Publication
Title
The psychometric properties of the psoriasis disability index in United States patients
Author
Abstract
Although it has had only limited psychometric assessment in one country (the UK), the Psoriasis Disability Index (PDI) is a commonly used measure of the impact of psoriasis on patients. This study's objective was to analyze the psychometric properties of the PDI in 1196 US patients. High Cronbach's alpha coefficients suggested that the PDI's internal consistency is good. The validity of the PDI was tested using a global question on disease burden and self-assessed extent of disease and both appeared to be good predictors of the PDI. Large floor effects and the suboptimal response distribution of most items, however, suggested that the PDI is insensitive to mild functional limitation. Factor analyses indicated that the current PDI subscales are suboptimal. In the Rasch analysis, the PDI and its subscales appeared to measure multiple constructs, making the validity of deriving a single overall score questionable. The frequent presence of differential item functioning related to several patient characteristics confirmed the instrument's multidimensionality. These findings suggest that the PDI is not an optimal measure for use in US study populations. The psychometric properties of instruments designed to measure the impact of psoriasis should be tested in populations in which the instrument is to be applied.
Language
English
Source (journal)
The journal of investigative dermatology. - Baltimore, Md
Publication
Baltimore, Md : 2005
ISSN
0022-202X
Volume/pages
125:4(2005), p. 665-672
ISI
000232556700009
Full text (Publisher's DOI)
Full text (publisher's version - intranet only)
UAntwerpen
Faculty/Department
Research group
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identification
Creation 03.01.2013
Last edited 10.06.2017
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