Reliability and Construct Validity of the Work Rehabilitation Questionnaire Domains in Patients with Persistent Low Back Pain.

Purpose: The Work Rehabilitation Questionnaire (WORQ) assesses patient functioning, including psychological, physical, and cognitive limitations. This study evaluates the WORQ domains in individuals with persistent low back pain (LBP), focusing on reliability and construct validity.

Methods: Individuals aged 18-65 with LBP completed WORQ and the workability index single item. A subgroup undertook sit-to-stand and 6-min walking tests and re-evaluated WORQ after 14 days. Reliability was assessed through internal consistency (McDonald's omega and Cronbach's alpha), test-retest reliability, and smallest detectable change. Construct validity was analyzed via Spearman's rank correlation and known group validity, with physical functioning also examined against sit-to-stand and 6-min walk test results for sensitivity/specificity. Floor and ceiling effects were assessed through classical and scale width methods.

Results: Of 425 participants, 149 completed physical tests, and 102 re-assessed WORQ. McDonald's omega and Cronbach's alpha indicated high internal consistency (0.92-0.96) with strong test-retest reliability (intraclass-correlation coefficients: 0.74-0.82). The smallest detectable change ranged from 4.62 to 7.82. Predictions from 7 out of 8 hypotheses were confirmed. Notable differences in domain scores were observed based on disability level and sick leave status, with varied diagnostic performance in physical functioning items. Potential floor effects were noted using the scale width method.

Conclusions: The WORQ demonstrated good reliability and satisfactory validity in assessing work-related functioning in individuals with persistent LBP. These findings support its use as a comprehensive tool for evaluating psychological, physical, and cognitive limitations. However, varied diagnostic performance in physical functioning items and potential floor effects suggest cautious interpretation in diverse clinical settings.