Prognostic factors for time receiving workers' compensation benefits in a cohort of patients with low back pain

Study Design. Prospective inception cohort study. Objective. To develop a prognostic model that predicts time receiving worke rs' compensation benefits for low back pain claimants. Summary of Background Data. As the cost and difficulty of managing low back pain escalate, any predictor of outcome is advantageous. Methods. To obtain the outcome and predictor variables, patient data from t wo separate databases were linked: a clinical database and an administrativ e (Ontario workers' compensation) database. Claimants injured between Janua ry 1 and December 31, 1994, were included and observed for 1 year from the date of accident. The outcome variable was cumulative number of calendar da ys receiving benefits. Results. Multivariable Cox proportional hazards regression (forward stepwis e) showed eight significant predictors; five were associated with increased time receiving benefits compared with their reference groups: 1) working i n the construction industry, 2) older age, 3) lag time from injury to treat ment, 4) pain referred into the leg, and 5) three or more positive Waddell nonorganic signs. Three predictors were associated with reduced time receiv ing benefits: 1) higher values of questionnaire score, 2) intermittent pain , and 3) a previous episode of back pain. A predictive score was calculated to categorize claimants as at high or low risk for chronicity. When an arb itrary cutoff point was set at the 75th percentile of predictive score, neg ative predictive value was 94%. Conclusion. This research identified eight factors for time receiving worke rs' compensation benefits among claimants with low back pain. This model di scriminates between high- and low-risk claimants. Few low-risk claimants co ntinued to receive benefits for more than 3 months.