Differential item functioning (DIF) analyses of health-related quality of life instruments using logistic regression
- PDF / 328,123 Bytes
- 9 Pages / 595.276 x 793.701 pts Page_size
- 72 Downloads / 196 Views
RESEARCH
Open Access
Differential item functioning (DIF) analyses of health-related quality of life instruments using logistic regression Neil W Scott1*, Peter M Fayers1,2, Neil K Aaronson3, Andrew Bottomley4, Alexander de Graeff5, Mogens Groenvold6,7, Chad Gundy3, Michael Koller8, Morten A Petersen6, Mirjam AG Sprangers9, the EORTC Quality of Life Group and the Quality of Life Cross-Cultural Meta-Analysis Group
Abstract Background: Differential item functioning (DIF) methods can be used to determine whether different subgroups respond differently to particular items within a health-related quality of life (HRQoL) subscale, after allowing for overall subgroup differences in that scale. This article reviews issues that arise when testing for DIF in HRQoL instruments. We focus on logistic regression methods, which are often used because of their efficiency, simplicity and ease of application. Methods: A review of logistic regression DIF analyses in HRQoL was undertaken. Methodological articles from other fields and using other DIF methods were also included if considered relevant. Results: There are many competing approaches for the conduct of DIF analyses and many criteria for determining what constitutes significant DIF. DIF in short scales, as commonly found in HRQL instruments, may be more difficult to interpret. Qualitative methods may aid interpretation of such DIF analyses. Conclusions: A number of methodological choices must be made when applying logistic regression for DIF analyses, and many of these affect the results. We provide recommendations based on reviewing the current evidence. Although the focus is on logistic regression, many of our results should be applicable to DIF analyses in general. There is a need for more empirical and theoretical work in this area.
Background Many health-related quality of life (HRQoL) instruments contain multi-item scales. As part of the process of validating a HRQoL instrument it may be desirable to know whether each item behaves in the same way for different subgroups of respondents. For example, do males and females respond differently to a question about carrying heavy objects, even after accounting for their overall level of physical functioning? Is an item about fatigue answered similarly by older and younger age groups, given the same overall fatigue level? Does a translation of a questionnaire item behave in the same way as the original version? Differential item functioning (DIF) methods are a range of techniques that are * Correspondence: [email protected] 1 Section of Population Health, University of Aberdeen, UK Full list of author information is available at the end of the article
increasingly being used to evaluate whether different subgroups respond differently to particular items within a scale, after controlling for group differences in the overall HRQoL domain being assessed. DIF analyses were first used in educational testing settings to investigate whether particular items in a test were unfair to, for example, females or a particular ethnic g
Data Loading...
