Work, Classroom and Activity Impairment Instruments
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The validity and responsiveness of allergy-specific questions in the format of the Work Productivity and Activity Impairment (WPAI) questionnaire were tested, and the work, activity and classroom impairment of allergic rhinitis patients with moderate to severe allergy symptoms were described. Allergy-specific WPAI (WPAI-AS) instruments were completed at baseline and at week 1 and week 2 by patients in 2 multicentre, double-blind, randomised placebo-controlled clinical trials of antihistamines: terfenadine (work/activity impairment; n = 422) or fexofenadine (MDL 16,455A) [classroom impairment; n = 241]. The validity, responsiveness to clinical change, and reproducibility in the absence of clinical change of the WPAI-AS were measured independently by symptom severity scores. Allergy symptoms were associated with impairment at work, at other regular activities, and in the classroom. The studies established the discriminative and evaluative validity, reproducibility and responsiveness of WPAI-AS measures of work impairment, overall work impairment, activity impairment and classroom impairment secondary to allergy symptoms, but not of work or classroom time missed. To detect a 5% difference in impairment, with 80% power and 5% type I error for a 2-sided hypothesis test (change from baseline to weeks 1 and 2 combined) would require 201 patients/treatment group (overall work impairment), and 192 patients/treatment group (overall classroom impairment).
These results validate the WPAI-AS as tools in quality-of-life analysis of allergic rhinitis and provide data for selecting an adequate sample size to differentiate interventions in controlled studies measuring changes in work, activity and classroom impairment secondary to allergic rhinitis symptoms.
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