Development and Validation of the iDI: A Short Self-Rating Disability Instrument for Low Back Pain Disorders

STUDY DESIGN: Cross-sectional and longitudinal validation study. OBJECTIVE: Development and validation of a short, reliable, and valid questionnaire for the assessment of low back pain–related disability. METHODS: The iDI was created in a stepwise procedure: (1) its development was based on the literature and theoretical consideration; (2) outcome data were collected and evaluated in a pilot study; (3) final validations were performed based on an international multicenter spine surgery outcome study including 514 patients; (4) the iDI was programmed for a tablet computer (iPad) and tested for its clinical practicability. RESULTS: The final version of the iDI comprises of 8 simple questions related to different aspects of disability with a 5-point Likert-type answer scale. The iDI compared very well to the Oswestry Disability Index in terms of reliability and validity. The iDI was demonstrated to be suitable for data assessment on a tablet computer (iPad). CONCLUSIONS: The iDI is a short, valid, and practicable tool that facilitates routine quality assessment in terms of low back pain–related disability.