Differential item functioning in quality of life measurement:an analysis using anchoring vignettes

Knott, Rachel J. and Lorgelly, Paula K. and Black, Nicole and Hollingsworth, Bruce (2017) Differential item functioning in quality of life measurement:an analysis using anchoring vignettes. Social Science and Medicine, 190. pp. 247-255. ISSN 0277-9536

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Abstract

Systematic differences in the ways that people use and interpret response categories (differential item functioning, DIF) can introduce bias when using self-assessments to compare health or quality of life across heterogeneous groups. This paper reports on an exploratory analysis involving the use of anchoring vignettes to identify differential item functioning (DIF) in a commonly used measure for assessing health-related quality of life - namely the EQ-5D. Using data from a bespoke (i.e. custom) survey that recruited a representative sample of 4300 respondents from the general Australian population in 2014 and 2015, we find that the assumptions of response consistency (RC) and vignette equivalence (VE) hold in a sub-sample of respondents aged 55–65 years (n = 914), which demonstrates that vignettes can appropriately identify DIF in EQ-5D reporting for this age group. We find that the EQ-5D is indeed subject to DIF, and that failure to account for DIF can lead to conclusions that are misleading when using the instrument to compare health or quality of life across heterogeneous groups. We also provide several important insights in terms of the identifying assumptions of RC and VE. We conclude that the implications of DIF could be of considerable importance, not only for outcomes research, but for funding decisions in healthcare more broadly given the strong reliance on patient-reported outcome measures in economic evaluations for health technology assessment.

Item Type:
Journal Article
Journal or Publication Title:
Social Science and Medicine
Additional Information:
This is the author’s version of a work that was accepted for publication in Social Science & Medicine. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Social Science & Medicine, 190, 2017 DOI: 10.1016/j.socscimed.2017.08.033
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/3300/3306
Subjects:
ID Code:
87483
Deposited By:
Deposited On:
30 Aug 2017 09:20
Refereed?:
Yes
Published?:
Published
Last Modified:
01 Dec 2020 04:54