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Validity of the Workers Productivity and Activity Impairment Questionnaire: Specific Health Problem (WPAI:SHP) in patients with systemic sclerosis
Methods: SSc patients, identified through the Australian Scleroderma Cohort Study database, completed the WPAI:SHP and a quality of life instrument (PROMIS-29) cross-sectionally. The construct validity of the WPAI:SHP was assessed by the correlations between the WPAI:SHP and a range of SSc health states. Non-parametric correlation, including Spearman's correlation (ρ), was used to test the validity of WPAI:SHP and ability to distinguish between different health states.
Results: A total of 476 completed questionnaires was returned, equating to a response rate of 63.7%. Among those under 65 years of age, 155 patients (55.2%) were in paid employment. Employed patients had a mean (± SD) age of 56.5 (9.8) years and were predominantly female (87.3%) with limited disease subtype (75.6%). The WPAI:SHP showed construct validity based on moderate to strong correlations with health status as assessed by a range of health outcome measures including disease activity (ρ = 0.34-0.39, p = 0.001), physical function (ρ = 0.55-0.62, p = 0.001), disease severity (ρ = 0.55-0.62, p = 0.001), fatigue (ρ = 0.62-0.63, p = 0.001), pain (ρ = 0.68-0.71, p = 0.001), and breathlessness (ρ = 0.39-0.46, p = 0.001). Furthermore, according to the effect size, the WPAI:SHP scores have a large discriminative ability (d = 1.26-1.47) for distinguishing SSc patients with different health outcomes.
Conclusions: The WPAI is a valid questionnaire for assessing impairments in paid employment and social activities in SSc patients, and for measuring the relative differences between SSc patients with varying health states.
History
Publication title
Clinical and Experimental RheumatologyVolume
35Issue
Suppl 106Pagination
S130-S137ISSN
0392-856XDepartment/School
Menzies Institute for Medical ResearchPublisher
Clinical & Exper RheumatologyPlace of publication
Via Santa Maria 31, Pisa, Italy, 56126Rights statement
© Clinical and Experimental RheumatologyRepository Status
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