Validation of the Spanish Work Productivity and Activity impairment questionnaire: Crohn's disease version.

BACKGROUND: The Work Productivity and Activity Impairment questionnaire has only been partially validated in Crohn's disease.
OBJECTIVE: To test the Work Productivity and Activity Impairment questionnaire for use in Crohn's disease patients.
METHODS: A validated Spanish translation of the test was assessed. 'Discriminant validity' was evaluated by comparing Work Productivity and Activity Impairment scores in Crohn's disease patients with active versus inactive disease, and in patients versus healthy controls. 'Convergent validity' was tested comparing Work Productivity and Activity Impairment questionnaire with quality of life, Crohn's disease activity index and a debriefing questionnaire. 'Reproducibility' of repeated tests was evaluated by comparing two Work Productivity and Activity Impairment measures obtained 2 weeks apart in stable patients. 'Responsiveness' was determined by comparing Work Productivity and Activity Impairment values in the same patients during a flare-up of Crohn's disease and during remission. The Wilcoxon test for paired data and the Mann-Whitney U test for unpaired data were used for comparisons.
RESULTS: One hundred and six patients were included in the various steps of the analysis. All Work Productivity and Activity Impairment parameters showed adequate discriminant and convergent validity and responsiveness. The test's reproducibility was also adequate, except for the evaluation of presenteeism (the impairment of productivity while working).
CONCLUSION: The Spanish Work Productivity and Activity Impairment questionnaire is a valid and reliable measurement of work impairment in Crohn's disease. Unexpectedly, the test did not present satisfactory reproducibility for the evaluation of presenteeism. The reliability of this last finding should be evaluated in further studies.