Abstract
Choosing between preference-based instruments of health-related quality of life (HR-QOL) in particular situations is an important area for research. Even where instruments can be assumed to be measuring the same thing, they may not be interchangeable. The study presented investigates the extent to which EQ-5D and SF-6D instruments are interchangeable in an older, chronically ill patient group undergoing haemodialysis. Head-to-head comparisons were made using ‘practicality’, ‘descriptive validity’, ‘empirical validity’, mean utilities and associated distributions. Overall it was difficult to choose between instruments on the basis of descriptive or empirical validity, since both performed similarly. Important differences were, however, found relating to practicality: a significantly higher response rate in favour of EQ-5D; and lower levels of missing data to derive health states. Non-response was significantly associated with age and co-morbidity of respondents. We suggest that in patients undergoing haemodialysis, and potentially other older chronically ill patient groups, EQ-5D is the primary preference-based generic HR-QOL instrument.
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Acknowledgements
We are grateful to the other members of the National Renal Satellite Evaluation Group, patients and hospital staff from the 24 units that participated in the study. We are also grateful for comments received at a Health Economists’ Study Group meeting and from Professor Gavin Mooney. The NHS R&D Health Technology Assessment Programme funded the project. The views expressed in this paper and any errors are those of the authors alone. There are no conflicts of interest relevant to this article.
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Appendices
Appendices
Appendix 1
Refer to table A1.
EQ-5D and SF-6D classification systems
Appendix 2
Refer to table A2.
Matching selected SF-6D domain levels to EQ-5D levels
Appendix 3: Details of Statistical Analyses
Weighted Kappa scores tested the level of agreement for the first set of construct validity tests. Following standard practice five categories of agreement were used to interpret the Kappa scores: ‘poor’ =<0.2; ‘fair’ =0.21-0.4; ‘moderate’ = 0.41−0.6; ‘good’ =0.61−0.8; and 0.81−1.0 = ‘very good’.[29] These interpretations were also applied to the correlation coefficients.
The Chi-square test of association was used for categorical data; the Mann-Whitney U test to compare two groups; and the Jonckheere-Terpestra test to assess trends for ordered categorical data. Given that multiple statistical tests were undertaken, even those found to be statistically significant need cautious interpretation.
A Bonferroni correction was not used as this might have been overly conservative in what was an exploratory study.
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Gerard, K., Nicholson, T., Mullee, M. et al. EQ-5D versus SF-6D in an older, chronically ill patient group. Appl Health Econ Health Policy 3, 91–102 (2004). https://doi.org/10.2165/00148365-200403020-00005
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DOI: https://doi.org/10.2165/00148365-200403020-00005