Identifying factors associated with physical therapy use versus non-use among injured workers with back pain in Washington State.

Background: There is little information about predictors of physical therapy (PT) use among injured workers with back pain. The primary objective of this study is to investigate the associations between PT use and baseline factors not routinely captured in workers' compensation (WC) data.

Methods: We conducted a secondary analysis using the Washington State Workers' Compensation Disability Risk Identification Study Cohort, which combines self-reported surveys with claims data from the Washington State Department of Labor and Industries State Fund. Workers with an accepted or provisional WC claim for back injury between June 2002 and April 2004 were eligible. Baseline factors for PT use were selected from six domains (socio-demographic, pain and function, psychosocial, clinical, health behaviors, and employment-related). The outcome was a binary measure for PT use within 1 year of injury. Bivariate and multivariable logistic regression models were conducted to evaluate the associations between PT use and baseline factors.

Results: Among the 1370 eligible study participants, we identified 673 (49%) who received at least one PT service. Baseline factors from five of the six domains (all but health behaviors) were associated with PT use, including gender, income, pain and function measures, injury severity rating, catastrophizing, recovery expectations, fear avoidance, mental health score, body mass index, first provider seen for injury, previous injury, and several work-related factors.

Conclusion: We identify baseline factors that are associated with PT use, which may be useful in addressing disparities in access to care for injured workers with back pain in a WC system.