University of Massachusetts Medical School Faculty Publications

UMMS Affiliation

Department of Quantitative Health Sciences; Graduate School of Biomedical Sciences, Clinical and Population Health Research Program

Publication Date

2013-11-15

Document Type

Article

Disciplines

Health Services Research | Musculoskeletal Diseases

Abstract

BACKGROUND: The SF-36 physical functioning scale (PF-10) and the Health Assessment Questionnaire disability index (HAQ-DI) are the most frequently used instruments for measuring self-reported physical function in rheumatoid arthritis (RA). The objective of this study was to develop a crosswalk between scores on the PF-10 and HAQ-DI in RA.

METHODS: Item response theory (IRT) methods were used to co-calibrate both scales using data from 1791 RA patients. The appropriateness of a Rasch-based crosswalk was evaluated by comparing it with crosswalks based on a two-parameter and a multi-dimensional IRT model. The accuracy of the final crosswalk was cross-validated using baseline (n = 532) and 6-month follow-up (n = 276) data from an independent cohort of early RA patients.

RESULTS: The PF-10 and HAQ-DI adequately fit a unidimensional Rasch model. Both scales measured a wide range of functioning, although the HAQ-DI tended to better target lower levels of functioning. The Rasch-based crosswalk performed similarly to crosswalks based on the two-parameter and multidimensional IRT models. Agreement between predicted and observed scale scores in the cross-validation sample was acceptable for group-level comparisons. The longitudinal validity in discriminating between disease response states was similar between observed and predicted scores.

CONCLUSION: The crosswalk developed in this study allows for converting scores from one scale to the other and can be used for group-level analyses in patients with RA.

Keywords

Health assessment questionnaire, Item response theory, Linking, Physical functioning, Rheumatoid arthritis, Short form 36-item health survey (SF-36)

Rights and Permissions

Copyright 2013 ten Klooster et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

DOI of Published Version

10.1186/1477-7525-11-199

Source

ten Klooster PM, Oude Voshaar MA, Gandek B, Rose M, Bjorner JB, Taal E, Glas CA, van Riel PL, van de Laar MA. Development and evaluation of a crosswalk between the SF-36 physical functioning scale and Health Assessment Questionnaire disability index in rheumatoid arthritis. Health Qual Life Outcomes. 2013 Nov 15;11:199. doi: 10.1186/1477-7525-11-199. Link to article on publisher's site

Comments

Co-author Barbara Gandek is a doctoral student in the Clinical and Population Health Research program in the Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.

Related Resources

Link to Article in PubMed

Journal/Book/Conference Title

Health and quality of life outcomes

PubMed ID

24229416

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