Disability Risk in Work-Related Musculoskeletal Injuries.

摘要

The vast majority of costs and lost productivity in workers' compensation are due to work-related musculoskeletal injuries. Among injured workers with these conditions, a small proportion (5-10%) develop long-term disability and account for most (80-85%) of the cost and lost work. Low back pain and carpal tunnel syndrome (CTS) are the most common musculoskeletal conditions associated with long-term work disability. If accurate methods of early identification of workers at high risk for chronic disability could be linked to effective early intervention, substantial secondary (disability) prevention could be achieved. In the absence of an accurate method to identify workers at risk for long-term disability, secondary prevention efforts cannot be well-targeted. We have completed a population-based prospective study with the principal aim of developing models of accurate long-term disability risk identification for work-related injuries involving low back pain or CTS. We hypothesized that an accurate predictive model of risk for long-term disability would include factors both intrinsic (severity of injury, self-reported pain and function, psychosocial factors) and extrinsic (employment, administrative, and health care factors) to the worker. The ultimate goal was to develop a brief screening questionnaire that could be administered within a few weeks of injury and pilot-tested in real world clinical situations. Prior to the initiation of this study, no such accurate method of risk identification had been fully developed or tested. The prospective cohort design involved baseline collection of both computerized claim data (e.g., demographics, administrative variables) and worker self-report data (e.g., pain, physical function, psychosocial factors, work exposure factors). In addition, worker medical records from visits in the first few weeks after injury were reviewed to assign injury severity ratings developed and assessed in an early phase of the study. The low back injury severity rating was found to have good inter-rater reliability. The principal outcome variable was wage replacement status (on/off) at one year (low back) or >180 days lost work time in one year (CTS). For both conditions, univariate and multivariate logistic regression analyses were used to identify the strongest predictors of outcome. In addition, classification and regression tree (CART) analysis was used to develop a parsimonious predictive model that could be translated into a brief screening questionnaire. The final analysis samples consisted of 1,885 workers with low back pain and 899 workers with CTS. Interviews were completed at a median of 18 days following claim receipt. For low back pain, the final multivariable predictive model included injury severity (rated from medical records), specialty of the first health care provider seen for the injury (obtained from administrative data), and worker-reported (during the baseline interview) physical disability (Roland-Morris Disability Questionnaire), number of pain sites, "very hectic" job, no offer of a job accommodation, and previous injury involving a month or more off work. The model showed good ability to discriminate between workers who were disabled at one year and those who were not [area under the receiver operating characteristic curve (AUC) = 0.84]. For CTS, the final multivariable prediction model (AUC = 0.76) included age, functional status score on a self-report questionnaire, employer offer of job accommodation, job physical demands, and recovery expectations. These findings underscore the importance of factors across different domains in predicting long-term disability risk, and of factors extrinsic as well as intrinsic to the worker. In the final CART model for low back pain, three baseline worker self-report variables were highly predictive of one-year disability: not working in the past week, rating of pain interference with work (>5 on a 0-10 scale), and pain radiating into the leg. In the final CART model for CTS, work status at baseline was the only strong predictor of the one-year disability outcome measure. Based on these results, we developed a brief ( 6-question) questionnaire to identify, soon after a back injury, workers who are at high risk for long-term disability. At recent meetings with community occupational health clinical leaders in both Eastern and Western Washington, we presented the questionnaire and invited comments. There is high interest (from approximately 20 providers) in piloting the questionnaire, and in linking the use of the questionnaire with interventions based on worker responses.