR and rechecked by CRG, MS and MT. All authors were involved in drafting, revising and the final approval of this manuscript.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This study was fully funded through the Royal Golden Jubilee (RGJ) Ph.D. Programme in Thailand under Grant Number: PHD/0115/2556 provided by the Thailand Research Fund (TRF) and Mahidol University. However, the results and opinions reported in this manuscript have not been endorsed by the grant.