IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

Study of the Psychometric Properties of the Work Disability Diagnosis Interview (WoDDI) for Workers with a Musculoskeletal or Common Mental Disorder


The Work Disability Diagnosis Interview (WoDDI) consists of a structured interview designed to help clinicians systematically identify the factors contributing to a work disability. It is one of few tools available in rehabilitation for use with individuals in the chronic phase of work disability. It takes into account the influence of various systems (personal, health care, workplace, and compensation), and was developed for the two main health problems associated with work disability: musculoskeletal disorders (MSDs) and common mental disorders (CMDs).

The aim of this study was to validate the WoDDI with individuals absent from work due to an MSD or a CMD. More specifically, it sought to describe the following psychometric properties of the instrument: (1) construct validity, (2) internal consistency, (3) interrater reliability, and (4) convergent validity.

A cross-sectional correlational design was used with a non-probability sample. The inclusion criteria for occupational therapists were (1) membership in the Ordre des ergothérapeutes du Québec, (2) at least one year’s experience in work rehabilitation, and (3) prior specific training in the use of the WoDDI (average duration of four hours). The inclusion criteria for workers were (1) being absent from work for at least three months but less than two years due to an MSD or a CMD, (2) having a contractual relationship with their employer, and (3) being enrolled in a rehabilitation program. It took between 90 and 120 minutes to administer the WoDDI. In addition, for the purpose of evaluating the instrument’s convergent validity, the participants completed self-report questionnaires measuring various related concepts. For a sub-group of participating workers, the occupational therapists also completed (between 24 and 72 hours after administering the WoDDI) an inventory of causes of work disability maintenance (n=72 for the MSD version and n=65 for the CMD version). Lastly, to assess interrater reliability for the two populations under study, six occupational therapists used the WoDDI to score standardized case histories.

In total, 35 occupational therapists took part in the evaluation of 290 participating workers, including 140 with an MSD and 150 with a CMD. Regarding the exploratory factor analysis (EFA) of the instrument’s construct validity, the results revealed similar dimensions in both versions, specifically, illness representation, clinical judgment of the seriousness of the medical condition, and high levels of work demands. This analysis made it possible to reduce the number of items in the instrument by approximately 20 to 40%, depending on the version. However, the varying results obtained from the EFA for the internal consistency of certain dimensions suggest certain limitations, mainly for the version designed for the CMD population. Interrater reliability was satisfactory as regards the nature of the instrument (i.e., a structured interview). Lastly, given the lack of a standard measure, the convergent validity still has to be confirmed.

In summary, despite the WoDDI’s reported limitations, by reducing the number of items included, its content appears to correlate well with the current scientific literature on the two populations under study. It also fits in with a biopsychosocial understanding of individuals on work disability. However, the CMD version of the instrument requires revision and retesting.