Validation of the Work Disability Diagnosis Interview for Musculoskeletal and Mental Disorders

Purpose The Work Disability Diagnosis Interview (WoDDI) consists of a semi-structured interview designed to help clinicians systematically identify the factors contributing to a work disability. The aim was to validate two versions of the WoDDI (construct validity, internal consistency, interrater reliability) developed for individuals absent from work due to a musculoskeletal disorder (MSD) or common mental disorder (CMD). Methods A convenience sample of workers absent from work for at least three months due to an MSD or a CMD and enrolled in a rehabilitation program was recruited. To assess interrater reliability for the MSD and CMD versions, six occupational therapists by sub-group scored the WoDDI based on case histories. Results A total of 290 male and female workers (140 MSD, 150 CMD) were recruited. Exploratory factor analysis revealed similar dimensions in both versions, specifically, illness representation, clinical judgment of the complexity of the medical condition, and high level of work demands. It allowed items to be reduced by approximately 20 and 40% respectively for the CMD and MSD versions. Internal consistency (Cronbach's alpha) varied from 0.40 to 0.75 and 0.75 to 0.80 for the CMD and MSD versions respectively, while interrater reliability (Cohen's kappa coefficients) varied from 0.51 to 0.57 and 0.27 to 0.44 for the two versions respectively. Conclusion Despite some limitations, the WoDDI's factors correspond to those in the current scientific literature. The varying results for internal consistency suggest limitations mainly for the CMD version. Interrater reliability was found overall to be fair. The next step will be to revise and retest this version.