Developing a New Version of the SF-6D Health State Classification System From the SF-36v2: SF-6Dv2

John E. Brazier, Brendan J. Mulhern, Jakob B. Bjorner, Barbara Gandek, Donna Rowen, Jordi Alonso, Gemma Vilagut, John E. Ware, SF-6Dv2 International Project Group

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Abstract

OBJECTIVE: The objective of this study was to develop the classification system for version of the SF-6D (SF-6Dv2) from the SF-36v2. SF-6Dv2 is an improved version of SF-6D, one of the most widely used generic measures of health for the calculation of quality-adjusted life years. STUDY DESIGN AND SETTING: A 3-step process was undertaken to generate a new classification system: (1) factor analysis to establish dimensionality; (2) Rasch analysis to understand item performance; and (3) tests of differential item function. To evaluate robustness, Rasch analyses were performed in multiple subsets of 2 large cross-sectional datasets from recently discharged hospital patients and online patient samples. RESULTS: On the basis of factor analysis, other psychometric evidence, cross-cultural considerations, and amenability to valuation, the 6-dimension classification used in SF-6D was maintained. SF-6Dv2 resulted in the following modifications to SF-6D: a simpler classification of physical function with clearer separation between levels; a more detailed 5-level description of role limitations; using negative wording to describe vitality; and using pain severity rather than pain interference. CONCLUSIONS: The SF-6Dv2 classification system describes more distinct levels of health than SF-6D, changes the descriptions used for a number of dimensions and provides clearer wording for health state valuation. The second stage of the study has developed a utility value set using discrete choice methods so that the measure can be used in health technology assessment. Further work should investigate the psychometric characteristics of the new instrument.

Original languageEnglish
JournalMedical Care
Volume58
Issue number6
Pages (from-to)557-565
Number of pages9
ISSN0025-7079
DOIs
Publication statusPublished - 2020

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