Published in:
01-05-2007 | Original Research Article
The Work Productivity and Activity Impairment Questionnaire for Patients with Gastroesophageal Reflux Disease (WPAI-GERD)
Responsiveness to Change and English Language Validation
Published in: PharmacoEconomics | Issue 5/2007
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Background
A validated productivity questionnaire, the Work Productivity and Activity Impairment questionnaire for Gastroesophageal Reflux Disease (WPAIGERD), exists for Swedish patients with GERD.
Objective
To assess responsiveness to change of the WPAI-GERD and construct validity of the English language version.
Methods
We used the WPAI-GERD in a before-after treatment clinical study of Canadian GERD patients with moderate or severe symptoms treated with esomeprazole 40mg once daily for 4 weeks. We measured productivity variables including GERD-specific absence from work, reduced productivity while at work and reduced productivity while carrying out regular daily activities other than work during the preceding week.
Results
The analysis included 217 patients, of whom 71% (n = 153) were employed. Before treatment, employed patients reported an average 0.9 hours of absence from work due to GERD and 14.0% reduced work productivity (5.8 hours equivalent) in the previous week, as well as 21.0% reduced productivity in daily activities (all patients). After treatment, the corresponding figures decreased to 0.3 hours, 3.0% (1.1 hours equivalent) and 4.9%, respectively. Thus, the improvement (difference from start of treatment) in productivity was 0.6 hours (p = 0.011) for absence from work and 11.0% units (p < 0.001) for reduced work productivity (4.7 hours equivalent, p < 0.001). This translated into an avoided loss of work productivity of 5.3 hours in total on a weekly basis per employed patient. In addition, a 16.1% unit (p < 0.001) improvement for reduced productivity in activities was observed.
Cross-sectional correlation coefficients of WPAI variables with symptoms (range 0.04–0.63) and health-related quality of life (HR-QOL; range 0.02–0.65) supported cross-sectional construct validity. Corresponding change score correlations between WPAI variables and HR-QOL (range 0.0520.56) supported longitudinal construct validity of the WPAI-GERD while low change score correlations between productivity variables and relevant symptoms (range 0.06–0.34) did not.
Conclusion
The English version of the WPAI-GERD showed good cross-sectional construct validity, and results indicated that the WPAI-GERD is responsive to change. Although the results also indicated that longitudinal construct validity may be poor, the overall findings suggest that further study of the instrument remains warranted.