Validity, reliability, and responsiveness of the work productivity and activity impairment questionnaire in Crohn's disease

Abstract

Background: Crohn's disease (CD) is a chronic inflammatory bowel disease usually diagnosed in early adult life and characterized by unpredictable flares and debilitating symptoms such as diarrhea, abdominal pain, and fever, which can interfere with a patient's ability to work and perform daily activities.Objective: The aim of this study was to assess the validity, reliability, and responsiveness of the Work Productivity and Activity Impairment questionnaire in CD (WPAI:CD).Methods: The WPAI:CD was tested in CD patients enrolled in a 26-week randomized clinical trial of cer-tolizumab pegol versus placebo. Discriminative validity of WPAI:CD absenteeism, presenteeism(reduced on-the-job effectiveness), overall work productivity loss (absenteeism + presenteeism), and activity impairment scores was assessed relative to 5 measures of disease severity and health status: CD Activity Index (CDAI), Short Form-36 physical component summary (PCS) and mental health component summary (MCS) scores, Inflammatory Bowel Disease Questionnaire (IBDQ), and the 5-dimensional EuroQoL health-related quality-of-life visual analog scale (EQ-VAS). Responsiveness was assessed by comparing changes in WPAI:CD scores from baseline to week 26 for patients in remission (CDAI <150 points) versus no remission. Standardized Response Means (SRMs) were calculated to evaluate the magnitude of the changes.Results: A total of 662 patients (mean [range] age, 37.4 [18–77] years; male, 288 [43.5%]; white, 629 [95.0%]) were enrolled in the study. Patients with CD of the worst severity (CDAI > median) showed significantly higher impairment in work (+10.5%) and activities (+10.4%) versus patients with "best health" (no problems) (both, P ≤ 0.001). Patients with "worst" IBDQ, PCS, MCS, and EQ-VAS scores also showed significantly higher impairments in work (IBDQ, VAS -24.2%; PCS, -24.1%; MCS, -15.9%; EQ-VAS, -16.5%) and activities (IBDQ, -23.3%; PCS, -21.8%; MCS, -16.5%; EQ-VAS, -17.2%) versus "best" scores (all, P < 0.05). There were significant differences between WPAI:CD impairment scores for patients in remission versus patients failing to achieve remission (P < 0.05). SRMs were small (ie, <0.5) in the nonre-mission group, and moderate to large (ie, >0.5) for patients in remission.Conclusions: The discriminative validity, reliability, and responsiveness of the WPAI:CD were demonstrated. The WPAI:CD may be useful for evaluating drug impact on CD.