Self-reported severity measures as predictors of return-to-work outcomes in occupational back pain

Introduction: We test an array of biopsychosocial, cognitive-behavioral, and work-related factors to identify the best predictors of work disability following a back injury. Methods: We test the validity of alternative severity measures in predicting the likelihood of four distinct, mutually exclusive patterns of post-injury employment in the first year after onset of back pain. The study sample includes 959 participants in the ASU Healthy Back Study, a prospective cohort study of workers who filed claims for occupational back pain between 1999 and 2002. Self-reported severity measures include: NRS-101 measures of the intensity of back or leg pain, Roland-Morris scale of functional disability, and mental and physical components of the SF-12. Results: All the severity measures have significant predictive power on return-to-work outcomes even after 1 year. Baseline physical functioning and overall mental and physical health status are more predictive of specific patterns of post-injury employment than pain intensity measures, possibly because there is considerable idiosyncratic variation in the pain intensity measures. The mental component of the SF-12, in particular, is relatively robust to alternate specifications, consistently statistically significant, and has the lowest probability significance level in explaining patterns of employment 1 year after injury.