Stomach Flu

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When used in patients with gastroesophageal reflux disease (GERD) before and after 4 weeks’ acid-suppressive therapy, the English language version of the Work Productivity and Impairment questionnaire in patients with GERD (WPAI-GERD) demonstrates responsiveness to change and good cross-sectional construct validity. Results indicate that the instrument may demonstrate poor longitudinal construct validity, an issue that warrants further investigation.

Key findings

The English language version of the WPAI-GERD is responsive to change and demonstrates good cross-sectional construct validity.Results indicate that the instrument may demonstrate poor longitudinal construct validity, an issue that warrants further investigation.Extended abstract
Background: The Work Productivity and Impairment (WPAI) questionnaire is one of the most frequently used instruments for assessing health-related productivity. The WPAI questionnaire for patients with gastroesophageal reflux disease (WPAI-GERD), for example, uses single-item questions to assess GERD-related absence from work, reduced productivity while at work and reduced productivity in daily activities. The WPAI-GERD has demonstrated high cross-sectional validity in Swedish patients with GERD.

Aim: To assess responsiveness to change and construct validity of the English language version of the WPAI-GERD questionnaire.

Methods: Canadian patients with a symptoms-based diagnosis of GERD were enrolled. Patients were required to have been symptomatic for ≥3 months, to have experienced heartburn for ≥4 days during the previous 7 days and to report at least moderate problems over the previous 7 days. Patients answered a battery of health-related quality-of-life instruments, including the WPAI-GERD, before and after 4 weeks’ acid-suppressive therapy (esomeprazole 40 mg once daily). The WPAI-GERD in this study included one question on total days worked and one on days worked with GERD symptoms, followed by three questions on work time: hours absent from work due to GERD symptoms; hours absent from work due to other reasons; and hours actually worked. The final questions related to average percentage reduced productivity due to GERD symptoms while working and average percentage reduced productivity while doing other activities (housework, schoolwork, leisure-time activities etc). Mean change from baseline in the productivity variables was calculated, along with construct validity and responsiveness to change.

Results: In total, 217 patients were included in this analysis, of which 153 (71%) were employed. At baseline, patients reported a mean of 0.9 hours (95% confidence interval [CI]: 0.4, 1.3) GERD-related absence from work and 14% (95% CI: 11.0, 17.0) reduced productivity during the previous week (equivalent of 5.8 hours), as well as 21% (95% CI: 17.9, 24.0) reduction in daily activities. After 4 weeks’ treatment, the number of hours absent from work due to GERD symptoms reduced to 0.3 hours (95% CI: 0.1, 0.5) and the percentage reduction in work productivity decreased to 3% (95% CI: 1.8, 4.2; corresponding to 1.1 hours). Similarly, the percentage reduction in productivity in activities other than work was 4.9% (95% CI: 3.4, 6.3) after treatment. Changes from baseline were significant (Table 1).
Cross-sectional correlation coefficients (which are used to assess validity at one measured timepoint) between productivity variables and health-related quality of life ranged from 0.02 to 0.65. For productivity variables and symptoms, the correlation ranged from 0.04 to 0.63. In terms of longitudinal construct validity (which is used to assess change between two measurements), correlations were 0.05 to 0.56 between WPAI variables and health-related quality of life (supporting longitudinal construct validity) while they were 0.06 to 0.34 for WPAI variables and symptoms (indicating poor longitudinal construct validity). The WPAI-GERD demonstrated responsiveness to change.

Conclusions: The English language version of the WPAI-GERD questionnaire demonstrated responsiveness to change and cross-sectional construct validity. While results suggest that the longitudinal construct validity of the English WPAI-GERD may be poor, the overall findings suggest that further study of this instrument is warranted.

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