Construct and predictive validity of the chronic pain grade in workers with chronic work-related upper-extremity disorders

OBJECTIVE:: To evaluate the ability of Chronic Pain Grade (CPG) questionnaire to predict upper-extremity physical disability, at-work disability, and work status in workers with chronic work-related upper-limb injuries. METHODS:: A total of 448 individuals with chronic work-related injuries were assessed at baseline and 6 months later. At each evaluation, 4 self-reported questionnaires were completed (CPG, QuickDASH, Work Limitations Questionnaire, and Work Instability Scale), and current work status was evaluated. Predictive validity of CPG was evaluated using proportion tests. RESULTS:: At baseline, 5% of participants had a CPG at Grade I, 7% at grade II, 18% at Grade III, and 70% at Grade IV (high disability-severely limiting). Twenty-six percent of workers transitioned in terms of their work status (7% from not working to working, 19% working to not working). Higher Grades on CPG at baseline could not predict improvement or deterioration 6 months after for upper-extremity disability (QuickDASH), at-work productivity loss (Work Limitations Questionnaire), or work instability (Work Instability Scale). Initial CPG could predict 6-month work status in the full sample. However, when considering only participants not working at baseline, CPG did not predict return to work. DISCUSSION:: CPG has low to moderate ability to predict 6-month work status in patients with chronic upper-extremity disorders. Both a lack of CPG and work transition variability may have contributed to this finding. Extension of the upper end of CPG range might be investigated as a means to increase discrimination at the upper end spectrum of chronic pain, which predominate the population of patients with chronic musculoskeletal disorders