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Construct and predictive validity of the chronic pain grade in workers with chronic work-related upper-extremity
Jean-Sébastien Roy1, Joy C MacDermid, Kenneth Tang
1*Department of Rehabilitation, Faculty of Medicine, Laval University †Centre for Interdisciplinary Research in Rehabilitation and Social Integration, Quebec Rehabilitation Institute, Quebec City, QC ‡School of Rehabilitation Science, McMaster University, Hamilton §Hand and Upper Limb Centre, St Joseph's Health Centre, London ∥Mobility Program Clinical Research Unit, St Michael's Hospital ¶Institute of Health Policy, Management and Evaluation, University of Toronto #Institute for Work & Health **Department of Occupational Science and Occupational Therapy, University of Toronto, Toronto, ON, Canada.
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.
