TY - JOUR
T1 - The 12-item world health organization disability assessment schedule II (WHO-DAS II)
T2 - A nonparametric item response analysis
AU - Luciano, Juan V.
AU - Ayuso-Mateos, José L.
AU - Aguado, Jaume
AU - Fernandez, Ana
AU - Serrano-Blanco, Antoni
AU - Roca, Miquel
AU - Haro, Josep M.
N1 - Funding Information:
This study was funded by H. Lundbeck A/S, which was responsible for field work and collection of data. They did not have any role in the analysis and interpretation of data, in the writing of the manuscript, and in the decision to submit the manuscript for publication. JVL and AF are grateful to the "Instituto de Salud Carlos III" (Red RD06/0018/0017) for a postdoctoral and a predoctoral contract, respectively.
PY - 2010
Y1 - 2010
N2 - Background. Previous studies have analyzed the psychometric properties of the World Health Organization Disability Assessment Schedule II (WHO-DAS II) using classical omnibus measures of scale quality. These analyses are sample dependent and do not model item responses as a function of the underlying trait level. The main objective of this study was to examine the effectiveness of the WHO-DAS II items and their options in discriminating between changes in the underlying disability level by means of item response analyses. We also explored differential item functioning (DIF) in men and women. Methods. The participants were 3615 adult general practice patients from 17 regions of Spain, with a first diagnosed major depressive episode. The 12-item WHO-DAS II was administered by the general practitioners during the consultation. We used a non-parametric item response method (Kernel-Smoothing) implemented with the TestGraf software to examine the effectiveness of each item (item characteristic curves) and their options (option characteristic curves) in discriminating between changes in the underliying disability level. We examined composite DIF to know whether women had a higher probability than men of endorsing each item. Results. Item response analyses indicated that the twelve items forming the WHO-DAS II perform very well. All items were determined to provide good discrimination across varying standardized levels of the trait. The items also had option characteristic curves that showed good discrimination, given that each increasing option became more likely than the previous as a function of increasing trait level. No gender-related DIF was found on any of the items. Conclusions. All WHO-DAS II items were very good at assessing overall disability. Our results supported the appropriateness of the weights assigned to response option categories and showed an absence of gender differences in item functioning.
AB - Background. Previous studies have analyzed the psychometric properties of the World Health Organization Disability Assessment Schedule II (WHO-DAS II) using classical omnibus measures of scale quality. These analyses are sample dependent and do not model item responses as a function of the underlying trait level. The main objective of this study was to examine the effectiveness of the WHO-DAS II items and their options in discriminating between changes in the underlying disability level by means of item response analyses. We also explored differential item functioning (DIF) in men and women. Methods. The participants were 3615 adult general practice patients from 17 regions of Spain, with a first diagnosed major depressive episode. The 12-item WHO-DAS II was administered by the general practitioners during the consultation. We used a non-parametric item response method (Kernel-Smoothing) implemented with the TestGraf software to examine the effectiveness of each item (item characteristic curves) and their options (option characteristic curves) in discriminating between changes in the underliying disability level. We examined composite DIF to know whether women had a higher probability than men of endorsing each item. Results. Item response analyses indicated that the twelve items forming the WHO-DAS II perform very well. All items were determined to provide good discrimination across varying standardized levels of the trait. The items also had option characteristic curves that showed good discrimination, given that each increasing option became more likely than the previous as a function of increasing trait level. No gender-related DIF was found on any of the items. Conclusions. All WHO-DAS II items were very good at assessing overall disability. Our results supported the appropriateness of the weights assigned to response option categories and showed an absence of gender differences in item functioning.
UR - http://www.scopus.com/inward/record.url?scp=77952417230&partnerID=8YFLogxK
U2 - 10.1186/1471-2288-10-45
DO - 10.1186/1471-2288-10-45
M3 - Article
C2 - 20487526
AN - SCOPUS:77952417230
SN - 1471-2288
VL - 10
JO - BMC Medical Research Methodology
JF - BMC Medical Research Methodology
M1 - 45
ER -